Disable rendering of tag based on register (#1162)

* Disable rendering of tag based on register

* Improvements to disable tag

* Resolve disbale tag tests

* Test disable_tags register

* disabled_tags is now always avaiable

* Allow multiple tags to be disabled at once

* Move disabled check to block_body

* Code improvements

* Remove redundant nil check

* Improve disabled tag error output

* Improve disable tag API

* Code improvements

* Switch disabled? to not mutate output

* Fix array handling shortcut in disable_tags

lib/liquid.rb

@@ -78,8 +78,10 @@ require 'liquid/tokenizer'
 require 'liquid/parse_context'
 require 'liquid/partial_cache'
 require 'liquid/usage'
+require 'liquid/register'
 require 'liquid/static_registers'
 
 # Load all the tags of the standard library
 #
 Dir["#{__dir__}/liquid/tags/*.rb"].each { |f| require f }
+Dir["#{__dir__}/liquid/registers/*.rb"].each { |f| require f }

lib/liquid/block_body.rb

@@ -154,7 +154,13 @@ module Liquid
     private
 
     def render_node(context, output, node)
-      node.render_to_output_buffer(context, output)
+      if node.disabled?(context)
+        output << node.disabled_error_message
+        return
+      end
+      disable_tags(context, node.disabled_tags) do
+        node.render_to_output_buffer(context, output)
+      end
     rescue UndefinedVariable, UndefinedDropMethod, UndefinedFilter => e
       context.handle_error(e, node.line_number)
     rescue ::StandardError => e
@@ -162,6 +168,11 @@ module Liquid
       output << context.handle_error(e, line_number)
     end
 
+    def disable_tags(context, tags, &block)
+      return yield if tags.empty?
+      context.registers['disabled_tags'].disable(tags, &block)
+    end
+
     def raise_if_resource_limits_reached(context, length)
       context.resource_limits.render_length += length
       return unless context.resource_limits.reached?

lib/liquid/locales/en.yml

@@ -25,3 +25,5 @@
       render: "Syntax error in tag 'render' - Template name must be a quoted string"
     argument:
       include: "Argument error in tag 'include' - Illegal template name"
+    disabled:
+      tag: "usage is not allowed in this context"

lib/liquid/register.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module Liquid
+  class Register
+  end
+end

lib/liquid/registers/disabled_tags.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+module Liquid
+  class DisabledTags < Register
+    def initialize
+      @disabled_tags = {}
+    end
+
+    def disabled?(tag)
+      @disabled_tags.key?(tag) && @disabled_tags[tag] > 0
+    end
+
+    def disable(tags)
+      tags.each(&method(:increment))
+      yield
+    ensure
+      tags.each(&method(:decrement))
+    end
+
+    private
+
+    def increment(tag)
+      @disabled_tags[tag] ||= 0
+      @disabled_tags[tag] += 1
+    end
+
+    def decrement(tag)
+      @disabled_tags[tag] -= 1
+    end
+  end
+
+  Template.add_register('disabled_tags', DisabledTags.new)
+end

lib/liquid/tag.rb

@@ -13,7 +13,15 @@ module Liquid
         tag
       end
 
+      def disable_tags(*tags)
+        disabled_tags.push(*tags)
+      end
+
       private :new
+
+      def disabled_tags
+        @disabled_tags ||= []
+      end
     end
 
     def initialize(tag_name, markup, parse_context)
@@ -38,6 +46,14 @@ module Liquid
       ''
     end
 
+    def disabled?(context)
+      context.registers['disabled_tags'].disabled?(tag_name)
+    end
+
+    def disabled_error_message
+      "#{tag_name} #{options[:locale].t('errors.disabled.tag')}"
+    end
+
     # For backwards compatibility with custom tags. In a future release, the semantics
     # of the `render_to_output_buffer` method will become the default and the `render`
     # method will be removed.
@@ -49,5 +65,9 @@ module Liquid
     def blank?
       false
     end
+
+    def disabled_tags
+      self.class.disabled_tags
+    end
   end
 end

lib/liquid/tags/render.rb

@@ -4,6 +4,8 @@ module Liquid
   class Render < Tag
     SYNTAX = /(#{QuotedString})#{QuotedFragment}*/o
 
+    disable_tags "include"
+
     attr_reader :template_name_expr, :attributes
 
     def initialize(tag_name, markup, options)
@@ -22,6 +24,10 @@ module Liquid
     end
 
     def render_to_output_buffer(context, output)
+      render_tag(context, output)
+    end
+
+    def render_tag(context, output)
       # Though we evaluate this here we will only ever parse it as a string literal.
       template_name = context.evaluate(@template_name_expr)
       raise ArgumentError, options[:locale].t("errors.argument.include") unless template_name

lib/liquid/template.rb

@@ -92,6 +92,14 @@ module Liquid
         @tags ||= TagRegistry.new
       end
 
+      def add_register(name, klass)
+        registers[name.to_s] = klass
+      end
+
+      def registers
+        @registers ||= {}
+      end
+
       def error_mode
         @error_mode ||= :lax
       end
@@ -191,18 +199,26 @@ module Liquid
 
       output = nil
 
+      context_register = context.registers.is_a?(StaticRegisters) ? context.registers.static : context.registers
+
       case args.last
       when Hash
         options = args.pop
         output = options[:output] if options[:output]
 
-        registers.merge!(options[:registers]) if options[:registers].is_a?(Hash)
+        options[:registers]&.each do |key, register|
+          context_register[key] = register
+        end
 
         apply_options_to_context(context, options)
       when Module, Array
         context.add_filters(args.pop)
       end
 
+      Template.registers.each do |key, register|
+        context_register[key] = register
+      end
+
       # Retrying a render resets resource usage
       context.resource_limits.reset
 

lib/liquid/variable.rb

@@ -104,6 +104,14 @@ module Liquid
       output
     end
 
+    def disabled?(_context)
+      false
+    end
+
+    def disabled_tags
+      []
+    end
+
     private
 
     def parse_filter_expressions(filter_name, unparsed_args)