Refactor `highlight` tag to behave like the `raw` tag (#6821)

Merge pull request 6821

features/highlighting.feature

@@ -31,3 +31,47 @@ Feature: Syntax Highlighting
     When I run jekyll build
     Then I should get a zero exit-status
     And I should see "<span class="nc">RewriteCond</span>" in "_site/index.html"
+
+  Scenario: highlighting an Liquid example
+    Given I have an "inspect.md" file with content:
+    """
+    ---
+    title: Inspect Filter
+    ---
+    You can inspect a page's attributes with the `inspect` filter. You may enclose the
+    entire introspection within `<pre></pre>` tags to preserve the formatting:
+    {% highlight html %}
+    <pre id="inspect-filter">
+      {{ page | inspect }}
+    </pre>
+    {% endhighlight %}
+    """
+    When I run jekyll build
+    Then I should get a zero exit-status
+    And I should see "<code class=\"language-html\" data-lang=\"html\">" in "_site/inspect.html"
+    And I should see "{{ page | inspect }}" in "_site/inspect.html"
+
+  Scenario: highlighting an included snippet
+    Given I have an _includes directory
+    And I have an "_includes/inspector.html" file with content:
+    """
+    <pre id="inspect-filter">
+      {{ page | inspect }}
+    </pre>
+    """
+    And I have an "inspect.md" file with content:
+    """
+    ---
+    title: Inspect Filter
+    ---
+    You can inspect a page's attributes with the `inspect` filter. You may enclose the
+    entire introspection within `<pre></pre>` tags to preserve the formatting:
+    {% highlight html %}
+      {% include inspector.html %}
+    {% endhighlight %}
+    """
+    When I run jekyll build
+    Then I should get a zero exit-status
+    And I should see "<code class=\"language-html\" data-lang=\"html\">" in "_site/inspect.html"
+    But I should not see "{{ page | inspect }}" in "_site/inspect.html"
+    But I should see "{% include inspector.html %}" in "_site/inspect.html"

jekyll.gemspec

@@ -52,6 +52,13 @@ Gem::Specification.new do |s|
       * Our `link` tag now comes with the `relative_url` filter incorporated into it.
         You should no longer prepend `{{ site.baseurl }}` to `{% link foo.md %}`
         For further details: https://github.com/jekyll/jekyll/pull/6727
+
+      * Our `highlight` tag no longer parses Liquid and Liquid-like constructs in the
+        tag's content body. While this means you no longer need to enclose the content
+        within a `{% raw %}{% endraw %}` block, it also means that you can no longer
+        do the following as well:
+        `{% highlight html %}{% include snippet.html %}{% endhighlight %}`
+        For further details: https://github.com/jekyll/jekyll/pull/6821
     ----------------------------------------------------------------------------------
   MSG
 end

lib/jekyll/tags/highlight.rb

@@ -2,7 +2,7 @@
 
 module Jekyll
   module Tags
-    class HighlightBlock < Liquid::Block
+    class HighlightBlock < Liquid::Raw
       include Liquid::StandardFilters
 
       # The regular expression syntax checker. Start with the language specifier.
@@ -28,10 +28,12 @@ module Jekyll
         end
       end
 
+      LEADING_OR_TRAILING_LINE_TERMINATORS = %r!\A(\n|\r)+|(\n|\r)+\z!.freeze
+
       def render(context)
         prefix = context["highlighter_prefix"] || ""
         suffix = context["highlighter_suffix"] || ""
-        code = super.to_s.gsub(%r!\A(\n|\r)+|(\n|\r)+\z!, "")
+        code   = @body.gsub(LEADING_OR_TRAILING_LINE_TERMINATORS, "")
 
         output =
           case context.registers[:site].highlighter
@@ -101,6 +103,8 @@ module Jekyll
         "<figure class=\"highlight\"><pre><code #{code_attributes}>"\
         "#{code.chomp}</code></pre></figure>"
       end
+
+      def ensure_valid_markup(tag_name, markup, parse_context); end
     end
   end
 end

test/test_tags.rb

@@ -69,6 +69,30 @@ class TestTags < JekyllUnitTest
     end
   end
 
+  context "highlight tag" do
+    setup do
+      create_post <<~CONTENT
+        ---
+        title: This is a test
+        ---
+
+        This is not yet highlighted
+
+        {% highlight html %}
+        <h1>{% unregistered_tag %}</h1>
+        {{ page | inspect }}
+        {% endhighlight %}
+
+        This should not be highlighted, right?
+      CONTENT
+    end
+
+    should "not parse Liquid constructs in the tag markup" do
+      assert_match "{% unregistered_tag %}", @result
+      assert_match "{{ page | inspect }}", @result
+    end
+  end
+
   context "highlight tag in unsafe mode" do
     should "set the no options with just a language name" do
       tag = highlight_block_with_opts("ruby ")