style: fix rubocop offenses

Co-Authored-By: Claude Opus 4.5 <[email protected]>

.github/dependabot.yaml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly

.github/workflows/liquid.yml

@@ -1,5 +1,5 @@
 name: Liquid
-on: [push, pull_request]
+on: [push]
 
 env:
   BUNDLE_JOBS: 4
@@ -9,29 +9,64 @@ jobs:
   test:
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         entry:
-          - { ruby: 3.0, allowed-failure: false } # minimum supported
-          - { ruby: 3.2, allowed-failure: false }
-          - { ruby: 3.3, allowed-failure: false }
-          - { ruby: 3.4, allowed-failure: false } # latest
-          - { ruby: ruby-head, allowed-failure: false }
-    name: Test Ruby ${{ matrix.entry.ruby }}
+          - { ruby: 3.3, allowed-failure: false } # minimum supported
+          - { ruby: 3.4, allowed-failure: false, rubyopt: "--yjit" }
+          - { ruby: 4.0, allowed-failure: false } # latest stable
+          - {
+              ruby: 4.0,
+              allowed-failure: false,
+              rubyopt: "--enable-frozen-string-literal",
+            }
+          - { ruby: 4.0, allowed-failure: false, rubyopt: "--yjit" }
+          - { ruby: 4.0, allowed-failure: false, rubyopt: "--zjit" }
+
+          # Head can have failures due to being in development
+          - { ruby: head, allowed-failure: true }
+          - {
+              ruby: head,
+              allowed-failure: true,
+              rubyopt: "--enable-frozen-string-literal",
+            }
+          - { ruby: head, allowed-failure: true, rubyopt: "--yjit" }
+          - { ruby: head, allowed-failure: true, rubyopt: "--zjit" }
+    name: Test Ruby ${{ matrix.entry.ruby }} ${{ matrix.entry.rubyopt }} --${{ matrix.entry.allowed-failure && 'allowed-failure' || 'strict' }}
     steps:
-      - uses: actions/checkout@v3
-      - uses: ruby/setup-ruby@v1
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
+      - uses: ruby/setup-ruby@a25f1e45f0e65a92fcb1e95e8847f78fb0a7197a # v1.273.0
         with:
           ruby-version: ${{ matrix.entry.ruby }}
           bundler-cache: true
           bundler: latest
       - run: bundle exec rake
         continue-on-error: ${{ matrix.entry.allowed-failure }}
+        env:
+          RUBYOPT: ${{ matrix.entry.rubyopt }}
+
+  spec:
+    runs-on: ubuntu-latest
+    env:
+      BUNDLE_WITH: spec
+    steps:
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
+      - uses: ruby/setup-ruby@a25f1e45f0e65a92fcb1e95e8847f78fb0a7197a # v1.273.0
+        with:
+          bundler-cache: true
+          bundler: latest
+      - name: Run liquid-spec for all adapters
+        run: |
+          for adapter in spec/*.rb; do
+            echo "=== Running $adapter ==="
+            bundle exec liquid-spec run "$adapter" --no-max-failures
+          done
 
   memory_profile:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: ruby/setup-ruby@v1
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
+      - uses: ruby/setup-ruby@a25f1e45f0e65a92fcb1e95e8847f78fb0a7197a # v1.273.0
         with:
           bundler-cache: true
       - run: bundle exec rake memory_profile:run

.rubocop_todo.yml

@@ -174,7 +174,16 @@ Style/WordArray:
 
 # Offense count: 117
 # This cop supports safe auto-correction (--auto-correct).
-# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, AllowedPatterns, IgnoredPatterns.
+# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, AllowCopDirectives, AllowedPatterns.
 # URISchemes: http, https
 Layout/LineLength:
   Max: 260
+
+Naming/PredicatePrefix:
+  Enabled: false
+
+# Offense count: 1
+# This is intentional - early return from begin/rescue in assignment context
+Lint/NoReturnInBeginEndBlocks:
+  Exclude:
+    - 'lib/liquid/standardfilters.rb'

CONTRIBUTING.md

@@ -29,6 +29,8 @@
 
 ## Releasing
 
-* Bump the version in `lib/liquid/version.rb` and merge it on `main`
+* Bump the version in `lib/liquid/version.rb`
+* Update the `History.md` file
+* Open a PR like [this one](https://github.com/Shopify/liquid/pull/1894) and merge it to `main`
 * Create a new release using the [GitHub UI](https://github.com/Shopify/liquid/releases/new)
 

Gemfile

@@ -20,8 +20,19 @@ group :benchmark, :test do
   end
 end
 
+group :development do
+  gem "webrick"
+end
+
 group :test do
-  gem 'rubocop', '~> 1.61.0'
-  gem 'rubocop-shopify', '~> 2.12.0', require: false
+  gem 'benchmark'
+  gem 'rubocop', '~> 1.82.0'
+  gem 'rubocop-shopify', '~> 2.18.0', require: false
   gem 'rubocop-performance', require: false
 end
+
+group :spec do
+  # TODO: temporary - using cp-gate-lax-specs-ai branch until lax specs are properly gated
+  gem 'liquid-spec', github: 'Shopify/liquid-spec', branch: 'cp-gate-lax-specs-ai'
+  gem 'activesupport', require: false
+end

History.md

@@ -1,12 +1,129 @@
 # Liquid Change Log
 
-## 5.6.0 (unreleased)
+## 6.0.0
+
+### Features
+* (TODO) Add support for boolean expressions everywhere
+  * As variable output `{{ a or b }}`
+  * As filter argument `{{ collection | where: 'prop', a or b }}`
+  * As tag argument `{% render 'snip', enabled: a or b %}`
+  * As conditional tag argument `{% if cond %}` (extending previous behaviour)
+* (TODO) Add support for subexpression prioritization and associativity
+  * In ascending order of priority:
+    * Logical: `and`, `or` (right to left)
+    * Equality: `==`, `!=`, `<>` (left to right)
+    * Comparison: `>`, `>=`, `<`, `<=`, `contains` (left to right)
+  - For example, this is now supported
+    * `{{ a > b == c < d or e == f }}` which is equivalent to
+    * `{{ ((a > b) == (c < d)) or (e == f) }}`
+- (TODO) Add support for parenthesized expressions
+  * e.g. `(a or b) and c`
+
+### Architectural changes
+* `parse_expression` and `safe_parse_expression` have been removed from `Tag` and `ParseContext`
+* `Parser` methods now produce AST nodes instead of strings
+  * `Parser#expression` produces a value,
+  * `Parser#string` produces a string,
+  * etc.
+
+### Breaking changes
+* The Environment's `error_mode` option has been removed.
+  * `:warn` is no longer supported
+  * `:lax` and `lax_parse` is no longer supported
+  * `:strict` and `strict_parse` is no longer supported
+  * `strict2_parse` is renamed to `parse_markup`
+* The `warnings` system has been removed.
+* `Parser#expression` is renamed to `Parser#expression_string`
+* `safe_parse_expression` methods are replaced by `Parser#expression`
+* `parse_expression` methods are replaced by `Parser#unsafe_parse_expression`
+
+### Migrating from `^5.11.0`
+- In custom tags that include `ParserSwitching`, rename `strict2_parse` to `parse_markup`
+- Remove code depending on `:error_mode`
+- Replace `safe_parse_expression` calls with `Parser#expression`
+
+## 5.11.0
+* Revert the Inline Snippets tag (#2001), treat its inclusion in the latest Liquid release as a bug, and allow for feedback on RFC#1916 to better support Liquid developers [Guilherme Carreiro]
+* Rename the `:rigid` error mode to `:strict2` and display a warning when users attempt to use the `:rigid` mode [Guilherme Carreiro]
+
+## 5.10.0
+* Introduce support for Inline Snippets [Julia Boutin]
+
+## 5.9.0
+* Introduce `:rigid` error mode for stricter, safer parsing of all tags [CP Clermont, Guilherme Carreiro]
+
+## 5.8.7
+* Expose body content in the `Doc` tag [James Meng]
+
+## 5.8.1
+
+* Fix `{% doc %}` tag to be visitable [Guilherme Carreiro]
+
+## 5.8.0
+
+* Introduce the new `{% doc %}` tag [Guilherme Carreiro]
+
+## 5.7.3
+
+* Raise Liquid::SyntaxError when parsing invalidly encoded strings [Chris AtLee]
+
+## 5.7.2 2025-01-31
+
+* Fix array filters to not support nested properties [Guilherme Carreiro]
+
+## 5.7.1 2025-01-24
+
+* Fix the `find` and `find_index`filters to return `nil` when filtering empty arrays [Guilherme Carreiro]
+* Fix the `has` filter to return `false` when filtering empty arrays [Guilherme Carreiro]
+
+## 5.7.0 2025-01-16
+
+### Features
+
+* Add `find`, `find_index`, `has`, and `reject` filters to arrays [Guilherme Carreiro]
+* Compatibility with Ruby 3.4 [Ian Ker-Seymer]
+
+## 5.6.4 2025-01-14
 
 ### Fixes
+* Add a default `string_scanner` to avoid errors with `Liquid::VariableLookup.parse("foo.bar")` [Ian Ker-Seymer]
 
+## 5.6.3 2025-01-13
+* Remove `lru_redux` dependency [Michael Go]
+
+## 5.6.2 2025-01-13
+
+### Fixes
+* Preserve the old behavior of requiring floats to start with a digit [Michael Go]
+
+## 5.6.1 2025-01-13
+
+### Performance improvements
+* Faster Expression parser / Tokenizer with StringScanner [Michael Go]
+
+## 5.6.0 2024-12-19
+
+### Architectural changes
+* Added new `Environment` class to manage configuration and state that was previously stored in `Template` [Ian Ker-Seymer]
+* Moved tag registration from `Template` to `Environment` [Ian Ker-Seymer]
+* Removed `StrainerFactory` in favor of `Environment`-based strainer creation [Ian Ker-Seymer]
+* Consolidated standard tags into a new `Tags` module with `STANDARD_TAGS` constant [Ian Ker-Seymer]
+
+### Performance improvements
+* Optimized `Lexer` with a new `Lexer2` implementation using jump tables for faster tokenization, requires Ruby 3.4 [Ian Ker-Seymer]
+* Improved variable rendering with specialized handling for different types [Michael Go]
+* Reduced array allocations by using frozen empty constants [Michael Go]
+
+### API changes
+* Deprecated several `Template` class methods in favor of `Environment` methods [Ian Ker-Seymer]
+* Added deprecation warnings system [Ian Ker-Seymer]
+* Changed how filters and tags are registered to use Environment [Ian Ker-Seymer]
+
+### Fixes
+* Fixed table row handling of break interrupts [Alex Coco]
+* Improved variable output handling for arrays [Ian Ker-Seymer]
 * Fix Tokenizer to handle null source value (#1873) [Bahar Pourazar]
 
-
 ## 5.5.0 2024-03-21
 
 Please reference the GitHub release for more information.

README.md

@@ -93,31 +93,6 @@ LIQUID
 
 By using Environments, you ensure that custom tags and filters are only available in the contexts where they are needed, making your Liquid templates more robust and easier to manage. For smaller projects, a global environment is available via `Liquid::Environment.default`.
 
-### Error Modes
-
-Setting the error mode of Liquid lets you specify how strictly you want your templates to be interpreted.
-Normally the parser is very lax and will accept almost anything without error. Unfortunately this can make
-it very hard to debug and can lead to unexpected behaviour.
-
-Liquid also comes with a stricter parser that can be used when editing templates to give better error messages
-when templates are invalid. You can enable this new parser like this:
-
-```ruby
-Liquid::Environment.default.error_mode = :strict
-Liquid::Environment.default.error_mode = :strict # Raises a SyntaxError when invalid syntax is used
-Liquid::Environment.default.error_mode = :warn # Adds strict errors to template.errors but continues as normal
-Liquid::Environment.default.error_mode = :lax # The default mode, accepts almost anything.
-```
-
-If you want to set the error mode only on specific templates you can pass `:error_mode` as an option to `parse`:
-```ruby
-Liquid::Template.parse(source, error_mode: :strict)
-```
-This is useful for doing things like enabling strict mode only in the theme editor.
-
-It is recommended that you enable `:strict` or `:warn` mode on new apps to stop invalid templates from being created.
-It is also recommended that you use it in the template editors of existing apps to give editors better error messages.
-
 ### Undefined variables and filters
 
 By default, the renderer doesn't raise or in any other way notify you if some variables or filters are missing, i.e. not passed to the `render` method.

Rakefile

@@ -33,21 +33,12 @@ task :rubocop do
   end
 end
 
-desc('runs test suite with both strict and lax parsers')
+desc('runs test suite')
 task :test do
-  ENV['LIQUID_PARSER_MODE'] = 'lax'
-  Rake::Task['base_test'].invoke
-
-  ENV['LIQUID_PARSER_MODE'] = 'strict'
   Rake::Task['base_test'].reenable
   Rake::Task['base_test'].invoke
 
   if RUBY_ENGINE == 'ruby' || RUBY_ENGINE == 'truffleruby'
-    ENV['LIQUID_PARSER_MODE'] = 'lax'
-    Rake::Task['integration_test'].reenable
-    Rake::Task['integration_test'].invoke
-
-    ENV['LIQUID_PARSER_MODE'] = 'strict'
     Rake::Task['integration_test'].reenable
     Rake::Task['integration_test'].invoke
   end
@@ -70,19 +61,11 @@ task release: :build do
 end
 
 namespace :benchmark do
-  desc "Run the liquid benchmark with lax parsing"
-  task :lax do
-    ruby "./performance/benchmark.rb lax"
+  desc "Run the liquid benchmark"
+  task :run do
+    ruby "./performance/benchmark.rb"
   end
 
-  desc "Run the liquid benchmark with strict parsing"
-  task :strict do
-    ruby "./performance/benchmark.rb strict"
-  end
-
-  desc "Run the liquid benchmark with both lax and strict parsing"
-  task run: [:lax, :strict]
-
   desc "Run unit benchmarks"
   namespace :unit do
     task :all do
@@ -113,11 +96,6 @@ namespace :profile do
   task :run do
     ruby "./performance/profile.rb"
   end
-
-  desc "Run the liquid profile/performance coverage with strict parsing"
-  task :strict do
-    ruby "./performance/profile.rb strict"
-  end
 end
 
 namespace :memory_profile do
@@ -135,3 +113,9 @@ end
 task :console do
   exec 'irb -I lib -r liquid'
 end
+
+desc('run liquid-spec suite across all adapters')
+task :spec do
+  adapters = Dir['./spec/*.rb'].join(',')
+  sh "bundle exec liquid-spec matrix --adapters=#{adapters} --reference=ruby_liquid"
+end

bin/render

@@ -0,0 +1,46 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'bundler/setup'
+require 'liquid'
+
+class VirtualFileSystem
+  def initialize
+    snippet_1 = <<~LIQUID
+      <h1>
+        {{- greating | default: 'Hello' }}, {{ name | default: 'world' -}}!
+      </h1>
+    LIQUID
+    snippet_2 = <<~LIQUID
+      {%- for i in (1..5) -%}
+        > {{ i }}
+      {%- endfor -%}
+    LIQUID
+
+    @templates = {
+      'snippet-1' => snippet_1,
+      'snippet-2' => snippet_2,
+    }
+  end
+
+  def read_template_file(key)
+    @templates[key] || raise(Liquid::FileSystemError, "No such template '#{key}'")
+  end
+end
+
+def source
+  File.read(ARGV[0])
+rescue StandardError
+  'Usage: bin/render example/server/templates/index.liquid'
+end
+
+def assigns
+  {
+    'date' => Time.now,
+  }
+end
+
+puts Liquid::Template
+  .parse(source, error_mode: :strict2)
+  .tap { |t| t.registers[:file_system] = VirtualFileSystem.new }
+  .render(assigns)

lib/liquid/condition.rb

@@ -48,8 +48,9 @@ module Liquid
       @@operators
     end
 
-    def self.parse_expression(parse_context, markup)
-      @@method_literals[markup] || parse_context.parse_expression(markup)
+    def self.parse_expression(parser)
+      markup = parser.expression_string
+      @@method_literals[markup] || parser.unsafe_parse_expression(markup)
     end
 
     attr_reader :attachment, :child_condition
@@ -113,24 +114,67 @@ module Liquid
 
     def equal_variables(left, right)
       if left.is_a?(MethodLiteral)
-        if right.respond_to?(left.method_name)
-          return right.send(left.method_name)
-        else
-          return nil
-        end
+        return call_method_literal(left, right)
       end
 
       if right.is_a?(MethodLiteral)
-        if left.respond_to?(right.method_name)
-          return left.send(right.method_name)
-        else
-          return nil
-        end
+        return call_method_literal(right, left)
       end
 
       left == right
     end
 
+    def call_method_literal(literal, value)
+      method_name = literal.method_name
+
+      # If the object responds to the method (e.g., ActiveSupport is loaded), use it
+      if value.respond_to?(method_name)
+        value.send(method_name)
+      else
+        # Emulate ActiveSupport's blank?/empty? to make Liquid invariant
+        # to whether ActiveSupport is loaded or not
+        case method_name
+        when :blank?
+          liquid_blank?(value)
+        when :empty?
+          liquid_empty?(value)
+        else
+          false
+        end
+      end
+    end
+
+    # Implement blank? semantics matching ActiveSupport
+    # blank? returns true for nil, false, empty strings, whitespace-only strings,
+    # empty arrays, and empty hashes
+    def liquid_blank?(value)
+      case value
+      when NilClass, FalseClass
+        true
+      when TrueClass, Numeric
+        false
+      when String
+        # Blank if empty or whitespace only (matches ActiveSupport)
+        value.empty? || value.match?(/\A\s*\z/)
+      when Array, Hash
+        value.empty?
+      else
+        # Fall back to empty? if available, otherwise false
+        value.respond_to?(:empty?) ? value.empty? : false
+      end
+    end
+
+    # Implement empty? semantics
+    # Note: nil is NOT empty. empty? checks if a collection has zero elements.
+    def liquid_empty?(value)
+      case value
+      when String, Array, Hash
+        value.empty?
+      else
+        value.respond_to?(:empty?) ? value.empty? : false
+      end
+    end
+
     def interpret_condition(left, right, op, context)
       # If the operator is empty this means that the decision statement is just
       # a single variable. We can just poll this variable from the context and
@@ -154,8 +198,8 @@ module Liquid
     end
 
     def deprecated_default_context
-      warn("DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated" \
-        " and will be removed from Liquid 6.0.0.")
+      warn("DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated " \
+        "and will be removed from Liquid 6.0.0.")
       Context.new
     end
 

lib/liquid/context.rb

@@ -60,10 +60,6 @@ module Liquid
     end
     # rubocop:enable Metrics/ParameterLists
 
-    def warnings
-      @warnings ||= []
-    end
-
     def strainer
       @strainer ||= @environment.create_strainer(self, @filters)
     end
@@ -157,7 +153,6 @@ module Liquid
         subcontext.filters  = @filters
         subcontext.strainer = nil
         subcontext.errors   = errors
-        subcontext.warnings = warnings
         subcontext.disabled_tags = @disabled_tags
       end
     end
@@ -180,11 +175,12 @@ module Liquid
     # Example:
     #   products == empty #=> products.empty?
     def [](expression)
-      evaluate(Expression.parse(expression, @string_scanner))
+      @string_scanner.string = expression
+      evaluate(Parser.new(@string_scanner).expression)
     end
 
     def key?(key)
-      self[key] != nil
+      find_variable(key, raise_on_not_found: false) != nil
     end
 
     def evaluate(object)
@@ -244,7 +240,7 @@ module Liquid
 
     protected
 
-    attr_writer :base_scope_depth, :warnings, :errors, :strainer, :filters, :disabled_tags
+    attr_writer :base_scope_depth, :errors, :strainer, :filters, :disabled_tags
 
     private
 

lib/liquid/drop.rb

@@ -31,7 +31,7 @@ module Liquid
 
     # Catch all for the method
     def liquid_method_missing(method)
-      return nil unless @context&.strict_variables
+      return unless @context&.strict_variables
       raise Liquid::UndefinedDropMethod, "undefined method #{method}"
     end
 

lib/liquid/environment.rb

@@ -4,10 +4,6 @@ module Liquid
   # The Environment is the container for all configuration options of Liquid, such as
   # the registered tags, filters, and the default error mode.
   class Environment
-    # The default error mode for all templates. This can be overridden on a
-    # per-template basis.
-    attr_accessor :error_mode
-
     # The tags that are available to use in the template.
     attr_accessor :tags
 
