Merge pull request #1086 from Shopify/liquid-tag

Add {% liquid %} and {% echo %} tags

lib/liquid/block_body.rb

@@ -1,6 +1,7 @@
 module Liquid
   class BlockBody
-    FullToken = /\A#{TagStart}#{WhitespaceControl}?\s*(\w+)\s*(.*?)#{WhitespaceControl}?#{TagEnd}\z/om
+    LiquidTagToken = /\A\s*(\w+)\s*(.*?)\z/o
+    FullToken = /\A#{TagStart}#{WhitespaceControl}?(\s*)(\w+)(\s*)(.*?)#{WhitespaceControl}?#{TagEnd}\z/om
     ContentOfVariable = /\A#{VariableStart}#{WhitespaceControl}?(.*?)#{WhitespaceControl}?#{VariableEnd}\z/om
     WhitespaceOrNothing = /\A\s*\z/
     TAGSTART = "{%".freeze
@@ -13,8 +14,42 @@ module Liquid
       @blank = true
     end
 
-    def parse(tokenizer, parse_context)
+    def parse(tokenizer, parse_context, &block)
       parse_context.line_number = tokenizer.line_number
+
+      if tokenizer.for_liquid_tag
+        parse_for_liquid_tag(tokenizer, parse_context, &block)
+      else
+        parse_for_document(tokenizer, parse_context, &block)
+      end
+    end
+
+    private def parse_for_liquid_tag(tokenizer, parse_context)
+      while token = tokenizer.shift
+        unless token.empty? || token =~ WhitespaceOrNothing
+          unless token =~ LiquidTagToken
+            # line isn't empty but didn't match tag syntax, yield and let the
+            # caller raise a syntax error
+            return yield token, token
+          end
+          tag_name = $1
+          markup = $2
+          unless tag = registered_tags[tag_name]
+            # end parsing if we reach an unknown tag and let the caller decide
+            # determine how to proceed
+            return yield tag_name, markup
+          end
+          new_tag = tag.parse(tag_name, markup, tokenizer, parse_context)
+          @blank &&= new_tag.blank?
+          @nodelist << new_tag
+        end
+        parse_context.line_number = tokenizer.line_number
+      end
+
+      yield nil, nil
+    end
+
+    private def parse_for_document(tokenizer, parse_context, &block)
       while token = tokenizer.shift
         next if token.empty?
         case
@@ -23,9 +58,20 @@ module Liquid
           unless token =~ FullToken
             raise_missing_tag_terminator(token, parse_context)
           end
-          tag_name = $1
-          markup = $2
-          # fetch the tag from registered blocks
+          tag_name = $2
+          markup = $4
+
+          if parse_context.line_number
+            # newlines inside the tag should increase the line number,
+            # particularly important for multiline {% liquid %} tags
+            parse_context.line_number += $1.count("\n".freeze) + $3.count("\n".freeze)
+          end
+
+          if tag_name == 'liquid'.freeze
+            liquid_tag_tokenizer = Tokenizer.new(markup, line_number: parse_context.line_number, for_liquid_tag: true)
+            next parse_for_liquid_tag(liquid_tag_tokenizer, parse_context, &block)
+          end
+
           unless tag = registered_tags[tag_name]
             # end parsing if we reach an unknown tag and let the caller decide
             # determine how to proceed

lib/liquid/tag.rb

@@ -5,8 +5,8 @@ module Liquid
     include ParserSwitching
 
     class << self
-      def parse(tag_name, markup, tokenizer, options)
-        tag = new(tag_name, markup, options)
+      def parse(tag_name, markup, tokenizer, parse_context)
+        tag = new(tag_name, markup, parse_context)
         tag.parse(tokenizer)
         tag
       end

lib/liquid/tags/assign.rb

@@ -10,6 +10,10 @@ module Liquid
   class Assign < Tag
     Syntax = /(#{VariableSignature}+)\s*=\s*(.*)\s*/om
 
+    def self.syntax_error_translation_key
+      "errors.syntax.assign".freeze
+    end
+
     attr_reader :to, :from
 
     def initialize(tag_name, markup, options)
@@ -18,7 +22,7 @@ module Liquid
         @to = $1
         @from = Variable.new($2, options)
       else
-        raise SyntaxError.new options[:locale].t("errors.syntax.assign".freeze)
+        raise SyntaxError.new(options[:locale].t(self.class.syntax_error_translation_key))
       end
     end
 

lib/liquid/tags/echo.rb

@@ -0,0 +1,24 @@
+module Liquid
+  # Echo outputs an expression
+  #
+  #   {% echo monkey %}
+  #   {% echo user.name %}
+  #
+  # This is identical to variable output syntax, like {{ foo }}, but works
+  # inside {% liquid %} tags. The full syntax is supported, including filters:
+  #
+  #   {% echo user | link %}
+  #
+  class Echo < Tag
+    def initialize(tag_name, markup, parse_context)
+      super
+      @variable = Variable.new(markup, parse_context)
+    end
+
+    def render(context)
+      @variable.render(context)
+    end
+  end
+
+  Template.register_tag('echo'.freeze, Echo)
+end

lib/liquid/tokenizer.rb

@@ -1,25 +1,31 @@
 module Liquid
   class Tokenizer
-    attr_reader :line_number
+    attr_reader :line_number, :for_liquid_tag
 
-    def initialize(source, line_numbers = false)
+    def initialize(source, line_numbers = false, line_number: nil, for_liquid_tag: false)
       @source = source
-      @line_number = line_numbers ? 1 : nil
+      @line_number = line_number || (line_numbers ? 1 : nil)
+      @for_liquid_tag = for_liquid_tag
       @tokens = tokenize
     end
 
     def shift
-      token = @tokens.shift
-      @line_number += token.count("\n") if @line_number && token
+      token = @tokens.shift or return
+
+      if @line_number
+        @line_number += @for_liquid_tag ? 1 : token.count("\n")
+      end
+
       token
     end
 
     private
 
     def tokenize
-      @source = @source.source if @source.respond_to?(:source)
       return [] if @source.to_s.empty?
 
+      return @source.split("\n") if @for_liquid_tag
+
       tokens = @source.split(TemplateParser)
 
       # removes the rogue empty element at the beginning of the array