add content_for tag

Author: chamnap

README.md

@@ -76,7 +76,8 @@ Currently, **Liquid-Rails** adds only the followings:
 1. [csrf_meta_tags](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/csrf_meta_tags.rb)
 2. [google_analytics_tag](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/google_analytics_tag.rb)
 3. [javascript_tag](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/javascript_tag.rb)
-4. [paginate_tag](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/paginate_tag.rb)
+4. [paginate](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/paginate_tag.rb)
+4. [content_for](https://github.com/yoolk/liquid-rails/blob/master/lib/liquid-rails/tags/content_for.rb)
 
 ### Drop Class
 

lib/liquid-rails/rspec/drop_example_group.rb

@@ -17,10 +17,8 @@ module DropExampleGroup
             end
           }
 
-          before {
-            setup_view_and_controller
-            subject.context = context
-          }
+          before(:all)  { setup_view_and_controller }
+          before(:each) { subject.context = context }
         end
       end
     end

lib/liquid-rails/rspec/tag_example_group.rb

@@ -12,7 +12,12 @@ module TagExampleGroup
         end
 
         def expect_template_result(template, expected, assigns={})
-          actual = Liquid::Template.parse(template).render!(assigns, { registers: { helper: @view, view: @view, controller: @controller } })
+          # make assigns available inside context
+          assigns.each do |key, value|
+            context[key] = value
+          end
+
+          actual = Liquid::Template.parse(template).render!(context)
           expect(actual).to eq(expected)
         end
       end

lib/liquid-rails/tags/content_for_tag.rb

@@ -0,0 +1,68 @@
+# It works similar to Rails #content_for.
+# Calling #content_for stores a block of markup in an identifier for later use.
+# In order to access this stored content in other templates or the layout, you would pass the identifier as an argument to content_for.
+#
+# Usage:
+#
+# {% content_for :not_authorized %}
+#   alert('You are not authorized to do that!');
+# {% endcontent_for %}
+#
+# You can then use content_for :not_authorized anywhere in your templates.
+# {% if current_user.nil? %}
+#   {% yield :not_authorized %}
+# {% endif %}
+
+module Liquid
+  module Rails
+    class ContentForTag < ::Liquid::Block
+      Syntax = /(#{::Liquid::QuotedFragment})\s*(flush\s*(true|false))?/
+
+      def initialize(tag_name, markup, context)
+        super
+
+        if markup =~ Syntax
+          @identifier = $1.to_s
+          @flush = $3
+        else
+          raise SyntaxError.new("Syntax Error - Valid syntax: {% content_for [name] %}")
+        end
+      end
+
+      def render(context)
+        @context = context
+
+        options = @flush == 'true' ? { flush: true } : {}
+        @context.registers[:view].content_for(@identifier, super.html_safe, options)
+        ''
+      end
+    end
+  end
+end
+
+module Liquid
+  module Rails
+    class YieldTag < ::Liquid::Tag
+      Syntax = /(#{::Liquid::QuotedFragment})/
+
+      def initialize(tag_name, markup, context)
+        super
+
+        if markup =~ Syntax
+          @identifier = $1
+        else
+          raise SyntaxError.new("Syntax Error - Valid syntax: {% yield [name] %}")
+        end
+      end
+
+      def render(context)
+        @context = context
+
+        @context.registers[:view].content_for(@identifier).try(:html_safe)
+      end
+    end
+  end
+end
+
+Liquid::Template.register_tag('content_for', Liquid::Rails::ContentForTag)
+Liquid::Template.register_tag('yield', Liquid::Rails::YieldTag)

lib/liquid-rails/tags/google_analytics_tag.rb

@@ -7,7 +7,6 @@
 module Liquid
   module Rails
     class GoogleAnalyticsTag < ::Liquid::Tag
-
       Syntax = /(#{::Liquid::QuotedFragment}+)?/
 
       def initialize(tag_name, markup, tokens)

spec/lib/liquid-rails/tags/content_for_tag_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+
+module Liquid
+  module Rails
+    describe ContentForTag, type: :tag do
+      it 'content_for and yield' do
+        Liquid::Template.parse(%|{% content_for not_authorized1 %}alert('You are not authorized to do that!');{% endcontent_for %}|).render(context)
+
+        expect_template_result(%|{% yield not_authorized1 %}|, "alert('You are not authorized to do that!');")
+      end
+
+      it 'invokes content_for with the same identifier multiple times' do
+        Liquid::Template.parse(%|{% content_for not_authorized2 %}alert('You are not authorized to do that 1!');{% endcontent_for %}|).render(context)
+        Liquid::Template.parse(%|{% content_for not_authorized2 %}alert('You are not authorized to do that 2!');{% endcontent_for %}|).render(context)
+
+        expect_template_result(%|{% yield not_authorized2 %}|, "alert('You are not authorized to do that 1!');alert('You are not authorized to do that 2!');")
+      end
+
+      it 'invokes content_for with the same identifier multiple times and flush' do
+        Liquid::Template.parse(%|{% content_for not_authorized3 %}alert('You are not authorized to do that 1!');{% endcontent_for %}|).render(context)
+        Liquid::Template.parse(%|{% content_for not_authorized3 flush true %}alert('You are not authorized to do that 2!');{% endcontent_for %}|).render(context)
+
+        expect_template_result(%|{% yield not_authorized3 %}|, "alert('You are not authorized to do that 2!');")
+      end
+    end
+  end
+end