@@ -33,17 +29,14 @@ module Liquid
       #  the template.
       # @param file_system The default file system that is used
       #  to load templates from.
-      # @param error_mode [Symbol] The default error mode for all templates
-      #  (either :strict, :warn, or :lax).
       # @param exception_renderer [Proc] The exception renderer that is used to
       #   render exceptions.
       # @yieldparam environment [Environment] The environment instance that is being built.
       # @return [Environment] The new environment instance.
-      def build(tags: nil, file_system: nil, error_mode: nil, exception_renderer: nil)
+      def build(tags: nil, file_system: nil, exception_renderer: nil)
         ret = new
         ret.tags = tags if tags
         ret.file_system = file_system if file_system
-        ret.error_mode = error_mode if error_mode
         ret.exception_renderer = exception_renderer if exception_renderer
         yield ret if block_given?
         ret.freeze
@@ -75,7 +68,6 @@ module Liquid
     # @api private
     def initialize
       @tags = Tags::STANDARD_TAGS.dup
-      @error_mode = :lax
       @strainer_template = Class.new(StrainerTemplate).tap do |klass|
         klass.add_filter(StandardFilters)
       end

lib/liquid/expression.rb

@@ -11,9 +11,6 @@ module Liquid
       'false' => false,
       'blank' => '',
       'empty' => '',
-      # in lax mode, minus sign can be a VariableLookup
-      # For simplicity and performace, we treat it like a literal
-      '-' => VariableLookup.parse("-", nil).freeze,
     }.freeze
 
     DOT = ".".ord
@@ -51,72 +48,35 @@ module Liquid
       end
 
       def inner_parse(markup, ss, cache)
-        if (markup.start_with?("(") && markup.end_with?(")")) && markup =~ RANGES_REGEX
-          return RangeLookup.parse(
-            Regexp.last_match(1),
-            Regexp.last_match(2),
-            ss,
-            cache,
+        if markup.start_with?("(") && markup.end_with?(")") && markup =~ RANGES_REGEX
+          start_markup = Regexp.last_match(1)
+          end_markup = Regexp.last_match(2)
+          start_obj = parse(start_markup, ss, cache)
+          end_obj = parse(end_markup, ss, cache)
+          return RangeLookup.create(
+            start_obj,
+            end_obj,
+            start_markup,
+            end_markup,
           )
         end
 
-        if (num = parse_number(markup, ss))
+        if (num = parse_number(markup))
           num
         else
           VariableLookup.parse(markup, ss, cache)
         end
       end
 
-      def parse_number(markup, ss)
+      def parse_number(markup)
         # check if the markup is simple integer or float
         case markup
         when INTEGER_REGEX
-          return Integer(markup, 10)
+          Integer(markup, 10)
         when FLOAT_REGEX
-          return markup.to_f
-        end
-
-        ss.string = markup
-        # the first byte must be a digit or  a dash
-        byte = ss.scan_byte
-
-        return false if byte != DASH && (byte < ZERO || byte > NINE)
-
-        if byte == DASH
-          peek_byte = ss.peek_byte
-
-          # if it starts with a dash, the next byte must be a digit
-          return false if peek_byte.nil? || !(peek_byte >= ZERO && peek_byte <= NINE)
-        end
-
-        # The markup could be a float with multiple dots
-        first_dot_pos = nil
-        num_end_pos = nil
-
-        while (byte = ss.scan_byte)
-          return false if byte != DOT && (byte < ZERO || byte > NINE)
-
-          # we found our number and now we are just scanning the rest of the string
-          next if num_end_pos
-
-          if byte == DOT
-            if first_dot_pos.nil?
-              first_dot_pos = ss.pos
-            else
-              # we found another dot, so we know that the number ends here
-              num_end_pos = ss.pos - 1
-            end
-          end
-        end
-
-        num_end_pos = markup.length if ss.eos?
-
-        if num_end_pos
-          # number ends with a number "123.123"
-          markup.byteslice(0, num_end_pos).to_f
+          markup.to_f
         else
-          # number ends with a dot "123."
-          markup.byteslice(0, first_dot_pos).to_f
+          false
         end
       end
     end

lib/liquid/i18n.rb

@@ -28,7 +28,7 @@ module Liquid
     def interpolate(name, vars)
       name.gsub(/%\{(\w+)\}/) do
         # raise TranslationError, "Undefined key #{$1} for interpolation in translation #{name}"  unless vars[$1.to_sym]
-        (vars[Regexp.last_match(1).to_sym]).to_s
+        vars[Regexp.last_match(1).to_sym].to_s
       end
     end
 

lib/liquid/lexer.rb

@@ -161,6 +161,12 @@ module Liquid
         end
         # rubocop:enable Metrics/BlockNesting
         output << EOS
+      rescue ::ArgumentError => e
+        if e.message == "invalid byte sequence in #{ss.string.encoding}"
+          raise SyntaxError, "Invalid byte sequence in #{ss.string.encoding}"
+        else
+          raise
+        end
       end
 
       def raise_syntax_error(start_pos, ss)

lib/liquid/locales/en.yml

@@ -2,12 +2,14 @@
   errors:
     syntax:
       tag_unexpected_args: "Syntax Error in '%{tag}' - Valid syntax: %{tag}"
+      block_tag_unexpected_args: "Syntax Error in '%{tag}' - Valid syntax: {% %{tag} %}{% end%{tag} %}"
       assign: "Syntax Error in 'assign' - Valid syntax: assign [var] = [source]"
       capture: "Syntax Error in 'capture' - Valid syntax: capture [var]"
       case: "Syntax Error in 'case' - Valid syntax: case [condition]"
       case_invalid_when: "Syntax Error in tag 'case' - Valid when condition: {% when [condition] [or condition2...] %}"
       case_invalid_else: "Syntax Error in tag 'case' - Valid else condition: {% else %} (no parameters) "
       cycle: "Syntax Error in 'cycle' - Valid syntax: cycle [name :] var [, var2, var3 ...]"
+      doc_invalid_nested: "Syntax Error in 'doc' - Nested doc tags are not allowed"
       for: "Syntax Error in 'for loop' - Valid syntax: for [item] in [collection]"
       for_invalid_in: "For loops require an 'in' clause"
       for_invalid_attribute: "Invalid attribute in for loop. Valid attributes are limit and offset"
@@ -18,6 +20,7 @@
       invalid_template_encoding: "Invalid template encoding"
       render: "Syntax error in tag 'render' - Template name must be a quoted string"
       table_row: "Syntax Error in 'table_row loop' - Valid syntax: table_row [item] in [collection] cols=3"
+      table_row_invalid_attribute: "Invalid attribute '%{attribute}' in tablerow loop. Valid attributes are cols, limit, offset, and range"
       tag_never_closed: "'%{block_name}' tag was never closed"
       tag_termination: "Tag '%{token}' was not properly terminated with regexp: %{tag_end}"
       unexpected_else: "%{block_name} tag does not expect 'else' tag"

lib/liquid/parse_context.rb

@@ -3,14 +3,13 @@
 module Liquid
   class ParseContext
     attr_accessor :locale, :line_number, :trim_whitespace, :depth
-    attr_reader :partial, :warnings, :error_mode, :environment
+    attr_reader :partial, :environment
 
     def initialize(options = Const::EMPTY_HASH)
       @environment = options.fetch(:environment, Environment.default)
       @template_options = options ? options.dup : {}
 
-      @locale   = @template_options[:locale] ||= I18n.new
-      @warnings = []
+      @locale = @template_options[:locale] ||= I18n.new
 
       # constructing new StringScanner in Lexer, Tokenizer, etc is expensive
       # This StringScanner will be shared by all of them
@@ -38,7 +37,7 @@ module Liquid
 
     def new_parser(input)
       @string_scanner.string = input
-      Parser.new(@string_scanner)
+      Parser.new(@string_scanner, @expression_cache)
     end
 
     def new_tokenizer(source, start_line_number: nil, for_liquid_tag: false)
@@ -50,15 +49,9 @@ module Liquid
       )
     end
 
-    def parse_expression(markup)
-      Expression.parse(markup, @string_scanner, @expression_cache)
-    end
-
     def partial=(value)
       @partial = value
       @options = value ? partial_options : @template_options
-
-      @error_mode = @options[:error_mode] || @environment.error_mode
     end
 
     def partial_options

lib/liquid/parser.rb

@@ -2,9 +2,10 @@
 
 module Liquid
   class Parser
-    def initialize(input)
-      ss = input.is_a?(StringScanner) ? input : StringScanner.new(input)
-      @tokens = Lexer.tokenize(ss)
+    def initialize(input, expression_cache = nil)
+      @ss = input.is_a?(StringScanner) ? input : StringScanner.new(input)
+      @cache = expression_cache
+      @tokens = Lexer.tokenize(@ss)
       @p      = 0 # pointer to current location
     end
 
@@ -47,23 +48,75 @@ module Liquid
     end
 
     def expression
+      token = @tokens[@p]
+      case token[0]
+      when :id
+        variable_lookup
+      when :open_square
+        unnamed_variable_lookup
+      when :string
+        string
+      when :number
+        number
+      when :open_round
+        range_lookup
+      else
+        raise SyntaxError, "#{token} is not a valid expression"
+      end
+    end
+
+    def number
+      num = consume(:number)
+      Expression.parse_number(num)
+    end
+
+    def string
+      consume(:string)[1..-2]
+    end
+
+    def variable_lookup
+      name = consume(:id)
+      lookups, command_flags = variable_lookups
+      if Expression::LITERALS.key?(name) && lookups.empty?
+        Expression::LITERALS[name]
+      else
+        VariableLookup.new(name, lookups, command_flags)
+      end
+    end
+
+    def unnamed_variable_lookup
+      name = indexed_lookup
+      lookups, command_flags = variable_lookups
+      VariableLookup.new(name, lookups, command_flags)
+    end
+
+    def range_lookup
+      consume(:open_round)
+      first = expression
+      consume(:dotdot)
+      last = expression
+      consume(:close_round)
+      RangeLookup.create(first, last)
+    end
+
+    def expression_string
       token = @tokens[@p]
       case token[0]
       when :id
         str = consume
-        str << variable_lookups
+        str << variable_lookups_string
       when :open_square
         str = consume.dup
-        str << expression
+        str << expression_string
         str << consume(:close_square)
-        str << variable_lookups
+        str << variable_lookups_string
       when :string, :number
         consume
       when :open_round
         consume
-        first = expression
+        first = expression_string
         consume(:dotdot)
-        last = expression
+        last = expression_string
         consume(:close_round)
         "(#{first}..#{last})"
       else
@@ -71,23 +124,23 @@ module Liquid
       end
     end
 
-    def argument
+    def argument_string
       str = +""
       # might be a keyword argument (identifier: expression)
       if look(:id) && look(:colon, 1)
         str << consume << consume << ' '
       end
 
-      str << expression
+      str << expression_string
       str
     end
 
-    def variable_lookups
+    def variable_lookups_string
       str = +""
       loop do
         if look(:open_square)
           str << consume
-          str << expression
+          str << expression_string
           str << consume(:close_square)
         elsif look(:dot)
           str << consume
@@ -98,5 +151,43 @@ module Liquid
       end
       str
     end
+
+    # Assumes safe input. For cases where you need the string.
+    # Don't use this unless you're sure about what you're doing.
+    def unsafe_parse_expression(markup)
+      parse_expression(markup)
+    end
+
+    private
+
+    def parse_expression(markup)
+      Expression.parse(markup, @ss, @cache)
+    end
+
+    def variable_lookups
+      lookups = []
+      command_flags = 0
+      i = -1
+      loop do
+        i += 1
+        if look(:open_square)
+          lookups << indexed_lookup
+        elsif consume?(:dot)
+          lookup = consume(:id)
+          lookups << lookup
+          command_flags |= 1 << i if VariableLookup::COMMAND_METHODS.include?(lookup)
+        else
+          break
+        end
+      end
+      [lookups, command_flags]
+    end
+
+    def indexed_lookup
+      consume(:open_square)
+      expr = expression
+      consume(:close_square)
+      expr
+    end
   end
 end

lib/liquid/parser_switching.rb

@@ -2,42 +2,16 @@
 
 module Liquid
   module ParserSwitching
-    def strict_parse_with_error_mode_fallback(markup)
-      strict_parse_with_error_context(markup)
-    rescue SyntaxError => e
-      case parse_context.error_mode
-      when :strict
-        raise
-      when :warn
-        parse_context.warnings << e
-      end
-      lax_parse(markup)
-    end
-
     def parse_with_selected_parser(markup)
-      case parse_context.error_mode
-      when :strict then strict_parse_with_error_context(markup)
-      when :lax    then lax_parse(markup)
-      when :warn
-        begin
-          strict_parse_with_error_context(markup)
-        rescue SyntaxError => e
-          parse_context.warnings << e
-          lax_parse(markup)
-        end
-      end
-    end
-
-    private
-
-    def strict_parse_with_error_context(markup)
-      strict_parse(markup)
+      parse_markup(markup)
     rescue SyntaxError => e
       e.line_number    = line_number
       e.markup_context = markup_context(markup)
       raise e
     end
 
+    private
+
     def markup_context(markup)
       "in \"#{markup.strip}\""
     end

lib/liquid/partial_cache.rb

@@ -4,7 +4,7 @@ module Liquid
   class PartialCache
     def self.load(template_name, context:, parse_context:)
       cached_partials = context.registers[:cached_partials]
-      cache_key = "#{template_name}:#{parse_context.error_mode}"
+      cache_key = template_name.to_s
       cached = cached_partials[cache_key]
       return cached if cached
 

lib/liquid/range_lookup.rb

@@ -2,15 +2,15 @@
 
 module Liquid
   class RangeLookup
-    def self.parse(start_markup, end_markup, string_scanner, cache = nil)
-      start_obj = Expression.parse(start_markup, string_scanner, cache)
-      end_obj   = Expression.parse(end_markup, string_scanner, cache)
+    def self.create(start_obj, end_obj, start_markup = nil, end_markup = nil)
       if start_obj.respond_to?(:evaluate) || end_obj.respond_to?(:evaluate)
         new(start_obj, end_obj)
       else
         begin
           start_obj.to_i..end_obj.to_i
         rescue NoMethodError
+          start_markup = start_obj.to_s unless start_markup
+          end_markup = end_obj.to_s unless end_markup
           invalid_expr = start_markup unless start_obj.respond_to?(:to_i)
           invalid_expr ||= end_markup unless end_obj.respond_to?(:to_i)
           if invalid_expr

lib/liquid/standardfilters.rb

@@ -3,7 +3,6 @@
 require 'cgi'
 require 'base64'
 require 'bigdecimal'
-
 module Liquid
   module StandardFilters
     MAX_I32 = (1 << 31) - 1
@@ -387,7 +386,7 @@ module Liquid
         end
       elsif ary.all? { |el| el.respond_to?(:[]) }
         begin
-          ary.sort { |a, b| nil_safe_compare(fetch_property(a, property), fetch_property(b, property)) }
+          ary.sort { |a, b| nil_safe_compare(a[property], b[property]) }
         rescue TypeError
           raise_property_error(property)
         end
@@ -416,7 +415,7 @@ module Liquid
         end
       elsif ary.all? { |el| el.respond_to?(:[]) }
         begin
-          ary.sort { |a, b| nil_safe_casecmp(fetch_property(a, property), fetch_property(b, property)) }
+          ary.sort { |a, b| nil_safe_casecmp(a[property], b[property]) }
         rescue TypeError
           raise_property_error(property)
         end
@@ -456,10 +455,10 @@ module Liquid
     #   Tests if any item in an array has a specific property value.
     # @liquid_description
     #   This requires you to provide both the property name and the associated value.
-    # @liquid_syntax array | some: string, string
+    # @liquid_syntax array | has: string, string
     # @liquid_return [boolean]
     def has(input, property, target_value = nil)
-      filter_array(input, property, target_value) { |ary, &block| ary.any?(&block) }
+      filter_array(input, property, target_value, false) { |ary, &block| ary.any?(&block) }
     end
 
     # @liquid_public_docs
@@ -472,7 +471,7 @@ module Liquid
     # @liquid_syntax array | find: string, string
     # @liquid_return [untyped]
     def find(input, property, target_value = nil)
-      filter_array(input, property, target_value) { |ary, &block| ary.find(&block) }
+      filter_array(input, property, target_value, nil) { |ary, &block| ary.find(&block) }
     end
 
     # @liquid_public_docs
@@ -485,7 +484,7 @@ module Liquid
     # @liquid_syntax array | find_index: string, string
     # @liquid_return [number]
     def find_index(input, property, target_value = nil)
-      filter_array(input, property, target_value) { |ary, &block| ary.find_index(&block) }
+      filter_array(input, property, target_value, nil) { |ary, &block| ary.find_index(&block) }
     end
 
     # @liquid_public_docs
@@ -504,7 +503,7 @@ module Liquid
         []
       else
         ary.uniq do |item|
-          fetch_property(item, property)
+          item[property]
         rescue TypeError
           raise_property_error(property)
         rescue NoMethodError
@@ -540,7 +539,7 @@ module Liquid
         if property == "to_liquid"
           e
         elsif e.respond_to?(:[])
-          r = fetch_property(e, property)
+          r = e[property]
           r.is_a?(Proc) ? r.call : r
         end
       end
@@ -564,7 +563,7 @@ module Liquid
         []
       else
         ary.reject do |item|
-          fetch_property(item, property).nil?
+          item[property].nil?
         rescue TypeError
           raise_property_error(property)
         rescue NoMethodError
@@ -712,7 +711,16 @@ module Liquid
       input.gsub(/\r?\n/, "<br />\n")
     end
 
-    # Reformat a date using Ruby's core Time#strftime( string ) -> string
+    # @liquid_public_docs
+    # @liquid_type filter
+    # @liquid_category date
+    # @liquid_summary
+    #   Formats a date according to a specified format string.
+    # @liquid_description
+    #   This filter formats a date using various format specifiers. If the format string is empty,
+    #   the original input is returned. If the input cannot be converted to a date, the original input is returned.
+    #
+    #   The following format specifiers can be used:
     #
     #   %a - The abbreviated weekday name (``Sun'')
     #   %A - The  full  weekday  name (``Sunday'')
@@ -741,8 +749,8 @@ module Liquid
     #   %Y - Year with century
     #   %Z - Time zone name
     #   %% - Literal ``%'' character
-    #
-    #   See also: http://www.ruby-doc.org/core/Time.html#method-i-strftime
+    # @liquid_syntax date | date: string
+    # @liquid_return [string]
     def date(input, format)
       str_format = Utils.to_s(format)
       return input if str_format.empty?
@@ -760,6 +768,8 @@ module Liquid
     # @liquid_syntax array | first
     # @liquid_return [untyped]
     def first(array)
+      # ActiveSupport returns "" for empty strings, not nil
+      return array[0] || "" if array.is_a?(String)
       array.first if array.respond_to?(:first)
     end
 
@@ -771,6 +781,8 @@ module Liquid
     # @liquid_syntax array | last
     # @liquid_return [untyped]
     def last(array)
+      # ActiveSupport returns "" for empty strings, not nil
+      return array[-1] || "" if array.is_a?(String)
       array.last if array.respond_to?(:last)
     end
 
@@ -950,7 +962,7 @@ module Liquid
         if property.nil?
           item
         elsif item.respond_to?(:[])
-          fetch_property(item, property)
+          item[property]
         else
           0
         end
@@ -969,16 +981,16 @@ module Liquid
 
     attr_reader :context
 
-    def filter_array(input, property, target_value, &block)
+    def filter_array(input, property, target_value, default_value = [], &block)
       ary = InputIterator.new(input, context)
 
-      return [] if ary.empty?
+      return default_value if ary.empty?
 
       block.call(ary) do |item|
         if target_value.nil?
-          fetch_property(item, property)
+          item[property]
         else
-          fetch_property(item, property) == target_value
+          item[property] == target_value
         end
       rescue TypeError
         raise_property_error(property)
@@ -988,33 +1000,8 @@ module Liquid
       end
     end
 
-    def fetch_property(drop, property_or_keys)
-      ##
-      # This keeps backward compatibility by supporting properties containing
-      # dots. This is valid in Liquid syntax and used in some runtimes, such as
-      # Shopify with metafields.
-      #
-      # Using this approach, properties like 'price.value' can be accessed in
-      # both of the following examples:
-      #
-      # ```
-      # [
-      #   { 'name' => 'Item 1', 'price.price' => 40000 },
-      #   { 'name' => 'Item 2', 'price' => { 'value' => 39900 } }
-      # ]
-      # ```
-      value = drop[property_or_keys]
-
-      return value if !value.nil? || !property_or_keys.is_a?(String)
-
-      keys = property_or_keys.split('.')
-      keys.reduce(drop) do |drop, key|
-        drop.respond_to?(:[]) ? drop[key] : drop
-      end
-    end
-
     def raise_property_error(property)
-      raise Liquid::ArgumentError, "cannot select the property '#{property}'"
+      raise Liquid::ArgumentError, "cannot select the property '#{Utils.to_s(property)}'"
     end
 
     def apply_operation(input, operand, operation)
@@ -1086,7 +1073,10 @@ module Liquid
       end
 
       def uniq(&block)
-        to_a.uniq(&block)
+        to_a.uniq do |item|
+          item = Utils.to_liquid_value(item)
+          block ? yield(item) : item
+        end
       end
 
       def compact

lib/liquid/tag.rb

@@ -65,11 +65,5 @@ module Liquid
     def blank?
       false
     end
-
-    private
-
-    def parse_expression(markup)
-      parse_context.parse_expression(markup)
-    end
   end
 end

lib/liquid/tags.rb

@@ -19,6 +19,7 @@ require_relative "tags/comment"
 require_relative "tags/raw"
 require_relative "tags/render"
 require_relative "tags/cycle"
+require_relative "tags/doc"
 
 module Liquid
   module Tags
@@ -42,6 +43,7 @@ module Liquid
       'if' => If,
       'echo' => Echo,
       'tablerow' => TableRow,
+      'doc' => Doc,
     }.freeze
   end
 end

lib/liquid/tags/assign.rb

@@ -9,6 +9,10 @@ module Liquid
   #   Creates a new variable.
   # @liquid_description
   #   You can create variables of any [basic type](/docs/api/liquid/basics#types), [object](/docs/api/liquid/objects), or object property.
+  #
+  #   > Caution:
+  #   > Predefined Liquid objects can be overridden by variables with the same name.
+  #   > To make sure that you can access all Liquid objects, make sure that your variable name doesn't match a predefined object's name.
   # @liquid_syntax
   #   {% assign variable_name = value %}
   # @liquid_syntax_keyword variable_name The name of the variable being created.

