Enable wiki table of contents tag for GFM

`[[_TOC_]]` now gets converted for normal GDM markdown

changelogs/unreleased/21901-support-for-toc-in-readme-files.yml

+---
+title: Support for table of contents tag in GitLab Flavored Markdown
+merge_request: 24196
+author:
+type: added

lib/banzai/filter/gollum_tags_filter.rb

@@ -25,12 +25,10 @@ module Banzai
     #   * [[http://example.com/images/logo.png]]
     #   * [[http://example.com/images/logo.png|alt=Logo]]
     #
-    # - Insert a Table of Contents list:
-    #
-    #   * [[_TOC_]]
-    #
     # Based on Gollum::Filter::Tags
     #
+    # Note: the table of contents tag is now handled by TableOfContentsTagFilter
+    #
     # Context options:
     #   :project_wiki (required) - Current project wiki.
     #
@@ -64,23 +62,11 @@ module Banzai
       def call
         doc.search(".//text()").each do |node|
           next if has_ancestor?(node, IGNORED_ANCESTOR_TAGS)
-
-          # A Gollum ToC tag is `[[_TOC_]]`, but due to MarkdownFilter running
-          # before this one, it will be converted into `[[<em>TOC</em>]]`, so it
-          # needs special-case handling
-          if toc_tag?(node)
-            process_toc_tag(node)
-          else
-            content = node.content
-
-            next unless content =~ TAGS_PATTERN
+          next unless node.content =~ TAGS_PATTERN
 
           html = process_tag($1)
 
-            if html && html != node.content
-              node.replace(html)
-            end
-          end
+          node.replace(html) if html && html != node.content
         end
 
         doc
@@ -88,12 +74,6 @@ module Banzai
 
       private
 
-      # Replace an entire `[[<em>TOC</em>]]` node with the result generated by
-      # TableOfContentsFilter
-      def process_toc_tag(node)
-        node.parent.parent.replace(result[:toc].presence || '')
-      end
-
       # Process a single tag into its final HTML form.
       #
       # tag - The String tag contents (the stuff inside the double brackets).
@@ -129,12 +109,6 @@ module Banzai
         end
       end
 
-      def toc_tag?(node)
-        node.content == 'TOC' &&
-          node.parent.name == 'em' &&
-          node.parent.parent.text == '[[TOC]]'
-      end
-
       def image?(path)
         path =~ ALLOWED_IMAGE_EXTENSIONS
       end

lib/banzai/filter/table_of_contents_tag_filter.rb

+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # Using `[[_TOC_]]`, inserts a Table of Contents list.
+    # This syntax is based on the Gollum syntax. This way we have
+    # some consistency between with wiki and normal markdown.
+    # If there ever emerges a markdown standard, we can implement
+    # that here.
+    #
+    # The support for this has been removed from GollumTagsFilter
+    #
+    # Based on Banzai::Filter::GollumTagsFilter
+    class TableOfContentsTagFilter < HTML::Pipeline::Filter
+      TEXT_QUERY = %q(descendant-or-self::text()[ancestor::p and contains(., 'TOC')])
+
+      def call
+        return doc if context[:no_header_anchors]
+
+        doc.xpath(TEXT_QUERY).each do |node|
+          # A Gollum ToC tag is `[[_TOC_]]`, but due to MarkdownFilter running
+          # before this one, it will be converted into `[[<em>TOC</em>]]`, so it
+          # needs special-case handling
+          process_toc_tag(node) if toc_tag?(node)
+        end
+
+        doc
+      end
+
+      private
+
+      # Replace an entire `[[<em>TOC</em>]]` node with the result generated by
+      # TableOfContentsFilter
+      def process_toc_tag(node)
+        node.parent.parent.replace(result[:toc].presence || '')
+      end
+
+      def toc_tag?(node)
+        node.content == 'TOC' &&
+          node.parent.name == 'em' &&
+          node.parent.parent.text == '[[TOC]]'
+      end
+    end
+  end
+end

lib/banzai/pipeline/gfm_pipeline.rb

@@ -32,6 +32,7 @@ module Banzai
           Filter::InlineMetricsFilter,
           Filter::InlineGrafanaMetricsFilter,
           Filter::TableOfContentsFilter,
+          Filter::TableOfContentsTagFilter,
           Filter::AutolinkFilter,
           Filter::ExternalLinkFilter,
           Filter::SuggestionFilter,

spec/lib/banzai/filter/gollum_tags_filter_spec.rb

@@ -100,19 +100,4 @@ describe Banzai::Filter::GollumTagsFilter do
       expect(doc.at_css('code').text).to eq '[[link-in-backticks]]'
     end
   end
-
-  context 'table of contents' do
-    it 'replaces [[<em>TOC</em>]] with ToC result' do
-      doc = described_class.call("<p>[[<em>TOC</em>]]</p>", { project_wiki: project_wiki }, { toc: "FOO" })
-
-      expect(doc.to_html).to eq("FOO")
-    end
-
-    it 'handles an empty ToC result' do
-      input = "<p>[[<em>TOC</em>]]</p>"
-      doc = described_class.call(input, project_wiki: project_wiki)
-
-      expect(doc.to_html).to eq ''
-    end
-  end
 end

spec/lib/banzai/filter/table_of_contents_tag_filter_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Banzai::Filter::TableOfContentsTagFilter do
+  include FilterSpecHelper
+
+  context 'table of contents' do
+    let(:html) { '<p>[[<em>TOC</em>]]</p>' }
+
+    it 'replaces [[<em>TOC</em>]] with ToC result' do
+      doc = filter(html, {}, { toc: "FOO" })
+
+      expect(doc.to_html).to eq("FOO")
+    end
+
+    it 'handles an empty ToC result' do
+      doc = filter(html)
+
+      expect(doc.to_html).to eq ''
+    end
+  end
+end

spec/lib/banzai/pipeline/full_pipeline_spec.rb

@@ -99,4 +99,35 @@ describe Banzai::Pipeline::FullPipeline do
       end
     end
   end
+
+  describe 'table of contents' do
+    let(:project) { create(:project, :public) }
+    let(:markdown) do
+      <<-MARKDOWN.strip_heredoc
+          [[_TOC_]]
+
+          # Header
+      MARKDOWN
+    end
+    let(:invalid_markdown) do
+      <<-MARKDOWN.strip_heredoc
+          test [[_TOC_]]
+
+          # Header
+      MARKDOWN
+    end
+
+    it 'inserts a table of contents' do
+      output = described_class.to_html(markdown, project: project)
+
+      expect(output).to include("<ul class=\"section-nav\">")
+      expect(output).to include("<li><a href=\"#header\">Header</a></li>")
+    end
+
+    it 'does not insert a table of contents' do
+      output = described_class.to_html(invalid_markdown, project: project)
+
+      expect(output).to include("test [[<em>TOC</em>]]")
+    end
+  end
 end

spec/support/helpers/filter_spec_helper.rb

@@ -15,7 +15,7 @@ module FilterSpecHelper
   # context - Hash context for the filter. (default: {project: project})
   #
   # Returns a Nokogiri::XML::DocumentFragment
-  def filter(html, context = {})
+  def filter(html, context = {}, result = nil)
     if defined?(project)
       context.reverse_merge!(project: project)
     end
@@ -25,7 +25,7 @@ module FilterSpecHelper
 
     context = context.merge(render_context: render_context)
 
-    described_class.call(html, context)
+    described_class.call(html, context, result)
   end
 
   # Get an instance of the Filter class