lib/liquid/tags/capture.rb

@@ -9,6 +9,10 @@ module Liquid
   #   Creates a new variable with a string value.
   # @liquid_description
   #   You can create complex strings with Liquid logic and variables.
+  #
+  #   > Caution:
+  #   > Predefined Liquid objects can be overridden by variables with the same name.
+  #   > To make sure that you can access all Liquid objects, make sure that your variable name doesn't match a predefined object's name.
   # @liquid_syntax
   #   {% capture variable %}
   #     value

lib/liquid/tags/case.rb

@@ -23,20 +23,12 @@ module Liquid
   # @liquid_syntax_keyword second_expression An expression to be rendered when the variable's value matches `second_value`.
   # @liquid_syntax_keyword third_expression An expression to be rendered when the variable's value has no match.
   class Case < Block
-    Syntax     = /(#{QuotedFragment})/o
-    WhenSyntax = /(#{QuotedFragment})(?:(?:\s+or\s+|\s*\,\s*)(#{QuotedFragment}.*))?/om
-
     attr_reader :blocks, :left
 
     def initialize(tag_name, markup, options)
       super
       @blocks = []
-
-      if markup =~ Syntax
-        @left = parse_expression(Regexp.last_match(1))
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.case")
-      end
+      parse_with_selected_parser(markup)
     end
 
     def parse(tokens)
@@ -91,20 +83,31 @@ module Liquid
 
     private
 
+    def parse_markup(markup)
+      parser = @parse_context.new_parser(markup)
+      @left = parser.expression
+      parser.consume(:end_of_string)
+    end
+
     def record_when_condition(markup)
       body = new_body
 
-      while markup
-        unless markup =~ WhenSyntax
-          raise SyntaxError, options[:locale].t("errors.syntax.case_invalid_when")
-        end
+      parse_when(markup, body)
+    end
 
-        markup = Regexp.last_match(2)
+    def parse_when(markup, body)
+      parser = @parse_context.new_parser(markup)
 
-        block = Condition.new(@left, '==', Condition.parse_expression(parse_context, Regexp.last_match(1)))
+      loop do
+        expr = Condition.parse_expression(parser)
+        block = Condition.new(@left, '==', expr)
         block.attach(body)
         @blocks << block
+
+        break unless parser.id?('or') || parser.consume?(:comma)
       end
+
+      parser.consume(:end_of_string)
     end
 
     def record_else_condition(markup)

lib/liquid/tags/cycle.rb

@@ -15,25 +15,13 @@ module Liquid
   # @liquid_syntax
   #   {% cycle string, string, ... %}
   class Cycle < Tag
-    SimpleSyntax = /\A#{QuotedFragment}+/o
-    NamedSyntax  = /\A(#{QuotedFragment})\s*\:\s*(.*)/om
+    UNNAMED_CYCLE_PATTERN = /\w+:0x\h{8}/
 
     attr_reader :variables
 
     def initialize(tag_name, markup, options)
       super
-      case markup
-      when NamedSyntax
-        @variables = variables_from_string(Regexp.last_match(2))
-        @name      = parse_expression(Regexp.last_match(1))
-        @is_named = true
-      when SimpleSyntax
-        @variables = variables_from_string(markup)
-        @name      = @variables.to_s
-        @is_named = !@name.match?(/\w+:0x\h{8}/)
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.cycle")
-      end
+      parse_with_selected_parser(markup)
     end
 
     def named?
@@ -65,17 +53,51 @@ module Liquid
 
     private
 
-    def variables_from_string(markup)
-      markup.split(',').collect do |var|
-        var =~ /\s*(#{QuotedFragment})\s*/o
-        next unless Regexp.last_match(1)
+    # cycle [name:] expression(, expression)*
+    def parse_markup(markup)
+      p = @parse_context.new_parser(markup)
 
-        # Expression Parser returns cached objects, and we need to dup them to
-        # start the cycle over for each new cycle call.
-        # Liquid-C does not have a cache, so we don't need to dup the object.
-        var = parse_expression(Regexp.last_match(1))
-        var.is_a?(VariableLookup) ? var.dup : var
-      end.compact
+      @variables = []
+
+      raise SyntaxError, options[:locale].t("errors.syntax.cycle") if p.look(:end_of_string)
+
+      first_expression = p.expression
+      if p.look(:colon)
+        # cycle name: expr1, expr2, ...
+        @name = first_expression
+        @is_named = true
+        p.consume(:colon)
+        # After the colon, parse the first variable (required for named cycles)
+        @variables << maybe_dup_lookup(p.expression)
+      else
+        # cycle expr1, expr2, ...
+        @variables << maybe_dup_lookup(first_expression)
+      end
+
+      # Parse remaining comma-separated expressions
+      while p.consume?(:comma)
+        break if p.look(:end_of_string)
+
+        @variables << maybe_dup_lookup(p.expression)
+      end
+
+      p.consume(:end_of_string)
+
+      unless @is_named
+        @name = @variables.to_s
+        @is_named = !@name.match?(UNNAMED_CYCLE_PATTERN)
+      end
+    end
+
+    # For backwards compatibility, whenever a lookup is used in an unnamed cycle,
+    # we make it so that the @variables.to_s produces different strings for cycles
+    # called with the same arguments (since @variables.to_s is used as the cycle counter key)
+    # This makes it so {% cycle a, b %} and {% cycle a, b %} have independent counters even if a and b share value.
+    # This is not true for literal values, {% cycle "a", "b" %} and {% cycle "a", "b" %} share the same counter.
+    # I was really scratching my head about this one, but migrating away from this would be more headache
+    # than it's worth. So we're keeping this quirk for now.
+    def maybe_dup_lookup(var)
+      var.is_a?(VariableLookup) ? var.dup : var
     end
 
     class ParseTreeVisitor < Liquid::ParseTreeVisitor

lib/liquid/tags/decrement.rb

@@ -7,10 +7,14 @@ module Liquid
   # @liquid_name decrement
   # @liquid_summary
   #   Creates a new variable, with a default value of -1, that's decreased by 1 with each subsequent call.
+  #
+  #   > Caution:
+  #   > Predefined Liquid objects can be overridden by variables with the same name.
+  #   > To make sure that you can access all Liquid objects, make sure that your variable name doesn't match a predefined object's name.
   # @liquid_description
   #   Variables that are declared with `decrement` are unique to the [layout](/themes/architecture/layouts), [template](/themes/architecture/templates),
   #   or [section](/themes/architecture/sections) file that they're created in. However, the variable is shared across
-  #   [snippets](/themes/architecture#snippets) included in the file.
+  #   [snippets](/themes/architecture/snippets) included in the file.
   #
   #   Similarly, variables that are created with `decrement` are independent from those created with [`assign`](/docs/api/liquid/tags/assign)
   #   and [`capture`](/docs/api/liquid/tags/capture). However, `decrement` and [`increment`](/docs/api/liquid/tags/increment) share

lib/liquid/tags/doc.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module Liquid
+  # @liquid_public_docs
+  # @liquid_type tag
+  # @liquid_category syntax
+  # @liquid_name doc
+  # @liquid_summary
+  #   Documents template elements with annotations.
+  # @liquid_description
+  #   The `doc` tag allows developers to include documentation within Liquid
+  #   templates. Any content inside `doc` tags is not rendered or outputted.
+  #   Liquid code inside will be parsed but not executed. This facilitates
+  #   tooling support for features like code completion, linting, and inline
+  #   documentation.
+  #
+  #   For detailed documentation syntax and examples, see the
+  #   [`LiquidDoc` reference](/docs/storefronts/themes/tools/liquid-doc).
+  #
+  # @liquid_syntax
+  #   {% doc %}
+  #     Renders a message.
+  #
+  #     @param {string} foo - A string value.
+  #     @param {string} [bar] - An optional string value.
+  #
+  #     @example
+  #     {% render 'message', foo: 'Hello', bar: 'World' %}
+  #   {% enddoc %}
+  class Doc < Block
+    NO_UNEXPECTED_ARGS = /\A\s*\z/
+
+    def initialize(tag_name, markup, parse_context)
+      super
+      ensure_valid_markup(tag_name, markup, parse_context)
+    end
+
+    def parse(tokens)
+      @body = +""
+
+      while (token = tokens.shift)
+        tag_name = token =~ BlockBody::FullTokenPossiblyInvalid && Regexp.last_match(2)
+
+        raise_nested_doc_error if tag_name == @tag_name
+
+        if tag_name == block_delimiter
+          parse_context.trim_whitespace = (token[-3] == WhitespaceControl)
+          @body << Regexp.last_match(1) if Regexp.last_match(1) != ""
+          return
+        end
+        @body << token unless token.empty?
+      end
+
+      raise_tag_never_closed(block_name)
+    end
+
+    def render_to_output_buffer(_context, output)
+      output
+    end
+
+    def blank?
+      @body.empty?
+    end
+
+    def nodelist
+      [@body]
+    end
+
+    private
+
+    def ensure_valid_markup(tag_name, markup, parse_context)
+      unless NO_UNEXPECTED_ARGS.match?(markup)
+        raise SyntaxError, parse_context.locale.t("errors.syntax.block_tag_unexpected_args", tag: tag_name)
+      end
+    end
+
+    def raise_nested_doc_error
+      raise SyntaxError, parse_context.locale.t("errors.syntax.doc_invalid_nested")
+    end
+  end
+end

lib/liquid/tags/for.rb

@@ -20,13 +20,11 @@ module Liquid
   # @liquid_syntax_keyword variable The current item in the array.
   # @liquid_syntax_keyword array The array to iterate over.
   # @liquid_syntax_keyword expression The expression to render for each iteration.
-  # @liquid_optional_param limit [number] The number of iterations to perform.
-  # @liquid_optional_param offset [number] The 1-based index to start iterating at.
+  # @liquid_optional_param limit: [number] The number of iterations to perform.
+  # @liquid_optional_param offset: [number] The 1-based index to start iterating at.
   # @liquid_optional_param range [untyped] A custom numeric range to iterate over.
   # @liquid_optional_param reversed [untyped] Iterate in reverse order.
   class For < Block
-    Syntax = /\A(#{VariableSegment}+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/o
-
     attr_reader :collection_name, :variable_name, :limit, :from
 
     def initialize(tag_name, markup, options)
@@ -72,28 +70,13 @@ module Liquid
 
     protected
 
-    def lax_parse(markup)
-      if markup =~ Syntax
-        @variable_name   = Regexp.last_match(1)
-        collection_name  = Regexp.last_match(2)
-        @reversed        = !!Regexp.last_match(3)
-        @name            = "#{@variable_name}-#{collection_name}"
-        @collection_name = parse_expression(collection_name)
-        markup.scan(TagAttributes) do |key, value|
-          set_attribute(key, value)
-        end
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.for")
-      end
-    end
-
-    def strict_parse(markup)
+    def parse_markup(markup)
       p = @parse_context.new_parser(markup)
       @variable_name = p.consume(:id)
       raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_in") unless p.id?('in')
 
-      collection_name  = p.expression
-      @collection_name = parse_expression(collection_name)
+      collection_name  = p.expression_string
+      @collection_name = p.unsafe_parse_expression(collection_name)
 
       @name     = "#{@variable_name}-#{collection_name}"
       @reversed = p.id?('reversed')
@@ -104,7 +87,7 @@ module Liquid
           raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_attribute")
         end
         p.consume(:colon)
-        set_attribute(attribute, p.expression)
+        set_attribute(attribute, p)
       end
       p.consume(:end_of_string)
     end
@@ -174,16 +157,17 @@ module Liquid
       output
     end
 
-    def set_attribute(key, expr)
+    def set_attribute(key, p)
+      expr = p.expression_string
       case key
       when 'offset'
         @from = if expr == 'continue'
           :continue
         else
-          parse_expression(expr)
+          p.unsafe_parse_expression(expr)
         end
       when 'limit'
-        @limit = parse_expression(expr)
+        @limit = p.unsafe_parse_expression(expr)
       end
     end
 

lib/liquid/tags/if.rb

@@ -14,10 +14,6 @@ module Liquid
   # @liquid_syntax_keyword condition The condition to evaluate.
   # @liquid_syntax_keyword expression The expression to render if the condition is met.
   class If < Block
-    Syntax                  = /(#{QuotedFragment})\s*([=!<>a-z_]+)?\s*(#{QuotedFragment})?/o
-    ExpressionsAndOperators = /(?:\b(?:\s?and\s?|\s?or\s?)\b|(?:\s*(?!\b(?:\s?and\s?|\s?or\s?)\b)(?:#{QuotedFragment}|\S+)\s*)+)/o
-    BOOLEAN_OPERATORS       = %w(and or).freeze
-
     attr_reader :blocks
 
     def initialize(tag_name, markup, options)
@@ -77,31 +73,11 @@ module Liquid
       block.attach(new_body)
     end
 
-    def parse_expression(markup)
-      Condition.parse_expression(parse_context, markup)
+    def parse_expression(parser)
+      Condition.parse_expression(parser)
     end
 
-    def lax_parse(markup)
-      expressions = markup.scan(ExpressionsAndOperators)
-      raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop =~ Syntax
-
-      condition = Condition.new(parse_expression(Regexp.last_match(1)), Regexp.last_match(2), parse_expression(Regexp.last_match(3)))
-
-      until expressions.empty?
-        operator = expressions.pop.to_s.strip
-
-        raise SyntaxError, options[:locale].t("errors.syntax.if") unless expressions.pop.to_s =~ Syntax
-
-        new_condition = Condition.new(parse_expression(Regexp.last_match(1)), Regexp.last_match(2), parse_expression(Regexp.last_match(3)))
-        raise SyntaxError, options[:locale].t("errors.syntax.if") unless BOOLEAN_OPERATORS.include?(operator)
-        new_condition.send(operator, condition)
-        condition = new_condition
-      end
-
-      condition
-    end
-
-    def strict_parse(markup)
+    def parse_markup(markup)
       p = @parse_context.new_parser(markup)
       condition = parse_binary_comparisons(p)
       p.consume(:end_of_string)
@@ -120,9 +96,9 @@ module Liquid
     end
 
     def parse_comparison(p)
-      a = parse_expression(p.expression)
+      a = parse_expression(p)
       if (op = p.consume?(:comparison))
-        b = parse_expression(p.expression)
+        b = parse_expression(p)
         Condition.new(a, op, b)
       else
         Condition.new(a)

lib/liquid/tags/include.rb

@@ -6,7 +6,7 @@ module Liquid
   # @liquid_category theme
   # @liquid_name include
   # @liquid_summary
-  #   Renders a [snippet](/themes/architecture#snippets).
+  #   Renders a [snippet](/themes/architecture/snippets).
   # @liquid_description
   #   Inside the snippet, you can access and alter variables that are [created](/docs/api/liquid/tags/variable-tags) outside of the
   #   snippet.
@@ -20,31 +20,11 @@ module Liquid
   class Include < Tag
     prepend Tag::Disableable
 
-    SYNTAX = /(#{QuotedFragment}+)(\s+(?:with|for)\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
-    Syntax = SYNTAX
-
     attr_reader :template_name_expr, :variable_name_expr, :attributes
 
     def initialize(tag_name, markup, options)
       super
-
-      if markup =~ SYNTAX
-
-        template_name = Regexp.last_match(1)
-        variable_name = Regexp.last_match(3)
-
-        @alias_name         = Regexp.last_match(5)
-        @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
-        @template_name_expr = parse_expression(template_name)
-        @attributes         = {}
-
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = parse_expression(value)
-        end
-
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.include")
-      end
+      parse_with_selected_parser(markup)
     end
 
     def parse(_tokens)
@@ -101,6 +81,26 @@ module Liquid
     alias_method :parse_context, :options
     private :parse_context
 
+    def parse_markup(markup)
+      p = @parse_context.new_parser(markup)
+
+      @template_name_expr = p.expression
+      @variable_name_expr = p.expression if p.id?("for") || p.id?("with")
+      @alias_name         = p.consume(:id) if p.id?("as")
+
+      p.consume?(:comma)
+
+      @attributes = {}
+      while p.look(:id)
+        key = p.consume
+        p.consume(:colon)
+        @attributes[key] = p.expression
+        p.consume?(:comma)
+      end
+
+      p.consume(:end_of_string)
+    end
+
     class ParseTreeVisitor < Liquid::ParseTreeVisitor
       def children
         [

lib/liquid/tags/increment.rb

@@ -7,10 +7,14 @@ module Liquid
   # @liquid_name increment
   # @liquid_summary
   #   Creates a new variable, with a default value of 0, that's increased by 1 with each subsequent call.
+  #
+  #   > Caution:
+  #   > Predefined Liquid objects can be overridden by variables with the same name.
+  #   > To make sure that you can access all Liquid objects, make sure that your variable name doesn't match a predefined object's name.
   # @liquid_description
   #   Variables that are declared with `increment` are unique to the [layout](/themes/architecture/layouts), [template](/themes/architecture/templates),
   #   or [section](/themes/architecture/sections) file that they're created in. However, the variable is shared across
-  #   [snippets](/themes/architecture#snippets) included in the file.
+  #   [snippets](/themes/architecture/snippets) included in the file.
   #
   #   Similarly, variables that are created with `increment` are independent from those created with [`assign`](/docs/api/liquid/tags/assign)
   #   and [`capture`](/docs/api/liquid/tags/capture). However, `increment` and [`decrement`](/docs/api/liquid/tags/decrement) share

lib/liquid/tags/render.rb

@@ -6,7 +6,7 @@ module Liquid
   # @liquid_category theme
   # @liquid_name render
   # @liquid_summary
-  #   Renders a [snippet](/themes/architecture#snippets) or [app block](/themes/architecture/sections/section-schema#render-app-blocks).
+  #   Renders a [snippet](/themes/architecture/snippets) or [app block](/themes/architecture/sections/section-schema#render-app-blocks).
   # @liquid_description
   #   Inside snippets and app blocks, you can't directly access variables that are [created](/docs/api/liquid/tags/variable-tags) outside
   #   of the snippet or app block. However, you can [specify variables as parameters](/docs/api/liquid/tags/render#render-passing-variables-to-a-snippet)
@@ -27,7 +27,6 @@ module Liquid
   # @liquid_syntax_keyword filename The name of the snippet to render, without the `.liquid` extension.
   class Render < Tag
     FOR = 'for'
-    SYNTAX = /(#{QuotedString}+)(\s+(with|#{FOR})\s+(#{QuotedFragment}+))?(\s+(?:as)\s+(#{VariableSegment}+))?/o
 
     disable_tags "include"
 
@@ -35,22 +34,7 @@ module Liquid
 
     def initialize(tag_name, markup, options)
       super
-
-      raise SyntaxError, options[:locale].t("errors.syntax.render") unless markup =~ SYNTAX
-
-      template_name = Regexp.last_match(1)
-      with_or_for = Regexp.last_match(3)
-      variable_name = Regexp.last_match(4)
-
-      @alias_name = Regexp.last_match(6)
-      @variable_name_expr = variable_name ? parse_expression(variable_name) : nil
-      @template_name_expr = parse_expression(template_name)
-      @is_for_loop = (with_or_for == FOR)
-
-      @attributes = {}
-      markup.scan(TagAttributes) do |key, value|
-        @attributes[key] = parse_expression(value)
-      end
+      parse_with_selected_parser(markup)
     end
 
     def for_loop?
@@ -99,6 +83,33 @@ module Liquid
       output
     end
 
+    # render (string) (with|for expression)? (as id)? (key: value)*
+    def parse_markup(markup)
+      p = @parse_context.new_parser(markup)
+
+      @template_name_expr = template_name(p)
+      with_or_for         = p.id?("for") || p.id?("with")
+      @variable_name_expr = p.expression if with_or_for
+      @alias_name         = p.consume(:id) if p.id?("as")
+      @is_for_loop        = (with_or_for == FOR)
+
+      p.consume?(:comma)
+
+      @attributes = {}
+      while p.look(:id)
+        key = p.consume
+        p.consume(:colon)
+        @attributes[key] = p.expression
+        p.consume?(:comma)
+      end
+
+      p.consume(:end_of_string)
+    end
+
+    def template_name(p)
+      p.string
+    end
+
     class ParseTreeVisitor < Liquid::ParseTreeVisitor
       def children
         [

lib/liquid/tags/table_row.rb

@@ -19,27 +19,46 @@ module Liquid
   # @liquid_syntax_keyword variable The current item in the array.
   # @liquid_syntax_keyword array The array to iterate over.
   # @liquid_syntax_keyword expression The expression to render.
-  # @liquid_optional_param cols [number] The number of columns that the table should have.
-  # @liquid_optional_param limit [number] The number of iterations to perform.
-  # @liquid_optional_param offset [number] The 1-based index to start iterating at.
+  # @liquid_optional_param cols: [number] The number of columns that the table should have.
+  # @liquid_optional_param limit: [number] The number of iterations to perform.
+  # @liquid_optional_param offset: [number] The 1-based index to start iterating at.
   # @liquid_optional_param range [untyped] A custom numeric range to iterate over.
   class TableRow < Block
-    Syntax = /(\w+)\s+in\s+(#{QuotedFragment}+)/o
+    ALLOWED_ATTRIBUTES = ['cols', 'limit', 'offset', 'range'].freeze
 
     attr_reader :variable_name, :collection_name, :attributes
 
     def initialize(tag_name, markup, options)
       super
-      if markup =~ Syntax
-        @variable_name   = Regexp.last_match(1)
-        @collection_name = parse_expression(Regexp.last_match(2))
-        @attributes      = {}
-        markup.scan(TagAttributes) do |key, value|
-          @attributes[key] = parse_expression(value)
-        end
-      else
-        raise SyntaxError, options[:locale].t("errors.syntax.table_row")
+      parse_with_selected_parser(markup)
+    end
+
+    def parse_markup(markup)
+      p = @parse_context.new_parser(markup)
+
+      @variable_name = p.consume(:id)
+
+      unless p.id?("in")
+        raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_in")
       end
+
+      @collection_name = p.expression
+
+      p.consume?(:comma)
+
+      @attributes = {}
+      while p.look(:id)
+        key = p.consume
+        unless ALLOWED_ATTRIBUTES.include?(key)
+          raise SyntaxError, options[:locale].t("errors.syntax.table_row_invalid_attribute", attribute: key)
+        end
+
+        p.consume(:colon)
+        @attributes[key] = p.expression
+        p.consume?(:comma)
+      end
+
+      p.consume(:end_of_string)
     end
 
     def render_to_output_buffer(context, output)

lib/liquid/template.rb

@@ -2,7 +2,7 @@
 
 module Liquid
   # Templates are central to liquid.
-  # Interpretating templates is a two step process. First you compile the
+  # Interpreting templates is a two step process. First you compile the
   # source code you got. During compile time some extensive error checking is performed.
   # your code should expect to get some SyntaxErrors.
   #
@@ -16,24 +16,11 @@ module Liquid
   #
   class Template
     attr_accessor :root, :name
-    attr_reader :resource_limits, :warnings
+    attr_reader :resource_limits
 
     attr_reader :profiler
 
     class << self
-      # Sets how strict the parser should be.
-      # :lax acts like liquid 2.5 and silently ignores malformed tags in most cases.
-      # :warn is the default and will give deprecation warnings when invalid syntax is used.
-      # :strict will enforce correct syntax.
-      def error_mode=(mode)
-        Deprecations.warn("Template.error_mode=", "Environment#error_mode=")
-        Environment.default.error_mode = mode
-      end
-
-      def error_mode
-        Environment.default.error_mode
-      end
-
       def default_exception_renderer=(renderer)
         Deprecations.warn("Template.default_exception_renderer=", "Environment#exception_renderer=")
         Environment.default.exception_renderer = renderer
@@ -222,7 +209,6 @@ module Liquid
         ParseContext.new(opts)
       end
 
-      @warnings = parse_context.warnings
       parse_context
     end
 

lib/liquid/tokenizer.rb

@@ -103,6 +103,12 @@ module Liquid
 
       pos = @ss.pos -= 2
       @source.byteslice(start, pos - start)
+    rescue ::ArgumentError => e
+      if e.message == "invalid byte sequence in #{@ss.string.encoding}"
+        raise SyntaxError, "Invalid byte sequence in #{@ss.string.encoding}"
+      else
+        raise
+      end
     end
 
     def next_variable_token
@@ -111,7 +117,7 @@ module Liquid
       byte_a = byte_b = @ss.scan_byte
 
       while byte_b
-        byte_a = @ss.scan_byte while byte_a && (byte_a != CLOSE_CURLEY && byte_a != OPEN_CURLEY)
+        byte_a = @ss.scan_byte while byte_a && byte_a != CLOSE_CURLEY && byte_a != OPEN_CURLEY
 
         break unless byte_a
 

lib/liquid/utils.rb

@@ -2,6 +2,9 @@
 
 module Liquid
   module Utils
+    DECIMAL_REGEX = /\A-?\d+\.\d+\z/
+    UNIX_TIMESTAMP_REGEX = /\A\d+\z/
+
     def self.slice_collection(collection, from, to)
       if (from != 0 || !to.nil?) && collection.respond_to?(:load_slice)
         collection.load_slice(from, to)
@@ -52,7 +55,7 @@ module Liquid
       when Numeric
         obj
       when String
-        /\A-?\d+\.\d+\z/.match?(obj.strip) ? BigDecimal(obj) : obj.to_i
+        DECIMAL_REGEX.match?(obj.strip) ? BigDecimal(obj) : obj.to_i
       else
         if obj.respond_to?(:to_number)
           obj.to_number
@@ -66,14 +69,14 @@ module Liquid
       return obj if obj.respond_to?(:strftime)
 
       if obj.is_a?(String)
-        return nil if obj.empty?
+        return if obj.empty?
         obj = obj.downcase
       end
 
       case obj
       when 'now', 'today'
         Time.now
-      when /\A\d+\z/, Integer
+      when UNIX_TIMESTAMP_REGEX, Integer
         Time.at(obj.to_i)
       when String
         Time.parse(obj)
@@ -92,6 +95,8 @@ module Liquid
 
     def self.to_s(obj, seen = {})
       case obj
+      when BigDecimal
+        obj.to_s("F")
       when Hash
         # If the custom hash implementation overrides `#to_s`, use their
         # custom implementation. Otherwise we use Liquid's default

lib/liquid/variable.rb

@@ -30,7 +30,7 @@ module Liquid
       @parse_context = parse_context
       @line_number   = parse_context.line_number
 
-      strict_parse_with_error_mode_fallback(markup)
+      parse_with_selected_parser(markup)
     end
 
     def raw
@@ -41,47 +41,17 @@ module Liquid
       "in \"{{#{markup}}}\""
     end
 
-    def lax_parse(markup)
-      @filters = []
-      return unless markup =~ MarkupWithQuotedFragment
-
-      name_markup   = Regexp.last_match(1)
-      filter_markup = Regexp.last_match(2)
-      @name         = parse_context.parse_expression(name_markup)
-      if filter_markup =~ FilterMarkupRegex
-        filters = Regexp.last_match(1).scan(FilterParser)
-        filters.each do |f|
-          next unless f =~ /\w+/
-          filtername = Regexp.last_match(0)
-          filterargs = f.scan(FilterArgsRegex).flatten
-          @filters << parse_filter_expressions(filtername, filterargs)
-        end
-      end
-    end
-
-    def strict_parse(markup)
+    def parse_markup(markup)
       @filters = []
       p = @parse_context.new_parser(markup)
 
       return if p.look(:end_of_string)
 
-      @name = parse_context.parse_expression(p.expression)
-      while p.consume?(:pipe)
-        filtername = p.consume(:id)
-        filterargs = p.consume?(:colon) ? parse_filterargs(p) : Const::EMPTY_ARRAY
-        @filters << parse_filter_expressions(filtername, filterargs)
-      end
+      @name = p.expression
+      @filters << parse_filter_expressions(p) while p.consume?(:pipe)
       p.consume(:end_of_string)
     end
 
-    def parse_filterargs(p)
-      # first argument
-      filterargs = [p.argument]
-      # followed by comma separated others
-      filterargs << p.argument while p.consume?(:comma)
-      filterargs
-    end
-
     def render(context)
       obj = context.evaluate(@name)
 
@@ -122,22 +92,46 @@ module Liquid
 
     private
 
-    def parse_filter_expressions(filter_name, unparsed_args)
-      filter_args  = []
-      keyword_args = nil
-      unparsed_args.each do |a|
-        if (matches = a.match(JustTagAttributes))
-          keyword_args           ||= {}
-          keyword_args[matches[1]] = parse_context.parse_expression(matches[2])
-        else
-          filter_args << parse_context.parse_expression(a)
-        end
+    # Surprisingly, positional and keyword arguments can be mixed.
+    #
+    # filter = filtername [":" filterargs?]
+    # filterargs = argument ("," argument)*
+    # argument = (positional_argument | keyword_argument)
+    # positional_argument = expression
+    # keyword_argument = id ":" expression
+    def parse_filter_expressions(p)
+      filtername = p.consume(:id)
+      filter_args = []
+      keyword_args = {}
+
+      if p.consume?(:colon)
+        # Parse first argument (no leading comma)
+        argument(p, filter_args, keyword_args) unless end_of_arguments?(p)
+
+        # Parse remaining arguments (with leading commas) and optional trailing comma
+        argument(p, filter_args, keyword_args) while p.consume?(:comma) && !end_of_arguments?(p)
       end
-      result = [filter_name, filter_args]
-      result << keyword_args if keyword_args
+
+      result = [filtername, filter_args]
+      result << keyword_args unless keyword_args.empty?
       result
     end
 
+    def argument(p, positional_arguments, keyword_arguments)
+      if p.look(:id) && p.look(:colon, 1)
+        key = p.consume(:id)
+        p.consume(:colon)
+        value = p.expression
+        keyword_arguments[key] = value
+      else
+        positional_arguments << p.expression
+      end
+    end
+
+    def end_of_arguments?(p)
+      p.look(:pipe) || p.look(:end_of_string)
+    end
+
     def evaluate_filter_expressions(context, filter_args, filter_kwargs)
       parsed_args = filter_args.map { |expr| context.evaluate(expr) }
       if filter_kwargs

lib/liquid/variable_lookup.rb

@@ -7,10 +7,6 @@ module Liquid
     attr_reader :name, :lookups
 
     def self.parse(markup, string_scanner = StringScanner.new(""), cache = nil)
-      new(markup, string_scanner, cache)
-    end
-
-    def initialize(markup, string_scanner = StringScanner.new(""), cache = nil)
       lookups = markup.scan(VariableParser)
 
       name = lookups.shift
@@ -21,12 +17,10 @@ module Liquid
           cache,
         )
       end
-      @name = name
 
-      @lookups       = lookups
-      @command_flags = 0
+      command_flags = 0
 
-      @lookups.each_index do |i|
+      lookups.each_index do |i|
         lookup = lookups[i]
         if lookup&.start_with?('[') && lookup&.end_with?(']')
           lookups[i] = Expression.parse(
@@ -35,9 +29,17 @@ module Liquid
             cache,
           )
         elsif COMMAND_METHODS.include?(lookup)
-          @command_flags |= 1 << i
+          command_flags |= 1 << i
         end
       end
+
+      new(name, lookups, command_flags)
+    end
+
+    def initialize(name, lookups, command_flags)
+      @name = name
+      @lookups = lookups
+      @command_flags = command_flags
     end
 
     def lookup_command?(lookup_index)
@@ -70,6 +72,11 @@ module Liquid
         elsif lookup_command?(i) && object.respond_to?(key)
           object = object.send(key).to_liquid
 
+        # Handle string first/last like ActiveSupport does (returns first/last character)
+        # ActiveSupport returns "" for empty strings, not nil
+        elsif lookup_command?(i) && object.is_a?(String) && (key == "first" || key == "last")
+          object = key == "first" ? (object[0] || "") : (object[-1] || "")
+
           # No key was present with the desired value and it wasn't one of the directly supported
           # keywords either. The only thing we got left is to return nil or
           # raise an exception if `strict_variables` option is set to true

lib/liquid/version.rb

@@ -2,5 +2,5 @@
 # frozen_string_literal: true
 
 module Liquid
-  VERSION = "5.6.5"
+  VERSION = "5.11.0"
 end

performance/benchmark.rb

@@ -4,7 +4,6 @@ require 'benchmark/ips'
 require_relative 'theme_runner'
 
 RubyVM::YJIT.enable if defined?(RubyVM::YJIT)
-Liquid::Environment.default.error_mode = ARGV.first.to_sym if ARGV.first
 
 profiler = ThemeRunner.new
 

performance/memory_profile.rb

@@ -53,8 +53,6 @@ class Profiler
   end
 end
 
-Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
-
 runner = ThemeRunner.new
 Profiler.run do |x|
   x.profile('parse') { runner.compile }

performance/profile.rb

@@ -3,7 +3,6 @@
 require 'stackprof'
 require_relative 'theme_runner'
 
-Liquid::Template.error_mode = ARGV.first.to_sym if ARGV.first
 profiler = ThemeRunner.new
 profiler.run
 

performance/unit/expression_benchmark.rb

@@ -6,7 +6,7 @@ require "benchmark/ips"
 
 require 'liquid'
 
-RubyVM::YJIT.enable
+RubyVM::YJIT.enable if defined?(RubyVM::YJIT)
 
 STRING_MARKUPS = [
   "\"foo\"",
@@ -45,22 +45,14 @@ NUMBER_MARKUPS = [
 
 RANGE_MARKUPS = [
   "(1..30)",
-  "(1...30)",
-  "(1..30..5)",
-  "(1.0...30.0)",
-  "(1.........30)",
   "(1..foo)",
   "(foo..30)",
   "(foo..bar)",
-  "(foo...bar...100)",
-  "(foo...bar...100.0)",
 ]
 
 LITERAL_MARKUPS = [
-  nil,
   'nil',
   'null',
-  '',
   'true',
   'false',
   'blank',
@@ -75,20 +67,39 @@ MARKUPS = {
   "range" => RANGE_MARKUPS,
 }
 
-Benchmark.ips do |x|
-  x.config(time: 5, warmup: 5)
+module Liquid
+  Benchmark.ips do |x|
+    x.config(time: 5, warmup: 5)
 
-  MARKUPS.each do |type, markups|
-    x.report("Liquid::Expression#parse: #{type}") do
-      markups.each do |markup|
-        Liquid::Expression.parse(markup)
+    ss = StringScanner.new('')
+
+    MARKUPS.each do |type, markups|
+      x.report("#{type} - Liquid::Expression#parse") do
+        markups.each do |markup|
+          ss.string = markup
+          Expression.parse(markup, ss)
+        end
+      end
+
+      x.report("#{type} - Liquid::Parser#expression") do
+        markups.each do |markup|
+          ss.string = markup
+          Parser.new(ss).expression
+        end
+      end
+
+      x.report("#{type} - Liquid::Expression.parse(Parser#expression_string)") do
+        markups.each do |markup|
+          ss.string = markup
+          Expression.parse(Parser.new(ss).expression_string, ss)
+        end
+      end
+    end
+
+    x.report("Liquid::Expression#parse: all") do
+      MARKUPS.values.flatten.each do |markup|
+        Expression.parse(markup)
       end
     end
   end
-
-  x.report("Liquid::Expression#parse: all") do
-    MARKUPS.values.flatten.each do |markup|
-      Liquid::Expression.parse(markup)
-    end
-  end
 end

performance/unit/lexer_benchmark.rb

@@ -6,7 +6,7 @@ require "benchmark/ips"
 
 require 'liquid'
 
-RubyVM::YJIT.enable
+RubyVM::YJIT.enable if defined?(RubyVM::YJIT)
 
 EXPRESSIONS = [
   "foo[1..2].baz",
@@ -31,11 +31,12 @@ EXPRESSIONS = [
 
 Benchmark.ips do |x|
   x.config(time: 10, warmup: 5)
+  ss = StringScanner.new('')
 
   x.report("Liquid::Lexer#tokenize") do
     EXPRESSIONS.each do |expr|
-      l = Liquid::Lexer.new(expr)
-      l.tokenize
+      ss.string = expr
+      Liquid::Lexer.tokenize(ss)
     end
   end
 

spec/ruby_liquid.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+# Liquid Spec Adapter for Shopify/liquid (Ruby reference implementation)
+#
+# Run with: bundle exec liquid-spec run spec/ruby_liquid.rb
+
+$LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
+require 'liquid'
+
+LiquidSpec.configure do |config|
+  # Run core Liquid specs
+  config.features = [:core]
+end
+
+# Compile a template string into a Liquid::Template
+LiquidSpec.compile do |ctx, source, options|
+  ctx[:template] = Liquid::Template.parse(source, **options)
+end
+
+# Render a compiled template with the given context
+# @param ctx [Hash] adapter context containing :template
+# @param assigns [Hash] environment variables
+# @param options [Hash] :registers, :strict_errors, :exception_renderer
+LiquidSpec.render do |ctx, assigns, options|
+  registers = Liquid::Registers.new(options[:registers] || {})
+
+  context = Liquid::Context.build(
+    static_environments: assigns,
+    registers: registers,
+    rethrow_errors: options[:strict_errors],
+  )
+
+  context.exception_renderer = options[:exception_renderer] if options[:exception_renderer]
+
+  ctx[:template].render(context)
+end

spec/ruby_liquid_with_active_support.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+# Liquid Spec Adapter for Shopify/liquid with ActiveSupport loaded
+#
+# Run with: bundle exec liquid-spec run spec/ruby_liquid_with_active_support.rb
+
+$LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
+require 'active_support/all'
+require 'liquid'
+
+LiquidSpec.configure do |config|
+  # Run core Liquid specs plus ActiveSupport SafeBuffer tests
+  config.features = [:core, :activesupport]
+end
+
+# Compile a template string into a Liquid::Template
+LiquidSpec.compile do |ctx, source, options|
+  ctx[:template] = Liquid::Template.parse(source, **options)
+end
+
+# Render a compiled template with the given context
+# @param ctx [Hash] adapter context containing :template
+# @param assigns [Hash] environment variables
+# @param options [Hash] :registers, :strict_errors, :exception_renderer
+LiquidSpec.render do |ctx, assigns, options|
+  registers = Liquid::Registers.new(options[:registers] || {})
+
+  context = Liquid::Context.build(
+    static_environments: assigns,
+    registers: registers,
+    rethrow_errors: options[:strict_errors],
+  )
+
+  context.exception_renderer = options[:exception_renderer] if options[:exception_renderer]
+
+  ctx[:template].render(context)
+end

spec/ruby_liquid_yjit.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+# Liquid Spec Adapter for Shopify/liquid with YJIT + ActiveSupport
+#
+# Run with: bundle exec liquid-spec run spec/ruby_liquid_yjit.rb
+
+$LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
+
+# Enable YJIT if available
+if defined?(RubyVM::YJIT) && RubyVM::YJIT.respond_to?(:enable)
+  RubyVM::YJIT.enable
+end
+
+require 'active_support/all'
+require 'liquid'
+
+LiquidSpec.configure do |config|
+  config.features = [:core, :activesupport]
+end
+
+# Compile a template string into a Liquid::Template
+LiquidSpec.compile do |ctx, source, options|
+  ctx[:template] = Liquid::Template.parse(source, **options)
+end
+
+# Render a compiled template with the given context
+LiquidSpec.render do |ctx, assigns, options|
+  registers = Liquid::Registers.new(options[:registers] || {})
+
+  context = Liquid::Context.build(
+    static_environments: assigns,
+    registers: registers,
+    rethrow_errors: options[:strict_errors],
+  )
+
+  context.exception_renderer = options[:exception_renderer] if options[:exception_renderer]
+
+  ctx[:template].render(context)
+end

test/integration/assign_test.rb

@@ -39,13 +39,11 @@ class AssignTest < Minitest::Test
     assert_match_syntax_error(/assign/, '{% assign foo not values %}.')
   end
 
-  def test_assign_uses_error_mode
+  def test_assign_throws_on_unsupported_syntax
     assert_match_syntax_error(
-      "Expected dotdot but found pipe in ",
+      "Expected dotdot but found pipe",
       "{% assign foo = ('X' | downcase) %}",
-      error_mode: :strict,
     )
-    assert_template_result("", "{% assign foo = ('X' | downcase) %}", error_mode: :lax)
   end
 
   def test_expression_with_whitespace_in_square_brackets

test/integration/context_test.rb

@@ -632,13 +632,26 @@ class ContextTest < Minitest::Test
   end
 
   def test_has_key_will_not_add_an_error_for_missing_keys
-    with_error_mode(:strict) do
-      context = Context.new
-      context.key?('unknown')
-      assert_empty(context.errors)
+    context = Context.new
+    context.key?('unknown')
+    assert_empty(context.errors)
+  end
+
+  def test_key_lookup_will_raise_for_missing_keys_when_strict_variables_is_enabled
+    context = Context.new
+    context.strict_variables = true
+    assert_raises(Liquid::UndefinedVariable) do
+      context['unknown']
     end
   end
 
+  def test_has_key_will_not_raise_for_missing_keys_when_strict_variables_is_enabled
+    context = Context.new
+    context.strict_variables = true
+    refute(context.key?('unknown'))
+    assert_empty(context.errors)
+  end
+
   def test_context_always_uses_static_registers
     registers = {
       my_register: :my_value,

test/integration/error_handling_test.rb

@@ -67,20 +67,11 @@ class ErrorHandlingTest < Minitest::Test
   end
 
   def test_unrecognized_operator
-    with_error_mode(:strict) do
-      assert_raises(SyntaxError) do
-        Liquid::Template.parse(' {% if 1 =! 2 %}ok{% endif %} ')
-      end
+    assert_raises(SyntaxError) do
+      Liquid::Template.parse(' {% if 1 =! 2 %}ok{% endif %} ')
     end
   end
 
-  def test_lax_unrecognized_operator
-    template = Liquid::Template.parse(' {% if 1 =! 2 %}ok{% endif %} ', error_mode: :lax)
-    assert_equal(' Liquid error: Unknown operator =! ', template.render)
-    assert_equal(1, template.errors.size)
-    assert_equal(Liquid::ArgumentError, template.errors.first.class)
-  end
-
   def test_with_line_numbers_adds_numbers_to_parser_errors
     source = <<~LIQUID
       foobar
@@ -104,25 +95,6 @@ class ErrorHandlingTest < Minitest::Test
     assert_match_syntax_error(/Liquid syntax error \(line 3\)/, source)
   end
 
-  def test_parsing_warn_with_line_numbers_adds_numbers_to_lexer_errors
-    template = Liquid::Template.parse(
-      '
-        foobar
-
-        {% if 1 =! 2 %}ok{% endif %}
-
-        bla
-            ',
-      error_mode: :warn,
-      line_numbers: true,
-    )
-
-    assert_equal(
-      ['Liquid syntax error (line 4): Unexpected character = in "1 =! 2"'],
-      template.warnings.map(&:message),
-    )
-  end
-
   def test_parsing_strict_with_line_numbers_adds_numbers_to_lexer_errors
     err = assert_raises(SyntaxError) do
       Liquid::Template.parse(
@@ -133,7 +105,6 @@ class ErrorHandlingTest < Minitest::Test
 
           bla
                 ',
-        error_mode: :strict,
         line_numbers: true,
       )
     end
@@ -157,34 +128,16 @@ class ErrorHandlingTest < Minitest::Test
 
   def test_strict_error_messages
     err = assert_raises(SyntaxError) do
-      Liquid::Template.parse(' {% if 1 =! 2 %}ok{% endif %} ', error_mode: :strict)
+      Liquid::Template.parse(' {% if 1 =! 2 %}ok{% endif %} ')
     end
     assert_equal('Liquid syntax error: Unexpected character = in "1 =! 2"', err.message)
 
     err = assert_raises(SyntaxError) do
-      Liquid::Template.parse('{{%%%}}', error_mode: :strict)
+      Liquid::Template.parse('{{%%%}}')
     end
     assert_equal('Liquid syntax error: Unexpected character % in "{{%%%}}"', err.message)
   end
 
-  def test_warnings
-    template = Liquid::Template.parse('{% if ~~~ %}{{%%%}}{% else %}{{ hello. }}{% endif %}', error_mode: :warn)
-    assert_equal(3, template.warnings.size)
-    assert_equal('Unexpected character ~ in "~~~"', template.warnings[0].to_s(false))
-    assert_equal('Unexpected character % in "{{%%%}}"', template.warnings[1].to_s(false))
-    assert_equal('Expected id but found end_of_string in "{{ hello. }}"', template.warnings[2].to_s(false))
-    assert_equal('', template.render)
-  end
-
-  def test_warning_line_numbers
-    template = Liquid::Template.parse("{% if ~~~ %}\n{{%%%}}{% else %}\n{{ hello. }}{% endif %}", error_mode: :warn, line_numbers: true)
-    assert_equal('Liquid syntax error (line 1): Unexpected character ~ in "~~~"', template.warnings[0].message)
-    assert_equal('Liquid syntax error (line 2): Unexpected character % in "{{%%%}}"', template.warnings[1].message)
-    assert_equal('Liquid syntax error (line 3): Expected id but found end_of_string in "{{ hello. }}"', template.warnings[2].message)
-    assert_equal(3, template.warnings.size)
-    assert_equal([1, 2, 3], template.warnings.map(&:line_number))
-  end
-
   # Liquid should not catch Exceptions that are not subclasses of StandardError, like Interrupt and NoMemoryError
   def test_exceptions_propagate
     assert_raises(Exception) do

test/integration/expression_test.rb

@@ -26,8 +26,7 @@ class ExpressionTest < Minitest::Test
   def test_float
     assert_template_result("-17.42", "{{ -17.42 }}")
     assert_template_result("2.5", "{{ 2.5 }}")
-    assert_expression_result(0.0, "0.....5")
-    assert_expression_result(0.0, "-0..1")
+
     assert_expression_result(1.5, "1.5")
 
     # this is a unfortunate quirky behavior of Liquid
@@ -47,23 +46,11 @@ class ExpressionTest < Minitest::Test
       "{{ (false..true) }}",
     )
     assert_match_syntax_error(
-      "Liquid syntax error (line 1): Invalid expression type '(1..2)' in range expression",
+      "Liquid syntax error (line 1): Invalid expression type '1..2' in range expression",
       "{{ ((1..2)..3) }}",
     )
   end
 
-  def test_quirky_negative_sign_expression_markup
-    result = Expression.parse("-", nil)
-    assert(result.is_a?(VariableLookup))
-    assert_equal("-", result.name)
-
-    # for this template, the expression markup is "-"
-    assert_template_result(
-      "",
-      "{{ - 'theme.css' - }}",
-    )
-  end
-
   def test_expression_cache
     skip("Liquid-C does not support Expression caching") if defined?(Liquid::C) && Liquid::C.enabled
 
@@ -80,7 +67,7 @@ class ExpressionTest < Minitest::Test
     Liquid::Template.parse(template, expression_cache: cache).render
 
     assert_equal(
-      ["1", "2", "x", "y"],
+      [],
       cache.to_a.map { _1[0] }.sort,
     )
   end
@@ -104,7 +91,7 @@ class ExpressionTest < Minitest::Test
     cache = parse_context.instance_variable_get(:@expression_cache)
 
     assert_equal(
-      ["1", "2", "x", "y"],
+      [],
       cache.to_a.map { _1[0] }.sort,
     )
   end
@@ -125,7 +112,7 @@ class ExpressionTest < Minitest::Test
     Liquid::Template.parse(template, expression_cache: cache).render
 
     assert_equal(
-      ["1", "2", "x", "y"],
+      [],
       cache.to_a.map { _1[0] }.sort,
     )
   end
@@ -147,6 +134,35 @@ class ExpressionTest < Minitest::Test
     assert(parse_context.instance_variable_get(:@expression_cache).nil?)
   end
 
+  def test_parser_expression_with_variable_lookup
+    parse_context = Liquid::ParseContext.new
+    parser = parse_context.new_parser('product.title')
+    result = parser.expression
+
+    assert_instance_of(Liquid::VariableLookup, result)
+    assert_equal('product', result.name)
+    assert_equal(['title'], result.lookups)
+  end
+
+  def test_parser_expression_with_number
+    parse_context = Liquid::ParseContext.new
+    parser = parse_context.new_parser('42')
+    result = parser.expression
+
+    assert_equal(42, result)
+  end
+
+  def test_parser_expression_raises_syntax_error_for_invalid_expression
+    parse_context = Liquid::ParseContext.new
+    parser = parse_context.new_parser('')
+
+    error = assert_raises(Liquid::SyntaxError) do
+      parser.expression
+    end
+
+    assert_match(/is not a valid expression/, error.message)
+  end
+
   private
 
   def assert_expression_result(expect, markup, **assigns)

test/integration/hash_rendering_test.rb

@@ -88,17 +88,11 @@ class HashRenderingTest < Minitest::Test
   end
 
   def test_rendering_hash_with_custom_to_s_method_uses_custom_to_s
-    my_hash = Class.new(Hash) do
-      def to_s
-        "kewl"
-      end
-    end.new
-
-    assert_template_result("kewl", "{{ my_hash }}", { "my_hash" => my_hash })
+    assert_template_result("kewl", "{{ my_hash }}", { "my_hash" => HashWithCustomToS.new })
   end
 
   def test_rendering_hash_without_custom_to_s_uses_default_inspect
-    my_hash = Class.new(Hash).new
+    my_hash = HashWithoutCustomToS.new
     my_hash[:foo] = :bar
 
     assert_template_result("{:foo=>:bar}", "{{ my_hash }}", { "my_hash" => my_hash })

test/integration/parsing_quirks_test.rb

@@ -31,58 +31,25 @@ class ParsingQuirksTest < Minitest::Test
   def test_error_on_empty_filter
     assert(Template.parse("{{test}}"))
 
-    with_error_mode(:lax) do
-      assert(Template.parse("{{|test}}"))
-    end
-
-    with_error_mode(:strict) do
-      assert_raises(SyntaxError) { Template.parse("{{|test}}") }
-      assert_raises(SyntaxError) { Template.parse("{{test |a|b|}}") }
-    end
+    assert_raises(Liquid::SyntaxError) { Template.parse("{{|test}}") }
+    assert_raises(Liquid::SyntaxError) { Template.parse("{{test |a|b|}}") }
   end
 
   def test_meaningless_parens_error
-    with_error_mode(:strict) do
-      assert_raises(SyntaxError) do
-        markup = "a == 'foo' or (b == 'bar' and c == 'baz') or false"
-        Template.parse("{% if #{markup} %} YES {% endif %}")
-      end
+    assert_raises(SyntaxError) do
+      markup = "a == 'foo' or (b == 'bar' and c == 'baz') or false"
+      Template.parse("{% if #{markup} %} YES {% endif %}")
     end
   end
 
   def test_unexpected_characters_syntax_error
-    with_error_mode(:strict) do
-      assert_raises(SyntaxError) do
-        markup = "true && false"
-        Template.parse("{% if #{markup} %} YES {% endif %}")
-      end
-      assert_raises(SyntaxError) do
-        markup = "false || true"
-        Template.parse("{% if #{markup} %} YES {% endif %}")
-      end
-    end
-  end
-
-  def test_no_error_on_lax_empty_filter
-    assert(Template.parse("{{test |a|b|}}", error_mode: :lax))
-    assert(Template.parse("{{test}}", error_mode: :lax))
-    assert(Template.parse("{{|test|}}", error_mode: :lax))
-  end
-
-  def test_meaningless_parens_lax
-    with_error_mode(:lax) do
-      assigns = { 'b' => 'bar', 'c' => 'baz' }
-      markup  = "a == 'foo' or (b == 'bar' and c == 'baz') or false"
-      assert_template_result(' YES ', "{% if #{markup} %} YES {% endif %}", assigns)
-    end
-  end
-
-  def test_unexpected_characters_silently_eat_logic_lax
-    with_error_mode(:lax) do
+    assert_raises(SyntaxError) do
       markup = "true && false"
-      assert_template_result(' YES ', "{% if #{markup} %} YES {% endif %}")
+      Template.parse("{% if #{markup} %} YES {% endif %}")
+    end
+    assert_raises(SyntaxError) do
       markup = "false || true"
-      assert_template_result('', "{% if #{markup} %} YES {% endif %}")
+      Template.parse("{% if #{markup} %} YES {% endif %}")
     end
   end
 
@@ -92,32 +59,6 @@ class ParsingQuirksTest < Minitest::Test
     end
   end
 
-  def test_unanchored_filter_arguments
-    with_error_mode(:lax) do
-      assert_template_result('hi', "{{ 'hi there' | split$$$:' ' | first }}")
-
-      assert_template_result('x', "{{ 'X' | downcase) }}")
-
-      # After the messed up quotes a filter without parameters (reverse) should work
-      # but one with parameters (remove) shouldn't be detected.
-      assert_template_result('here',  "{{ 'hi there' | split:\"t\"\" | reverse | first}}")
-      assert_template_result('hi ', "{{ 'hi there' | split:\"t\"\" | remove:\"i\" | first}}")
-    end
-  end
-
-  def test_invalid_variables_work
-    with_error_mode(:lax) do
-      assert_template_result('bar', "{% assign 123foo = 'bar' %}{{ 123foo }}")
-      assert_template_result('123', "{% assign 123 = 'bar' %}{{ 123 }}")
-    end
-  end
-
-  def test_extra_dots_in_ranges
-    with_error_mode(:lax) do
-      assert_template_result('12345', "{% for i in (1...5) %}{{ i }}{% endfor %}")
-    end
-  end
-
   def test_blank_variable_markup
     assert_template_result('', "{{}}")
   end
@@ -131,24 +72,4 @@ class ParsingQuirksTest < Minitest::Test
   def test_contains_in_id
     assert_template_result(' YES ', '{% if containsallshipments == true %} YES {% endif %}', { 'containsallshipments' => true })
   end
-
-  def test_incomplete_expression
-    with_error_mode(:lax) do
-      assert_template_result("false", "{{ false - }}")
-      assert_template_result("false", "{{ false > }}")
-      assert_template_result("false", "{{ false < }}")
-      assert_template_result("false", "{{ false = }}")
-      assert_template_result("false", "{{ false ! }}")
-      assert_template_result("false", "{{ false 1 }}")
-      assert_template_result("false", "{{ false a }}")
-
-      assert_template_result("false", "{% liquid assign foo = false -\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false >\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false <\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false =\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false !\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false 1\n%}{{ foo }}")
-      assert_template_result("false", "{% liquid assign foo = false a\n%}{{ foo }}")
-    end
-  end
 end # ParsingQuirksTest

test/integration/security_test.rb

@@ -59,7 +59,7 @@ class SecurityTest < Minitest::Test
 
     GC.start
 
-    assert_equal([], (Symbol.all_symbols - current_symbols))
+    assert_equal([], Symbol.all_symbols - current_symbols)
   end
 
   def test_does_not_add_drop_methods_to_symbol_table
@@ -70,7 +70,7 @@ class SecurityTest < Minitest::Test
     assert_equal("", Template.parse("{{ drop.custom_method_2 }}", assigns).render!)
     assert_equal("", Template.parse("{{ drop.custom_method_3 }}", assigns).render!)
 
-    assert_equal([], (Symbol.all_symbols - current_symbols))
+    assert_equal([], Symbol.all_symbols - current_symbols)
   end
 
   def test_max_depth_nested_blocks_does_not_raise_exception

test/integration/standard_filter_test.rb

@@ -54,30 +54,6 @@ class TestEnumerable < Liquid::Drop
   end
 end
 
-class TestDeepEnumerable < Liquid::Drop
-  include Enumerable
-
-  class Product < Liquid::Drop
-    attr_reader :title, :price, :premium
-
-    def initialize(title:, price:, premium: nil)
-      @title = { "content" => title, "language" => "en" }
-      @price = { "value" => price, "unit" => "USD" }
-      @premium = { "category" => premium } if premium
-    end
-  end
-
-  def each(&block)
-    [
-      Product.new(title: "Pro goggles",    price: 1299),
-      Product.new(title: "Thermal gloves", price: 1299),
-      Product.new(title: "Alpine jacket",  price: 3999, premium: 'Basic'),
-      Product.new(title: "Mountain boots", price: 3899, premium: 'Pro'),
-      Product.new(title: "Safety helmet",  price: 1999)
-    ].each(&block)
-  end
-end
-
 class NumberLikeThing < Liquid::Drop
   def initialize(amount)
     @amount = amount
@@ -140,7 +116,7 @@ class StandardFiltersTest < Minitest::Test
   end
 
   def test_slice_on_arrays
-    input = 'foobar'.split(//)
+    input = 'foobar'.split('')
     assert_equal(%w(o o b), @filters.slice(input, 1, 3))
     assert_equal(%w(o o b a r), @filters.slice(input, 1, 1000))
     assert_equal(%w(), @filters.slice(input, 1, 0))
@@ -157,6 +133,18 @@ class StandardFiltersTest < Minitest::Test
     assert_equal([], @filters.slice(input, -(1 << 63), 6))
   end
 
+  def test_find_on_empty_array
+    assert_nil(@filters.find([], 'foo', 'bar'))
+  end
+
+  def test_find_index_on_empty_array
+    assert_nil(@filters.find_index([], 'foo', 'bar'))
+  end
+
+  def test_has_on_empty_array
+    refute(@filters.has([], 'foo', 'bar'))
+  end
+
   def test_truncate
     assert_equal('1234...', @filters.truncate('1234567890', 7))
     assert_equal('1234567890', @filters.truncate('1234567890', 20))
@@ -306,13 +294,7 @@ class StandardFiltersTest < Minitest::Test
   end
 
   def test_join_calls_to_liquid_on_each_element
-    drop = Class.new(Liquid::Drop) do
-      def to_liquid
-        'i did it'
-      end
-    end
-
-    assert_equal('i did it, i did it', @filters.join([drop.new, drop.new], ", "))
+    assert_equal('i did it, i did it', @filters.join([CustomToLiquidDrop.new('i did it'), CustomToLiquidDrop.new('i did it')], ", "))
   end
 
   def test_sort
@@ -426,15 +408,6 @@ class StandardFiltersTest < Minitest::Test
     end
   end
 
-  def test_sort_natural_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | sort_natural: 'title.content' | map: 'title.content' | join: ', ' -}}
-    LIQUID
-    expected_output = "Alpine jacket, Mountain boots, Pro goggles, Safety helmet, Thermal gloves"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_legacy_sort_hash
     assert_equal([{ a: 1, b: 2 }], @filters.sort(a: 1, b: 2))
   end
@@ -471,15 +444,6 @@ class StandardFiltersTest < Minitest::Test
     end
   end
 
-  def test_uniq_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | uniq: 'price.value' | map: "title.content" | join: ', ' -}}
-    LIQUID
-    expected_output = "Pro goggles, Alpine jacket, Mountain boots, Safety helmet"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_compact_empty_array
     assert_equal([], @filters.compact([], "a"))
   end
@@ -496,15 +460,6 @@ class StandardFiltersTest < Minitest::Test
     end
   end
 
-  def test_compact_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | compact: 'premium.category' | map: 'title.content' | join: ', ' -}}
-    LIQUID
-    expected_output = "Alpine jacket, Mountain boots"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_reverse
     assert_equal([4, 3, 2, 1], @filters.reverse([1, 2, 3, 4]))
   end
@@ -599,12 +554,23 @@ class StandardFiltersTest < Minitest::Test
     end
   end
 
-  def test_map_returns_empty_with_no_property
+  def test_map_with_value_property
+    array = [
+      { "handle" => "alpha", "value" => "A" },
+      { "handle" => "beta", "value" => "B" },
+      { "handle" => "gamma", "value" => "C" }
+    ]
+
+    assert_template_result("A B C", "{{ array | map: 'value' | join: ' ' }}", { "array" => array })
+  end
+
+  def test_map_returns_input_with_no_property
     foo = [
       [1],
       [2],
       [3],
     ]
+
     assert_raises(Liquid::ArgumentError) do
       @filters.map(foo, nil)
     end
@@ -614,15 +580,6 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result("213", '{{ foo | sort: "bar" | map: "foo" }}', { "foo" => TestEnumerable.new })
   end
 
-  def test_sort_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | sort: 'price.value' | map: 'title.content' | join: ', ' -}}
-    LIQUID
-    expected_output = "Pro goggles, Thermal gloves, Safety helmet, Mountain boots, Alpine jacket"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_first_and_last_call_to_liquid
     assert_template_result('foobar', '{{ foo | first }}', { 'foo' => [ThingWithToLiquid.new] })
     assert_template_result('foobar', '{{ foo | last }}', { 'foo' => [ThingWithToLiquid.new] })
@@ -670,6 +627,40 @@ class StandardFiltersTest < Minitest::Test
     assert_nil(@filters.last([]))
   end
 
+  def test_first_last_on_strings
+    # Ruby's String class does not have first/last methods by default.
+    # ActiveSupport adds String#first and String#last to return the first/last character.
+    # Liquid must work without ActiveSupport, so the first/last filters handle strings specially.
+    #
+    # This enables template patterns like:
+    #   {{ product.title | first }}  => "S" (for "Snowboard")
+    #   {{ customer.name | last }}   => "h" (for "Smith")
+    #
+    # Note: ActiveSupport returns "" for empty strings, not nil.
+    assert_equal('f', @filters.first('foo'))
+    assert_equal('o', @filters.last('foo'))
+    assert_equal('', @filters.first(''))
+    assert_equal('', @filters.last(''))
+  end
+
+  def test_first_last_on_unicode_strings
+    # Unicode strings should return the first/last grapheme cluster (character),
+    # not the first/last byte. Ruby's String#[] handles this correctly with index 0/-1.
+    # This ensures international text works properly:
+    #   {{ korean_name | first }} => "고" (not a partial byte sequence)
+    assert_equal('고', @filters.first('고스트빈'))
+    assert_equal('빈', @filters.last('고스트빈'))
+  end
+
+  def test_first_last_on_strings_via_template
+    # Integration test to verify the filter works end-to-end in templates.
+    # Empty strings return empty output (nil renders as empty string).
+    assert_template_result('f', '{{ name | first }}', { 'name' => 'foo' })
+    assert_template_result('o', '{{ name | last }}', { 'name' => 'foo' })
+    assert_template_result('', '{{ name | first }}', { 'name' => '' })
+    assert_template_result('', '{{ name | last }}', { 'name' => '' })
+  end
+
   def test_replace
     assert_equal('b b b b', @filters.replace('a a a a', 'a', 'b'))
     assert_equal('2 2 2 2', @filters.replace('1 1 1 1', 1, 2))
@@ -939,15 +930,6 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, template, { "array" => array })
   end
 
-  def test_reject_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | reject: 'title.content', 'Pro goggles' | map: 'price.value' | join: ', ' -}}
-    LIQUID
-    expected_output = "1299, 3999, 3899, 1999"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_has
     array = [
       { "handle" => "alpha", "ok" => true },
@@ -976,6 +958,18 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, "{{ array | has: 'ok', true }}", { "array" => array })
   end
 
+  def test_has_with_empty_arrays
+    template = <<~LIQUID
+      {%- assign has_product = products | has: 'title.content', 'Not found' -%}
+      {%- unless has_product -%}
+        Product not found.
+      {%- endunless -%}
+    LIQUID
+    expected_output = "Product not found."
+
+    assert_template_result(expected_output, template, { "products" => [] })
+  end
+
   def test_has_with_false_value
     array = [
       { "handle" => "alpha", "ok" => true },
@@ -1004,16 +998,6 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, template, { "array" => array })
   end
 
-  def test_has_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | has: 'title.content', 'Pro goggles' -}},
-      {{- products | has: 'title.content', 'foo' -}}
-    LIQUID
-    expected_output = "true,false"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_find_with_value
     products = [
       { "title" => "Pro goggles",    "price" => 1299 },
@@ -1032,14 +1016,16 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, template, { "products" => products })
   end
 
-  def test_find_with_deep_enumerables
+  def test_find_with_empty_arrays
     template = <<~LIQUID
-      {%- assign product = products | find: 'title.content', 'Pro goggles' -%}
-      {{- product.title.content -}}
+      {%- assign product = products | find: 'title.content', 'Not found' -%}
+      {%- unless product -%}
+        Product not found.
+      {%- endunless -%}
     LIQUID
-    expected_output = "Pro goggles"
+    expected_output = "Product not found."
 
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
+    assert_template_result(expected_output, template, { "products" => [] })
   end
 
   def test_find_index_with_value
@@ -1060,14 +1046,16 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, template, { "products" => products })
   end
 
-  def test_find_index_with_deep_enumerables
+  def test_find_index_with_empty_arrays
     template = <<~LIQUID
-      {%- assign index = products | find_index: 'title.content', 'Alpine jacket' -%}
-      {{- index -}}
+      {%- assign index = products | find_index: 'title.content', 'Not found' -%}
+      {%- unless index -%}
+        Index not found.
+      {%- endunless -%}
     LIQUID
-    expected_output = "2"
+    expected_output = "Index not found."
 
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
+    assert_template_result(expected_output, template, { "products" => [] })
   end
 
   def test_where
@@ -1084,6 +1072,23 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result(expected_output, template, { "array" => array })
   end
 
+  def test_where_with_empty_string_is_a_no_op
+    environment = { "array" => ["alpha", "beta", "gamma"] }
+    expected_output = "alpha beta gamma"
+    template = "{{ array | where: '' | join: ' ' }}"
+
+    assert_template_result(expected_output, template, environment)
+  end
+
+  def test_where_with_nil_is_a_no_op
+    environment = { "array" => ["alpha", "beta", "gamma"] }
+    template = "{{ array | where: nil | join: ' ' }}"
+
+    assert_raises(Liquid::ArgumentError) do
+      assert_template_result("alpha beta gamma", template, environment)
+    end
+  end
+
   def test_where_with_value
     array = [
       { "handle" => "alpha", "ok" => true },
@@ -1168,15 +1173,6 @@ class StandardFiltersTest < Minitest::Test
     assert_nil(@filters.where([nil], "ok"))
   end
 
-  def test_where_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | where: 'title.content', 'Pro goggles' | map: 'price.value' -}}
-    LIQUID
-    expected_output = "1299"
-
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
-  end
-
   def test_all_filters_never_raise_non_liquid_exception
     test_drop = TestDrop.new(value: "test")
     test_drop.context = Context.new
@@ -1328,13 +1324,31 @@ class StandardFiltersTest < Minitest::Test
     assert_template_result("0", "{{ input | sum: 'subtotal' }}", { "input" => input })
   end
 
-  def test_sum_with_deep_enumerables
-    template = <<~LIQUID
-      {{- products | sum: 'price.value' -}}
-    LIQUID
-    expected_output = "12495"
+  def test_sum_with_non_string_property
+    input = [{ true => 1 }, { 1.0 => 0.2, 1 => -0.3 }, { 1..5 => 0.4 }]
 
-    assert_template_result(expected_output, template, { "products" => TestDeepEnumerable.new })
+    assert_equal(1, @filters.sum(input, true))
+    assert_equal(0.2, @filters.sum(input, 1.0))
+    assert_equal(-0.3, @filters.sum(input, 1))
+    assert_equal(0.4, @filters.sum(input, 1..5))
+    assert_equal(0, @filters.sum(input, nil))
+    assert_equal(0, @filters.sum(input, ""))
+  end
+
+  def test_uniq_with_to_liquid_value
+    input = [StringDrop.new("foo"), StringDrop.new("bar"), "foo"]
+    expected = [StringDrop.new("foo"), StringDrop.new("bar")]
+    result = @filters.uniq(input)
+
+    assert_equal(expected, result)
+  end
+
+  def test_uniq_with_to_liquid_value_pick_correct_classes
+    input = ["foo", StringDrop.new("foo"), StringDrop.new("bar")]
+    expected = [String, StringDrop]
+    result = @filters.uniq(input).map(&:class)
+
+    assert_equal(expected, result)
   end
 
   private

test/integration/tags/cycle_tag_test.rb

@@ -3,20 +3,10 @@
 require 'test_helper'
 
 class CycleTagTest < Minitest::Test
-  def test_simple_cycle
-    template = <<~LIQUID
-      {%- cycle '1', '2', '3' -%}
-      {%- cycle '1', '2', '3' -%}
-      {%- cycle '1', '2', '3' -%}
-    LIQUID
-
-    assert_template_result("123", template)
-  end
-
   def test_simple_cycle_inside_for_loop
     template = <<~LIQUID
       {%- for i in (1..3) -%}
-        {% cycle '1', '2', '3' %}
+        {%- cycle '1', '2', '3' -%}
       {%- endfor -%}
     LIQUID
 
@@ -36,13 +26,128 @@ class CycleTagTest < Minitest::Test
     assert_template_result("123", template)
   end
 
-  def test_cycle_tag_always_resets_cycle
+  def test_cycle_named_groups_string
     template = <<~LIQUID
-      {%- assign a = "1" -%}
-      {%- cycle a, "2" -%}
-      {%- cycle a, "2" -%}
+      {%- for i in (1..3) -%}
+        {%- cycle 'placeholder1': 1, 2, 3 -%}
+        {%- cycle 'placeholder2': 1, 2, 3 -%}
+      {%- endfor -%}
     LIQUID
 
-    assert_template_result("11", template)
+    assert_template_result("112233", template)
+  end
+
+  def test_cycle_named_groups_vlookup
+    template = <<~LIQUID
+      {%- assign placeholder1 = 'placeholder1' -%}
+      {%- assign placeholder2 = 'placeholder2' -%}
+      {%- for i in (1..3) -%}
+        {%- cycle placeholder1: 1, 2, 3 -%}
+        {%- cycle placeholder2: 1, 2, 3 -%}
+      {%- endfor -%}
+    LIQUID
+
+    assert_template_result("112233", template)
+  end
+
+  def test_unnamed_cycle_have_independent_counters_when_used_with_lookups
+    template = <<~LIQUID
+      {%- assign a = "1" -%}
+      {%- for i in (1..3) -%}
+        {%- cycle a, "2" -%}
+        {%- cycle a, "2" -%}
+      {%- endfor -%}
+    LIQUID
+
+    assert_template_result("112211", template)
+  end
+
+  def test_unnamed_cycle_dependent_counter_when_used_with_literal_values
+    template = <<~LIQUID
+      {%- cycle "1", "2" -%}
+      {%- cycle "1", "2" -%}
+      {%- cycle "1", "2" -%}
+    LIQUID
+
+    assert_template_result("121", template)
+  end
+
+  def test_optional_trailing_comma
+    template = <<~LIQUID
+      {%- cycle "1", "2", -%}
+      {%- cycle "1", "2", -%}
+      {%- cycle "1", "2", -%}
+      {%- cycle "1", -%}
+    LIQUID
+
+    assert_template_result("1211", template)
+  end
+
+  def test_cycle_tag_without_arguments
+    error = assert_raises(Liquid::SyntaxError) do
+      Template.parse("{% cycle %}")
+    end
+
+    assert_match(/Syntax Error in 'cycle' - Valid syntax: cycle \[name :\] var/, error.message)
+  end
+
+  def test_cycle_tag_unsupported_legacy_quirk
+    # QuotedFragment is more permissive than what Parser#expression allows.
+    template1 = "{% assign 5 = 'b' %}{% cycle .5, .4 %}"
+    template2 = "{% cycle .5: 'a', 'b' %}"
+
+    error1 = assert_raises(Liquid::SyntaxError) { Template.parse(template1) }
+    error2 = assert_raises(Liquid::SyntaxError) { Template.parse(template2) }
+
+    expected_error = /Liquid syntax error: \[:dot, "."\] is not a valid expression/
+
+    assert_match(expected_error, error1.message)
+    assert_match(expected_error, error2.message)
+  end
+
+  def test_cycle_with_trailing_elements_legacy_syntax
+    assignments = "{% assign a = 'A' %}{% assign n = 'N' %}"
+
+    template1 = "#{assignments}{% cycle       'a'  'b', 'c' %}"
+    template2 = "#{assignments}{% cycle name: 'a'  'b', 'c' %}"
+    template3 = "#{assignments}{% cycle name: 'a', 'b'  'c' %}"
+    template4 = "#{assignments}{% cycle n  e: 'a', 'b', 'c' %}"
+    template5 = "#{assignments}{% cycle n  e  'a', 'b', 'c' %}"
+
+    error1 = assert_raises(Liquid::SyntaxError) { Template.parse(template1) }
+    error2 = assert_raises(Liquid::SyntaxError) { Template.parse(template2) }
+    error3 = assert_raises(Liquid::SyntaxError) { Template.parse(template3) }
+    error4 = assert_raises(Liquid::SyntaxError) { Template.parse(template4) }
+    error5 = assert_raises(Liquid::SyntaxError) { Template.parse(template5) }
+
+    expected_error = /Expected end_of_string but found/
+
+    assert_match(expected_error, error1.message)
+    assert_match(expected_error, error2.message)
+    assert_match(expected_error, error3.message)
+    assert_match(expected_error, error4.message)
+    assert_match(expected_error, error5.message)
+  end
+
+  def test_cycle_name_with_invalid_expression
+    template = <<~LIQUID
+      {% for i in (1..3) %}
+        {% cycle foo=>bar: "a", "b" %}
+      {% endfor %}
+    LIQUID
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
+
+  def test_cycle_variable_with_invalid_expression
+    template = <<~LIQUID
+      {% for i in (1..3) %}
+        {% cycle foo=>bar, "a", "b" %}
+      {% endfor %}
+    LIQUID
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
   end
 end

test/integration/tags/include_tag_test.rb

@@ -204,6 +204,22 @@ class IncludeTagTest < Minitest::Test
     )
   end
 
+  def test_parsing_errors_for_legacy_quirk
+    assert_syntax_error(
+      '{% include "snippet" !!! arg1: "value1" ~~~ arg2: "value2" %}',
+    )
+    assert_syntax_error(
+      '{% include "snippet" | filter %}',
+    )
+  end
+
+  def test_optional_commas
+    partials = { 'snippet' => 'hello {{ arg1 }} {{ arg2 }}' }
+    assert_template_result('hello value1 value2', '{% include "snippet", arg1: "value1", arg2: "value2" %}', partials: partials)
+    assert_template_result('hello value1 value2', '{% include "snippet"  arg1: "value1", arg2: "value2" %}', partials: partials)
+    assert_template_result('hello value1 value2', '{% include "snippet"  arg1: "value1"  arg2: "value2" %}', partials: partials)
+  end
+
   def test_include_tag_caches_second_read_of_same_partial
     file_system = CountingFileSystem.new
     environment = Liquid::Environment.build(file_system: file_system)
@@ -275,16 +291,10 @@ class IncludeTagTest < Minitest::Test
     env = Liquid::Environment.build(file_system: TestFileSystem.new)
 
     assert_raises(Liquid::SyntaxError) do
-      Template.parse("{% include template %}", error_mode: :strict, environment: env).render!("template" => '{{ "X" || downcase }}')
-    end
-    with_error_mode(:lax) do
-      assert_equal('x', Template.parse("{% include template %}", error_mode: :strict, include_options_blacklist: true, environment: env).render!("template" => '{{ "X" || downcase }}'))
+      Template.parse("{% include template %}", environment: env).render!("template" => '{{ "X" || downcase }}')
     end
     assert_raises(Liquid::SyntaxError) do
-      Template.parse("{% include template %}", error_mode: :strict, include_options_blacklist: [:locale], environment: env).render!("template" => '{{ "X" || downcase }}')
-    end
-    with_error_mode(:lax) do
-      assert_equal('x', Template.parse("{% include template %}", error_mode: :strict, include_options_blacklist: [:error_mode], environment: env).render!("template" => '{{ "X" || downcase }}'))
+      Template.parse("{% include template %}", include_options_blacklist: [:locale], environment: env).render!("template" => '{{ "X" || downcase }}')
     end
   end
 
@@ -339,7 +349,7 @@ class IncludeTagTest < Minitest::Test
       file_system: StubFileSystem.new('simple' => 'simple'),
     )
 
-    template = Liquid::Template.parse("{% include 'simple' %}", error_mode: :warn, environment: env)
+    template = Liquid::Template.parse("{% include 'simple' %}", environment: env)
     template.render(nil, strict_variables: true)
 
     assert_equal([], template.errors)
@@ -374,4 +384,25 @@ class IncludeTagTest < Minitest::Test
       render_errors: true,
     )
   end
+
+  def test_include_template_with_invalid_expression
+    template = "{% include foo=>bar %}"
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
+
+  def test_include_with_invalid_expression
+    template = '{% include "snippet" with foo=>bar %}'
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
+
+  def test_include_attribute_with_invalid_expression
+    template = '{% include "snippet", key: foo=>bar %}'
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
 end # IncludeTagTest

test/integration/tags/render_tag_test.rb

@@ -105,7 +105,23 @@ class RenderTagTest < Minitest::Test
     assert_syntax_error("{% assign name = 'snippet' %}{% render name %}")
   end
 
-  def test_include_tag_caches_second_read_of_same_partial
+  def test_parsing_errors_legacy_syntax
+    assert_syntax_error(
+      '{% render "snippet" !!! arg1: "value1" ~~~ arg2: "value2" %}',
+    )
+    assert_syntax_error(
+      '{% render "snippet" | filter %}',
+    )
+  end
+
+  def test_optional_commas
+    partials = { 'snippet' => 'hello {{ arg1 }} {{ arg2 }}' }
+    assert_template_result('hello value1 value2', '{% render "snippet", arg1: "value1", arg2: "value2" %}', partials: partials)
+    assert_template_result('hello value1 value2', '{% render "snippet"  arg1: "value1", arg2: "value2" %}', partials: partials)
+    assert_template_result('hello value1 value2', '{% render "snippet"  arg1: "value1"  arg2: "value2" %}', partials: partials)
+  end
+
+  def test_render_tag_caches_second_read_of_same_partial
     file_system = StubFileSystem.new('snippet' => 'echo')
     assert_equal(
       'echoecho',
@@ -288,4 +304,16 @@ class RenderTagTest < Minitest::Test
       render_errors: true,
     )
   end
+
+  def test_render_with_invalid_expression
+    template = '{% render "snippet" with foo=>bar %}'
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
+
+  def test_render_attribute_with_invalid_expression
+    template = '{% render "snippet", key: foo=>bar %}'
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
 end

test/integration/tags/standard_tag_test.rb

@@ -117,7 +117,7 @@ class StandardTagTest < Minitest::Test
     assigns = { 'condition' => "bad string here" }
     assert_template_result(
       '',
-      '{% case condition %}{% when "string here" %} hit {% endcase %}',\
+      '{% case condition %}{% when "string here" %} hit {% endcase %}',
       assigns,
     )
   end

test/integration/tags/table_row_test.rb

@@ -138,7 +138,7 @@ class TableRowTest < Minitest::Test
 
   def test_tablerow_loop_drop_attributes
     template = <<~LIQUID.chomp
-      {% tablerow i in (1...2) %}
+      {% tablerow i in (1..2) %}
       col: {{ tablerowloop.col }}
       col0: {{ tablerowloop.col0 }}
       col_first: {{ tablerowloop.col_first }}
@@ -188,35 +188,15 @@ class TableRowTest < Minitest::Test
     assert_template_result(expected_output, template)
   end
 
-  def test_table_row_renders_correct_error_message_for_invalid_parameters
-    assert_template_result(
-      "Liquid error (line 1): invalid integer",
-      '{% tablerow n in (1...10) limit:true %} {{n}} {% endtablerow %}',
-      render_errors: true,
-    )
-
-    assert_template_result(
-      "Liquid error (line 1): invalid integer",
-      '{% tablerow n in (1...10) offset:true %} {{n}} {% endtablerow %}',
-      render_errors: true,
-    )
-
-    assert_template_result(
-      "Liquid error (line 1): invalid integer",
-      '{% tablerow n in (1...10) cols:true %} {{n}} {% endtablerow %}',
-      render_errors: true,
-    )
-  end
-
   def test_table_row_handles_interrupts
     assert_template_result(
       "<tr class=\"row1\">\n<td class=\"col1\"> 1 </td></tr>\n",
-      '{% tablerow n in (1...3) cols:2 %} {{n}} {% break %} {{n}} {% endtablerow %}',
+      '{% tablerow n in (1..3) cols:2 %} {{n}} {% break %} {{n}} {% endtablerow %}',
     )
 
     assert_template_result(
       "<tr class=\"row1\">\n<td class=\"col1\"> 1 </td><td class=\"col2\"> 2 </td></tr>\n<tr class=\"row2\"><td class=\"col1\"> 3 </td></tr>\n",
-      '{% tablerow n in (1...3) cols:2 %} {{n}} {% continue %} {{n}} {% endtablerow %}',
+      '{% tablerow n in (1..3) cols:2 %} {{n}} {% continue %} {{n}} {% endtablerow %}',
     )
   end
 
@@ -255,4 +235,164 @@ class TableRowTest < Minitest::Test
       template,
     )
   end
+
+  def test_tablerow_with_cols_attribute
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..6) cols: 3 %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td><td class="col3">3</td></tr>
+      <tr class="row2"><td class="col1">4</td><td class="col2">5</td><td class="col3">6</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_with_limit_attribute
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..10) limit: 3 %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td><td class="col3">3</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_with_offset_attribute
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..5) offset: 2 %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">3</td><td class="col2">4</td><td class="col3">5</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_with_range_attribute
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..3) range: (1..10) %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td><td class="col3">3</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_with_multiple_attributes
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..10) cols: 2, limit: 4, offset: 1 %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">2</td><td class="col2">3</td></tr>
+      <tr class="row2"><td class="col1">4</td><td class="col2">5</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_with_variable_collection
+    template = <<~LIQUID.chomp
+      {% tablerow n in numbers cols: 2 %}{{ n }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td></tr>
+      <tr class="row2"><td class="col1">3</td><td class="col2">4</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template, { 'numbers' => [1, 2, 3, 4] })
+  end
+
+  def test_tablerow_with_dotted_access
+    template = <<~LIQUID.chomp
+      {% tablerow n in obj.numbers cols: 2 %}{{ n }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td></tr>
+      <tr class="row2"><td class="col1">3</td><td class="col2">4</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template, { 'obj' => { 'numbers' => [1, 2, 3, 4] } })
+  end
+
+  def test_tablerow_with_bracketed_access
+    template = <<~LIQUID.chomp
+      {% tablerow n in obj["numbers"] cols: 2 %}{{ n }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">10</td><td class="col2">20</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template, { 'obj' => { 'numbers' => [10, 20] } })
+  end
+
+  def test_tablerow_without_attributes
+    template = <<~LIQUID.chomp
+      {% tablerow i in (1..3) %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      <td class="col1">1</td><td class="col2">2</td><td class="col3">3</td></tr>
+    OUTPUT
+
+    assert_template_result(expected, template)
+  end
+
+  def test_tablerow_without_in_keyword
+    template = '{% tablerow i (1..10) %}{{ i }}{% endtablerow %}'
+
+    error = assert_raises(SyntaxError) { Template.parse(template) }
+    assert_equal("Liquid syntax error: For loops require an 'in' clause in \"i (1..10)\"", error.message)
+  end
+
+  def test_tablerow_with_multiple_invalid_attributes_reports_first
+    template = '{% tablerow i in (1..10) invalid1: 5, invalid2: 10 %}{{ i }}{% endtablerow %}'
+
+    error = assert_raises(SyntaxError) { Template.parse(template) }
+    assert_equal("Liquid syntax error: Invalid attribute 'invalid1' in tablerow loop. Valid attributes are cols, limit, offset, and range in \"i in (1..10) invalid1: 5, invalid2: 10\"", error.message)
+  end
+
+  def test_tablerow_with_empty_collection
+    template = <<~LIQUID.chomp
+      {% tablerow i in empty_array cols: 2 %}{{ i }}{% endtablerow %}
+    LIQUID
+
+    expected = <<~OUTPUT
+      <tr class="row1">
+      </tr>
+    OUTPUT
+
+    assert_template_result(expected, template, { 'empty_array' => [] })
+  end
+
+  def test_tablerow_with_invalid_attribute
+    template = '{% tablerow i in (1..5) invalid_attr: 10 %}{{ i }}{% endtablerow %}'
+    error = assert_raises(SyntaxError) { Template.parse(template) }
+    assert_match(/Invalid attribute 'invalid_attr'/, error.message)
+  end
+
+  def test_tablerow_with_invalid_expression
+    template = '{% tablerow i in (1..5) limit: foo=>bar %}{{ i }}{% endtablerow %}'
+    error = assert_raises(SyntaxError) { Template.parse(template) }
+    assert_match(/Unexpected character =/, error.message)
+  end
 end

test/integration/template_test.rb

@@ -44,16 +44,6 @@ class TemplateTest < Minitest::Test
     assert_equal('from instance assigns', t.parse("{{ foo }}").render!)
   end
 
-  def test_warnings_is_not_exponential_time
-    str = "false"
-    100.times do
-      str = "{% if true %}true{% else %}#{str}{% endif %}"
-    end
-
-    t = Template.parse(str)
-    assert_equal([], Timeout.timeout(1) { t.warnings })
-  end
-
   def test_instance_assigns_persist_on_same_template_parsing_between_renders
     t = Template.new.parse("{{ foo }}{% assign foo = 'foo' %}{{ foo }}")
     assert_equal('foo', t.render!)
@@ -133,7 +123,7 @@ class TemplateTest < Minitest::Test
     assert(t.resource_limits.reached?)
 
     t.resource_limits.render_score_limit = 200
-    assert_equal((" foo " * 100), t.render!)
+    assert_equal(" foo " * 100, t.render!)
     refute_nil(t.resource_limits.render_score)
   end
 
@@ -259,7 +249,7 @@ class TemplateTest < Minitest::Test
   end
 
   def test_nil_value_does_not_raise
-    t      = Template.parse("some{{x}}thing", error_mode: :strict)
+    t      = Template.parse("some{{x}}thing")
     result = t.render!({ 'x' => nil }, strict_variables: true)
 
     assert_equal(0, t.errors.count)

test/integration/variable_test.rb

@@ -176,37 +176,33 @@ class VariableTest < Minitest::Test
     )
   end
 
-  def test_variable_lookup_should_not_hang_with_invalid_syntax
-    Timeout.timeout(1) do
-      assert_template_result(
-        'bar',
-        "{{['foo'}}",
-        {
-          'foo' => 'bar',
-        },
-        error_mode: :lax,
-      )
-    end
+  def test_filter_with_single_trailing_comma
+    template = '{{ "hello" | append: "world", }}'
 
-    very_long_key = "1234567890" * 100
+    assert_template_result('helloworld', template)
+  end
 
-    template_list = [
-      "{{['#{very_long_key}']}}", # valid
-      "{{['#{very_long_key}'}}", # missing closing bracket
-      "{{[['#{very_long_key}']}}", # extra open bracket
-    ]
+  def test_multiple_filters_with_trailing_commas
+    template = '{{ "hello" | append: "1", | append: "2", }}'
 
-    template_list.each do |template|
-      Timeout.timeout(1) do
-        assert_template_result(
-          'bar',
-          template,
-          {
-            very_long_key => 'bar',
-          },
-          error_mode: :lax,
-        )
-      end
-    end
+    assert_template_result('hello12', template)
+  end
+
+  def test_filter_with_colon_but_no_arguments
+    template = '{{ "test" | upcase: }}'
+
+    assert_template_result('TEST', template)
+  end
+
+  def test_filter_chain_with_colon_no_args
+    template = '{{ "test" | append: "x" | upcase: }}'
+
+    assert_template_result('TESTX', template)
+  end
+
+  def test_combining_trailing_comma_and_empty_args
+    template = '{{ "test" | append: "x", | upcase: }}'
+
+    assert_template_result('TESTX', template)
   end
 end

test/test_helper.rb

@@ -8,13 +8,6 @@ $LOAD_PATH.unshift(File.join(File.expand_path(__dir__), '..', 'lib'))
 require 'liquid.rb'
 require 'liquid/profiler'
 
-mode = :strict
-if (env_mode = ENV['LIQUID_PARSER_MODE'])
-  puts "-- #{env_mode.upcase} ERROR MODE"
-  mode = env_mode.to_sym
-end
-Liquid::Environment.default.error_mode = mode
-
 if Minitest.const_defined?('Test')
   # We're on Minitest 5+. Nothing to do here.
 else
@@ -34,27 +27,27 @@ module Minitest
 
     def assert_template_result(
       expected, template, assigns = {},
-      message: nil, partials: nil, error_mode: nil, render_errors: false,
+      message: nil, partials: nil, render_errors: false,
       template_factory: nil
     )
       file_system = StubFileSystem.new(partials || {})
       environment = Liquid::Environment.build(file_system: file_system)
-      template = Liquid::Template.parse(template, line_numbers: true, error_mode: error_mode&.to_sym, environment: environment)
+      template = Liquid::Template.parse(template, line_numbers: true, environment: environment)
       registers = Liquid::Registers.new(file_system: file_system, template_factory: template_factory)
       context = Liquid::Context.build(static_environments: assigns, rethrow_errors: !render_errors, registers: registers, environment: environment)
       output = template.render(context)
       assert_equal(expected, output, message)
     end
 
-    def assert_match_syntax_error(match, template, error_mode: nil)
+    def assert_match_syntax_error(match, template)
       exception = assert_raises(Liquid::SyntaxError) do
-        Template.parse(template, line_numbers: true, error_mode: error_mode&.to_sym).render
+        Template.parse(template, line_numbers: true).render
       end
       assert_match(match, exception.message)
     end
 
-    def assert_syntax_error(template, error_mode: nil)
-      assert_match_syntax_error("", template, error_mode: error_mode)
+    def assert_syntax_error(template)
+      assert_match_syntax_error("", template)
     end
 
     def assert_usage_increment(name, times: 1)
@@ -82,14 +75,6 @@ module Minitest
       Environment.dangerously_override(environment, &blk)
     end
 
-    def with_error_mode(mode)
-      old_mode = Liquid::Environment.default.error_mode
-      Liquid::Environment.default.error_mode = mode
-      yield
-    ensure
-      Liquid::Environment.default.error_mode = old_mode
-    end
-
     def with_custom_tag(tag_name, tag_class, &block)
       environment = Liquid::Environment.default.dup
       environment.register_tag(tag_name, tag_class)
@@ -146,6 +131,35 @@ class BooleanDrop < Liquid::Drop
   end
 end
 
+class StringDrop < Liquid::Drop
+  include Comparable
+
+  def initialize(value)
+    super()
+    @value = value
+  end
+
+  def to_liquid_value
+    @value
+  end
+
+  def to_s
+    @value
+  end
+
+  def to_str
+    @value
+  end
+
+  def inspect
+    "#<StringDrop @value=#{@value.inspect}>"
+  end
+
+  def <=>(other)
+    to_liquid_value <=> Liquid::Utils.to_liquid_value(other)
+  end
+end
+
 class ErrorDrop < Liquid::Drop
   def standard_error
     raise Liquid::StandardError, 'standard error'
@@ -168,6 +182,26 @@ class ErrorDrop < Liquid::Drop
   end
 end
 
+class CustomToLiquidDrop < Liquid::Drop
+  def initialize(value)
+    @value = value
+    super()
+  end
+
+  def to_liquid
+    @value
+  end
+end
+
+class HashWithCustomToS < Hash
+  def to_s
+    "kewl"
+  end
+end
+
+class HashWithoutCustomToS < Hash
+end
+
 class StubFileSystem
   attr_reader :file_read_count
 

test/unit/block_unit_test.rb

@@ -47,12 +47,18 @@ class BlockUnitTest < Minitest::Test
     )
   end
 
-  def test_with_block
+  def test_comment_tag_with_block
     template = Liquid::Template.parse("  {% comment %} {% endcomment %} ")
     assert_equal([String, Comment, String], block_types(template.root.nodelist))
     assert_equal(3, template.root.nodelist.size)
   end
 
+  def test_doc_tag_with_block
+    template = Liquid::Template.parse("  {% doc %} {% enddoc %} ")
+    assert_equal([String, Doc, String], block_types(template.root.nodelist))
+    assert_equal(3, template.root.nodelist.size)
+  end
+
   private
 
   def block_types(nodelist)

test/unit/condition_unit_test.rb

@@ -82,7 +82,7 @@ class ConditionUnitTest < Minitest::Test
   def test_contains_works_on_arrays
     @context          = Liquid::Context.new
     @context['array'] = [1, 2, 3, 4, 5]
-    array_expr        = VariableLookup.new("array")
+    array_expr        = VariableLookup.parse("array")
 
     assert_evaluates_false(array_expr, 'contains', 0)
     assert_evaluates_true(array_expr, 'contains', 1)
@@ -96,8 +96,8 @@ class ConditionUnitTest < Minitest::Test
 
   def test_contains_returns_false_for_nil_operands
     @context = Liquid::Context.new
-    assert_evaluates_false(VariableLookup.new('not_assigned'), 'contains', '0')
-    assert_evaluates_false(0, 'contains', VariableLookup.new('not_assigned'))
+    assert_evaluates_false(VariableLookup.parse('not_assigned'), 'contains', '0')
+    assert_evaluates_false(0, 'contains', VariableLookup.parse('not_assigned'))
   end
 
   def test_contains_return_false_on_wrong_data_type
@@ -149,7 +149,7 @@ class ConditionUnitTest < Minitest::Test
     @context        = Liquid::Context.new
     @context['one'] = @context['another'] = "gnomeslab-and-or-liquid"
 
-    assert_evaluates_true(VariableLookup.new("one"), '==', VariableLookup.new("another"))
+    assert_evaluates_true(VariableLookup.parse("one"), '==', VariableLookup.parse("another"))
   end
 
   def test_default_context_is_deprecated
@@ -161,11 +161,197 @@ class ConditionUnitTest < Minitest::Test
       assert_equal(true, Condition.new(1, '==', 1).evaluate)
     end
 
-    expected = "DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated" \
-      " and will be removed from Liquid 6.0.0."
+    expected = "DEPRECATION WARNING: Condition#evaluate without a context argument is deprecated " \
+      "and will be removed from Liquid 6.0.0."
     assert_includes(err.lines.map(&:strip), expected)
   end
 
+  def test_parse_expression
+    environment = Environment.build
+    parse_context = ParseContext.new(environment: environment)
+    parser = parse_context.new_parser('product.title')
+    result = Condition.parse_expression(parser)
+
+    assert_instance_of(VariableLookup, result)
+    assert_equal('product', result.name)
+    assert_equal(['title'], result.lookups)
+  end
+
+  def test_parse_expression_returns_method_literal_for_blank_and_empty
+    environment = Environment.build
+    parse_context = ParseContext.new(environment: environment)
+    parser = parse_context.new_parser('blank')
+    result = Condition.parse_expression(parser)
+
+    assert_instance_of(Condition::MethodLiteral, result)
+  end
+
+  # Tests for blank? comparison without ActiveSupport
+  #
+  # Ruby's standard library does not include blank? on String, Array, Hash, etc.
+  # ActiveSupport adds blank? but Liquid must work without it. These tests verify
+  # that Liquid implements blank? semantics internally for use in templates like:
+  #   {% if x == blank %}...{% endif %}
+  #
+  # The blank? semantics match ActiveSupport's behavior:
+  # - nil and false are blank
+  # - Strings are blank if empty or contain only whitespace
+  # - Arrays and Hashes are blank if empty
+  # - true and numbers are never blank
+
+  def test_blank_with_whitespace_string
+    # Template authors expect "   " to be blank since it has no visible content.
+    # This matches ActiveSupport's String#blank? which returns true for whitespace-only strings.
+    @context['whitespace'] = '   '
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('whitespace'), '==', blank_literal)
+  end
+
+  def test_blank_with_empty_string
+    # An empty string has no content, so it should be considered blank.
+    # This is the most basic case of a blank string.
+    @context['empty_string'] = ''
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('empty_string'), '==', blank_literal)
+  end
+
+  def test_blank_with_empty_array
+    # Empty arrays have no elements, so they are blank.
+    # Useful for checking if a collection has items: {% if products == blank %}
+    @context['empty_array'] = []
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('empty_array'), '==', blank_literal)
+  end
+
+  def test_blank_with_empty_hash
+    # Empty hashes have no key-value pairs, so they are blank.
+    # Useful for checking if settings/options exist: {% if settings == blank %}
+    @context['empty_hash'] = {}
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('empty_hash'), '==', blank_literal)
+  end
+
+  def test_blank_with_nil
+    # nil represents "nothing" and is the canonical blank value.
+    # Unassigned variables resolve to nil, so this enables: {% if missing_var == blank %}
+    @context['nil_value'] = nil
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('nil_value'), '==', blank_literal)
+  end
+
+  def test_blank_with_false
+    # false is considered blank to match ActiveSupport semantics.
+    # This allows {% if some_flag == blank %} to work when flag is false.
+    @context['false_value'] = false
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_true(VariableLookup.parse('false_value'), '==', blank_literal)
+  end
+
+  def test_not_blank_with_true
+    # true is a definite value, not blank.
+    # Ensures {% if flag == blank %} works correctly for boolean flags.
+    @context['true_value'] = true
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_false(VariableLookup.parse('true_value'), '==', blank_literal)
+  end
+
+  def test_not_blank_with_number
+    # Numbers (including zero) are never blank - they represent actual values.
+    # 0 is a valid quantity, not the absence of a value.
+    @context['number'] = 42
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_false(VariableLookup.parse('number'), '==', blank_literal)
+  end
+
+  def test_not_blank_with_string_content
+    # A string with actual content is not blank.
+    # This is the expected behavior for most template string comparisons.
+    @context['string'] = 'hello'
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_false(VariableLookup.parse('string'), '==', blank_literal)
+  end
+
+  def test_not_blank_with_non_empty_array
+    # An array with elements has content, so it's not blank.
+    # Enables patterns like {% unless products == blank %}Show products{% endunless %}
+    @context['array'] = [1, 2, 3]
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_false(VariableLookup.parse('array'), '==', blank_literal)
+  end
+
+  def test_not_blank_with_non_empty_hash
+    # A hash with key-value pairs has content, so it's not blank.
+    # Useful for checking if configuration exists: {% if config != blank %}
+    @context['hash'] = { 'a' => 1 }
+    blank_literal = Condition.class_variable_get(:@@method_literals)['blank']
+
+    assert_evaluates_false(VariableLookup.parse('hash'), '==', blank_literal)
+  end
+
+  # Tests for empty? comparison without ActiveSupport
+  #
+  # empty? is distinct from blank? - it only checks if a collection has zero elements.
+  # For strings, empty? checks length == 0, NOT whitespace content.
+  # Ruby's standard library has empty? on String, Array, and Hash, but Liquid
+  # provides a fallback implementation for consistency.
+
+  def test_empty_with_empty_string
+    # An empty string ("") has length 0, so it's empty.
+    # Different from blank - empty is a stricter check.
+    @context['empty_string'] = ''
+    empty_literal = Condition.class_variable_get(:@@method_literals)['empty']
+
+    assert_evaluates_true(VariableLookup.parse('empty_string'), '==', empty_literal)
+  end
+
+  def test_empty_with_whitespace_string_not_empty
+    # Whitespace strings have length > 0, so they are NOT empty.
+    # This is the key difference between empty and blank:
+    # "   ".empty? => false, but "   ".blank? => true
+    @context['whitespace'] = '   '
+    empty_literal = Condition.class_variable_get(:@@method_literals)['empty']
+
+    assert_evaluates_false(VariableLookup.parse('whitespace'), '==', empty_literal)
+  end
+
+  def test_empty_with_empty_array
+    # An array with no elements is empty.
+    # [].empty? => true
+    @context['empty_array'] = []
+    empty_literal = Condition.class_variable_get(:@@method_literals)['empty']
+
+    assert_evaluates_true(VariableLookup.parse('empty_array'), '==', empty_literal)
+  end
+
+  def test_empty_with_empty_hash
+    # A hash with no key-value pairs is empty.
+    # {}.empty? => true
+    @context['empty_hash'] = {}
+    empty_literal = Condition.class_variable_get(:@@method_literals)['empty']
+
+    assert_evaluates_true(VariableLookup.parse('empty_hash'), '==', empty_literal)
+  end
+
+  def test_nil_is_not_empty
+    # nil is NOT empty - empty? checks if a collection has zero elements.
+    # nil is not a collection, so it cannot be empty.
+    # This differs from blank: nil IS blank, but nil is NOT empty.
+    @context['nil_value'] = nil
+    empty_literal = Condition.class_variable_get(:@@method_literals)['empty']
+
+    assert_evaluates_false(VariableLookup.parse('nil_value'), '==', empty_literal)
+  end
+
   private
 
   def assert_evaluates_true(left, op, right)

test/unit/environment_test.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class EnvironmentTest < Minitest::Test
+  include Liquid
+
+  class UnsubscribeFooter < Liquid::Tag
+    def render(_context)
+      'Unsubscribe Footer'
+    end
+  end
+
+  def test_custom_tag
+    email_environment = Liquid::Environment.build do |environment|
+      environment.register_tag("unsubscribe_footer", UnsubscribeFooter)
+    end
+
+    assert(email_environment.tags["unsubscribe_footer"])
+    assert(email_environment.tag_for_name("unsubscribe_footer"))
+    template = Liquid::Template.parse("{% unsubscribe_footer %}", environment: email_environment)
+
+    assert_equal('Unsubscribe Footer', template.render)
+  end
+end

test/unit/lexer_unit_test.rb

@@ -131,6 +131,16 @@ class LexerUnitTest < Minitest::Test
     assert_equal([[:id, "false"], [:number, "1"], [:end_of_string]], tokenize("false 1"))
   end
 
+  def test_error_with_invalid_utf8
+    error = assert_raises(SyntaxError) do
+      tokenize("\x00\xff")
+    end
+    assert_equal(
+      'Liquid syntax error: Invalid byte sequence in UTF-8',
+      error.message,
+    )
+  end
+
   private
 
   def tokenize(input)

test/unit/parse_context_unit_test.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class ParseContextUnitTest < Minitest::Test
+  include Liquid
+
+  def test_parser_expression_with_variable_lookup
+    parser = parse_context.new_parser('product.title')
+    result = parser.expression
+
+    assert_instance_of(VariableLookup, result)
+    assert_equal('product', result.name)
+    assert_equal(['title'], result.lookups)
+  end
+
+  def test_parser_expression_raises_syntax_error_for_invalid_expression
+    parser = parse_context.new_parser('')
+
+    error = assert_raises(Liquid::SyntaxError) do
+      parser.expression
+    end
+
+    assert_match(/is not a valid expression/, error.message)
+  end
+
+  def test_parse_expression_with_variable_lookup
+    result = parse_context.new_parser('product.title').expression
+
+    assert_instance_of(VariableLookup, result)
+    assert_equal('product', result.name)
+    assert_equal(['title'], result.lookups)
+  end
+
+  def test_parser_expression_advances_parser_pointer
+    parser = parse_context.new_parser('foo, bar')
+
+    # parser.expression consumes "foo"
+    first_result = parser.expression
+    assert_instance_of(VariableLookup, first_result)
+    assert_equal('foo', first_result.name)
+
+    parser.consume(:comma)
+
+    # parser.expression consumes "bar"
+    second_result = parser.expression
+    assert_instance_of(VariableLookup, second_result)
+    assert_equal('bar', second_result.name)
+
+    parser.consume(:end_of_string)
+  end
+
+  private
+
+  def parse_context
+    @parse_context ||= ParseContext.new(
+      environment: Environment.build,
+    )
+  end
+end

test/unit/parser_unit_test.rb

@@ -45,40 +45,93 @@ class ParserUnitTest < Minitest::Test
     assert_equal(false, p.look(:number, 1))
   end
 
-  def test_expressions
+  def test_expression_string
     p = new_parser("hi.there hi?[5].there? hi.there.bob")
-    assert_equal('hi.there', p.expression)
-    assert_equal('hi?[5].there?', p.expression)
-    assert_equal('hi.there.bob', p.expression)
+    assert_equal('hi.there', p.expression_string)
+    assert_equal('hi?[5].there?', p.expression_string)
+    assert_equal('hi.there.bob', p.expression_string)
 
     p = new_parser("567 6.0 'lol' \"wut\"")
-    assert_equal('567', p.expression)
-    assert_equal('6.0', p.expression)
-    assert_equal("'lol'", p.expression)
-    assert_equal('"wut"', p.expression)
+    assert_equal('567', p.expression_string)
+    assert_equal('6.0', p.expression_string)
+    assert_equal("'lol'", p.expression_string)
+    assert_equal('"wut"', p.expression_string)
+  end
+
+  def test_expression
+    p = new_parser("hi.there hi?[5].there? hi.there.bob")
+    v1 = p.expression
+    v2 = p.expression
+    v3 = p.expression
+    assert(v1.is_a?(VariableLookup) && v1.name == 'hi' && v1.lookups[0] == 'there')
+    assert(v2.is_a?(VariableLookup) && v2.name == 'hi?' && v2.lookups[0] == 5)
+    assert(v3.is_a?(VariableLookup) && v3.name == 'hi' && v3.lookups[0] == 'there')
+
+    p = new_parser("567 6.0 'lol' \"wut\" true false (0..5)")
+    assert_equal(567, p.expression)
+    assert_equal(6.0, p.expression)
+    assert_equal('lol', p.expression)
+    assert_equal('wut', p.expression)
+    assert_equal(true, p.expression)
+    assert_equal(false, p.expression)
+    assert_equal(0..5, p.expression)
+  end
+
+  def test_number
+    p = new_parser('-1 0 1 2.0')
+    assert_equal(-1, p.number)
+    assert_equal(0, p.number)
+    assert_equal(1, p.number)
+    assert_equal(2.0, p.number)
+  end
+
+  def test_string
+    p = new_parser("'s1' \"s2\" 'this \"s3\"' \"that 's4'\"")
+    assert_equal('s1', p.string)
+    assert_equal('s2', p.string)
+    assert_equal('this "s3"', p.string)
+    assert_equal("that 's4'", p.string)
+  end
+
+  def test_unnamed_variable_lookup
+    p = new_parser('[key].title')
+    v = p.expression
+    assert(v.is_a?(VariableLookup))
+    assert(v.name.is_a?(VariableLookup))
+    assert_equal('key', v.name.name)
+    assert_equal('title', v.lookups[0])
+  end
+
+  def test_range_lookup
+    p = new_parser('(0..5) (a..b)')
+    assert_equal(0..5, p.expression)
+
+    r2 = p.expression
+    assert(r2.is_a?(RangeLookup))
+    assert_equal(1..4, r2.evaluate(Context.new({ 'a' => 1, 'b' => 4 })))
   end
 
   def test_ranges
     p = new_parser("(5..7) (1.5..9.6) (young..old) (hi[5].wat..old)")
-    assert_equal('(5..7)', p.expression)
-    assert_equal('(1.5..9.6)', p.expression)
-    assert_equal('(young..old)', p.expression)
-    assert_equal('(hi[5].wat..old)', p.expression)
+    assert_equal('(5..7)', p.expression_string)
+    assert_equal('(1.5..9.6)', p.expression_string)
+    assert_equal('(young..old)', p.expression_string)
+    assert_equal('(hi[5].wat..old)', p.expression_string)
   end
 
-  def test_arguments
+  def test_argument_string
     p = new_parser("filter: hi.there[5], keyarg: 7")
     assert_equal('filter', p.consume(:id))
     assert_equal(':', p.consume(:colon))
-    assert_equal('hi.there[5]', p.argument)
+    assert_equal('hi.there[5]', p.argument_string)
     assert_equal(',', p.consume(:comma))
-    assert_equal('keyarg: 7', p.argument)
+    assert_equal('keyarg: 7', p.argument_string)
   end
 
   def test_invalid_expression
     assert_raises(SyntaxError) do
       p = new_parser("==")
-      p.expression
+      p.expression_string
     end
   end
 

test/unit/partial_cache_unit_test.rb

@@ -175,7 +175,7 @@ class PartialCacheUnitTest < Minitest::Test
     assert_equal('some/path/my_partial', partial.name)
   end
 
-  def test_includes_error_mode_into_template_cache
+  def test_cache_key
     template_factory = StubTemplateFactory.new
     context = Liquid::Context.build(
       registers: {
@@ -184,16 +184,14 @@ class PartialCacheUnitTest < Minitest::Test
       },
     )
 
-    [:lax, :warn, :strict].each do |error_mode|
-      Liquid::PartialCache.load(
-        'my_partial',
-        context: context,
-        parse_context: Liquid::ParseContext.new(error_mode: error_mode),
-      )
-    end
+    Liquid::PartialCache.load(
+      'my_partial',
+      context: context,
+      parse_context: Liquid::ParseContext.new,
+    )
 
     assert_equal(
-      ["my_partial:lax", "my_partial:warn", "my_partial:strict"],
+      ["my_partial"],
       context.registers[:cached_partials].keys,
     )
   end

test/unit/strainer_template_unit_test.rb

@@ -8,7 +8,7 @@ class StrainerTemplateUnitTest < Minitest::Test
   def test_add_filter_when_wrong_filter_class
     c = Context.new
     s = c.strainer
-    wrong_filter = ->(v) { v.reverse }
+    wrong_filter = lambda(&:reverse)
 
     exception = assert_raises(TypeError) do
       s.class.add_filter(wrong_filter)

test/unit/tags/case_tag_unit_test.rb

@@ -9,4 +9,110 @@ class CaseTagUnitTest < Minitest::Test
     template = Liquid::Template.parse('{% case var %}{% when true %}WHEN{% else %}ELSE{% endcase %}')
     assert_equal(['WHEN', 'ELSE'], template.root.nodelist[0].nodelist.map(&:nodelist).flatten)
   end
+
+  def test_case_with_trailing_element
+    template = <<~LIQUID
+      {%- case 1 bar -%}
+        {%- when 1 -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+
+    assert_match(/Expected end_of_string but found/, error.message)
+  end
+
+  def test_case_when_with_trailing_element
+    template = <<~LIQUID
+      {%- case 1 -%}
+        {%- when 1 bar -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template) }
+
+    assert_match(/Expected end_of_string but found/, error.message)
+  end
+
+  def test_case_when_with_comma
+    template = <<~LIQUID
+      {%- case 1 -%}
+        {%- when 2, 1 -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+
+    assert_template_result("one", template)
+  end
+
+  def test_case_when_with_or
+    template = <<~LIQUID
+      {%- case 1 -%}
+        {%- when 2 or 1 -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+
+    assert_template_result("one", template)
+  end
+
+  def test_case_when_empty
+    template = <<~LIQUID
+      {%- case x -%}
+        {%- when 2 or empty -%}
+          2 or empty
+        {%- else -%}
+          not 2 or empty
+      {%- endcase -%}
+    LIQUID
+
+    assert_template_result("2 or empty", template, { 'x' => 2 })
+    assert_template_result("2 or empty", template, { 'x' => {} })
+    assert_template_result("2 or empty", template, { 'x' => [] })
+    assert_template_result("not 2 or empty", template, { 'x' => { 'a' => 'b' } })
+    assert_template_result("not 2 or empty", template, { 'x' => ['a'] })
+    assert_template_result("not 2 or empty", template, { 'x' => 4 })
+  end
+
+  def test_case_with_invalid_expression
+    template = <<~LIQUID
+      {%- case foo=>bar -%}
+        {%- when 'baz' -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+    assigns = { 'foo' => { 'bar' => 'baz' } }
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template, assigns) }
+
+    assert_match(/Unexpected character =/, error.message)
+  end
+
+  def test_case_when_with_invalid_expression
+    template = <<~LIQUID
+      {%- case 'baz' -%}
+        {%- when foo=>bar -%}
+          one
+        {%- else -%}
+          two
+      {%- endcase -%}
+    LIQUID
+    assigns = { 'foo' => { 'bar' => 'baz' } }
+
+    error = assert_raises(Liquid::SyntaxError) { Template.parse(template, assigns) }
+
+    assert_match(/Unexpected character =/, error.message)
+  end
 end

test/unit/tags/doc_tag_unit_test.rb

@@ -0,0 +1,287 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class DocTagUnitTest < Minitest::Test
+  def test_doc_tag
+    template = <<~LIQUID.chomp
+      {% doc %}
+        Renders loading-spinner.
+
+        @param {string} foo - some foo
+        @param {string} [bar] - optional bar
+
+        @example
+        {% render 'loading-spinner', foo: 'foo' %}
+        {% render 'loading-spinner', foo: 'foo', bar: 'bar' %}
+      {% enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_body_content
+    doc_content = "  Documentation content\n  @param {string} foo - test\n"
+    template_source = "{% doc %}#{doc_content}{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal(doc_content, doc_tag.nodelist.first.to_s)
+  end
+
+  def test_doc_tag_does_not_support_extra_arguments
+    error = assert_raises(Liquid::SyntaxError) do
+      template = <<~LIQUID.chomp
+        {% doc extra %}
+        {% enddoc %}
+      LIQUID
+
+      Liquid::Template.parse(template)
+    end
+
+    exp_error = "Liquid syntax error: Syntax Error in 'doc' - Valid syntax: {% doc %}{% enddoc %}"
+    act_error = error.message
+
+    assert_equal(exp_error, act_error)
+  end
+
+  def test_doc_tag_must_support_valid_tags
+    assert_match_syntax_error("Liquid syntax error (line 1): 'doc' tag was never closed", '{% doc %} foo')
+    assert_match_syntax_error("Liquid syntax error (line 1): Syntax Error in 'doc' - Valid syntax: {% doc %}{% enddoc %}", '{% doc } foo {% enddoc %}')
+    assert_match_syntax_error("Liquid syntax error (line 1): Syntax Error in 'doc' - Valid syntax: {% doc %}{% enddoc %}", '{% doc } foo %}{% enddoc %}')
+  end
+
+  def test_doc_tag_ignores_liquid_nodes
+    template = <<~LIQUID.chomp
+      {% doc %}
+        {% if true %}
+        {% if ... %}
+        {%- for ? -%}
+        {% while true %}
+        {%
+          unless if
+        %}
+        {% endcase %}
+      {% enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_ignores_unclosed_liquid_tags
+    template = <<~LIQUID.chomp
+      {% doc %}
+        {% if true %}
+      {% enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_does_not_allow_nested_docs
+    error = assert_raises(Liquid::SyntaxError) do
+      template = <<~LIQUID.chomp
+        {% doc %}
+          {% doc %}
+            {% doc %}
+        {% enddoc %}
+      LIQUID
+
+      Liquid::Template.parse(template)
+    end
+
+    exp_error = "Liquid syntax error: Syntax Error in 'doc' - Nested doc tags are not allowed"
+    act_error = error.message
+
+    assert_equal(exp_error, act_error)
+  end
+
+  def test_doc_tag_ignores_nested_raw_tags
+    template = <<~LIQUID.chomp
+      {% doc %}
+        {% raw %}
+      {% enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_ignores_unclosed_assign
+    template = <<~LIQUID.chomp
+      {% doc %}
+        {% assign foo = "1"
+      {% enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_ignores_malformed_syntax
+    template = <<~LIQUID.chomp
+      {% doc %}
+      {% {{ {%- enddoc %}
+    LIQUID
+
+    assert_template_result('', template)
+  end
+
+  def test_doc_tag_captures_token_before_enddoc
+    template_source = "{% doc %}{{ incomplete{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal("{{ incomplete", doc_tag.nodelist.first.to_s)
+  end
+
+  def test_doc_tag_preserves_error_line_numbers
+    template = Liquid::Template.parse(<<~LIQUID.chomp, line_numbers: true)
+      {% doc %}
+        {% if true %}
+      {% enddoc %}
+      {{ errors.standard_error }}
+    LIQUID
+
+    expected = <<~TEXT.chomp
+
+      Liquid error (line 4): standard error
+    TEXT
+
+    assert_equal(expected, template.render('errors' => ErrorDrop.new))
+  end
+
+  def test_doc_tag_whitespace_control
+    # Basic whitespace control
+    assert_template_result("Hello!", "      {%- doc -%}123{%- enddoc -%}Hello!")
+    assert_template_result("Hello!", "{%- doc -%}123{%- enddoc -%}     Hello!")
+    assert_template_result("Hello!", "      {%- doc -%}123{%- enddoc -%}     Hello!")
+    assert_template_result("Hello!", <<~LIQUID.chomp)
+      {%- doc %}Whitespace control!{% enddoc -%}
+      Hello!
+    LIQUID
+  end
+
+  def test_doc_tag_delimiter_handling
+    assert_template_result('', <<~LIQUID.chomp)
+      {%- if true -%}
+        {%- doc -%}
+          {%- docEXTRA -%}wut{% enddocEXTRA -%}xyz
+        {%- enddoc -%}
+      {%- endif -%}
+    LIQUID
+
+    assert_template_result('', "{% doc %}123{% enddoc xyz %}")
+    assert_template_result('', "{% doc %}123{% enddoc\txyz %}")
+    assert_template_result('', "{% doc %}123{% enddoc\nxyz %}")
+    assert_template_result('', "{% doc %}123{% enddoc\n   xyz  enddoc %}")
+  end
+
+  def test_doc_tag_visitor
+    template_source = '{% doc %}{% enddoc %}'
+
+    assert_equal(
+      [Liquid::Doc],
+      visit(template_source),
+    )
+  end
+
+  def test_doc_tag_blank_with_empty_content
+    template_source = "{% doc %}{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal(true, doc_tag.blank?)
+  end
+
+  def test_doc_tag_blank_with_content
+    template_source = "{% doc %}Some documentation{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal(false, doc_tag.blank?)
+  end
+
+  def test_doc_tag_blank_with_whitespace_only
+    template_source = "{% doc %}    {% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal(false, doc_tag.blank?)
+  end
+
+  def test_doc_tag_nodelist_returns_array_with_body
+    doc_content = "Documentation content\n@param {string} foo"
+    template_source = "{% doc %}#{doc_content}{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal([doc_content], doc_tag.nodelist)
+    assert_equal(1, doc_tag.nodelist.length)
+    assert_equal(doc_content, doc_tag.nodelist.first)
+  end
+
+  def test_doc_tag_nodelist_with_empty_content
+    template_source = "{% doc %}{% enddoc %}"
+
+    doc_tag = nil
+    ParseTreeVisitor
+      .for(Template.parse(template_source).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        doc_tag = tag
+      end
+      .visit
+
+    assert_equal([""], doc_tag.nodelist)
+    assert_equal(1, doc_tag.nodelist.length)
+  end
+
+  private
+
+  def traversal(template)
+    ParseTreeVisitor
+      .for(Template.parse(template).root)
+      .add_callback_for(Liquid::Doc) do |tag|
+        tag_class = tag.class
+        tag_class
+      end
+  end
+
+  def visit(template)
+    traversal(template).visit.flatten.compact
+  end
+end

test/unit/template_unit_test.rb

@@ -35,4 +35,15 @@ class TemplateUnitTest < Minitest::Test
   def test_template_inheritance
     assert_equal("foo", TemplateSubclass.parse("foo").render)
   end
+
+  def test_invalid_utf8
+    input = "\xff\x00"
+    error = assert_raises(SyntaxError) do
+      Liquid::Tokenizer.new(source: input, string_scanner: StringScanner.new(input))
+    end
+    assert_equal(
+      'Liquid syntax error: Invalid byte sequence in UTF-8',
+      error.message,
+    )
+  end
 end

test/unit/variable_unit_test.rb

@@ -7,20 +7,20 @@ class VariableUnitTest < Minitest::Test
 
   def test_variable
     var = create_variable('hello')
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
   end
 
   def test_filters
     var = create_variable('hello | textileze')
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['textileze', []]], var.filters)
 
     var = create_variable('hello | textileze | paragraph')
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['textileze', []], ['paragraph', []]], var.filters)
 
     var = create_variable(%( hello | strftime: '%Y'))
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['strftime', ['%Y']]], var.filters)
 
     var = create_variable(%( 'typo' | link_to: 'Typo', true ))
@@ -44,11 +44,11 @@ class VariableUnitTest < Minitest::Test
     assert_equal([['repeat', [3, 3, 3]]], var.filters)
 
     var = create_variable(%( hello | strftime: '%Y, okay?'))
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['strftime', ['%Y, okay?']]], var.filters)
 
     var = create_variable(%( hello | things: "%Y, okay?", 'the other one'))
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['things', ['%Y, okay?', 'the other one']]], var.filters)
   end
 
@@ -60,24 +60,18 @@ class VariableUnitTest < Minitest::Test
 
   def test_filters_without_whitespace
     var = create_variable('hello | textileze | paragraph')
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['textileze', []], ['paragraph', []]], var.filters)
 
     var = create_variable('hello|textileze|paragraph')
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['textileze', []], ['paragraph', []]], var.filters)
 
     var = create_variable("hello|replace:'foo','bar'|textileze")
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['replace', ['foo', 'bar']], ['textileze', []]], var.filters)
   end
 
-  def test_symbol
-    var = create_variable("http://disney.com/logo.gif | image: 'med' ", error_mode: :lax)
-    assert_equal(VariableLookup.new('http://disney.com/logo.gif'), var.name)
-    assert_equal([['image', ['med']]], var.filters)
-  end
-
   def test_string_to_filter
     var = create_variable("'http://disney.com/logo.gif' | image: 'med' ")
     assert_equal('http://disney.com/logo.gif', var.name)
@@ -105,14 +99,12 @@ class VariableUnitTest < Minitest::Test
   end
 
   def test_dashes
-    assert_equal(VariableLookup.new('foo-bar'), create_variable('foo-bar').name)
-    assert_equal(VariableLookup.new('foo-bar-2'), create_variable('foo-bar-2').name)
+    assert_equal(VariableLookup.parse('foo-bar'), create_variable('foo-bar').name)
+    assert_equal(VariableLookup.parse('foo-bar-2'), create_variable('foo-bar-2').name)
 
-    with_error_mode(:strict) do
-      assert_raises(Liquid::SyntaxError) { create_variable('foo - bar') }
-      assert_raises(Liquid::SyntaxError) { create_variable('-foo') }
-      assert_raises(Liquid::SyntaxError) { create_variable('2foo') }
-    end
+    assert_raises(Liquid::SyntaxError) { create_variable('foo - bar') }
+    assert_raises(Liquid::SyntaxError) { create_variable('-foo') }
+    assert_raises(Liquid::SyntaxError) { create_variable('2foo') }
   end
 
   def test_string_with_special_chars
@@ -122,27 +114,47 @@ class VariableUnitTest < Minitest::Test
 
   def test_string_dot
     var = create_variable(%( test.test ))
-    assert_equal(VariableLookup.new('test.test'), var.name)
+    assert_equal(VariableLookup.parse('test.test'), var.name)
   end
 
   def test_filter_with_keyword_arguments
     var = create_variable(%( hello | things: greeting: "world", farewell: 'goodbye'))
-    assert_equal(VariableLookup.new('hello'), var.name)
+    assert_equal(VariableLookup.parse('hello'), var.name)
     assert_equal([['things', [], { 'greeting' => 'world', 'farewell' => 'goodbye' }]], var.filters)
   end
 
-  def test_lax_filter_argument_parsing
-    var = create_variable(%( number_of_comments | pluralize: 'comment': 'comments' ), error_mode: :lax)
-    assert_equal(VariableLookup.new('number_of_comments'), var.name)
-    assert_equal([['pluralize', ['comment', 'comments']]], var.filters)
-  end
+  def test_filter_argument_parsing
+    # optional colon
+    var = create_variable(%(n | f1 | f2:))
+    assert_equal([['f1', []], ['f2', []]], var.filters)
 
-  def test_strict_filter_argument_parsing
-    with_error_mode(:strict) do
-      assert_raises(SyntaxError) do
-        create_variable(%( number_of_comments | pluralize: 'comment': 'comments' ))
-      end
-    end
+    # missing argument throws error
+    assert_raises(SyntaxError) { create_variable(%(n | f1: ,)) }
+    assert_raises(SyntaxError) { create_variable(%(n | f1: ,| f2)) }
+
+    # arg requires colon
+    assert_raises(SyntaxError) { create_variable(%(n | f1 1)) }
+
+    # trailing comma doesn't throw
+    create_variable(%(n | f1: 1, 2, 3, | f2:))
+
+    # missing comma throws error
+    assert_raises(SyntaxError) { create_variable(%(n | filter: 1 2, 3)) }
+
+    # positional and kwargs parsing
+    var = create_variable(%(n | filter: 1, 2, 3 | filter2: k1: 1, k2: 2))
+    assert_equal([['filter', [1, 2, 3]], ['filter2', [], { "k1" => 1, "k2" => 2 }]], var.filters)
+
+    # positional and kwargs mixed
+    var = create_variable(%(n | filter: 'a', 'b', key1: 1, key2: 2, 'c'))
+    assert_equal([["filter", ["a", "b", "c"], { "key1" => 1, "key2" => 2 }]], var.filters)
+
+    # positional and kwargs intermixed (pos1, key1: val1, pos2)
+    var = create_variable(%(n | link_to: class: "black", "https://example.com", title: "title"))
+    assert_equal([['link_to', ["https://example.com"], { "class" => "black", "title" => "title" }]], var.filters)
+
+    # string key throws
+    assert_raises(SyntaxError) { create_variable(%(n | pluralize: 'comment': 'comments')) }
   end
 
   def test_output_raw_source_of_variable
@@ -151,7 +163,7 @@ class VariableUnitTest < Minitest::Test
   end
 
   def test_variable_lookup_interface
-    lookup = VariableLookup.new('a.b.c')
+    lookup = VariableLookup.parse('a.b.c')
     assert_equal('a', lookup.name)
     assert_equal(['b', 'c'], lookup.lookups)
   end