added feature flag 'commonmark_for_repositories'

app/helpers/markup_helper.rb

@@ -107,6 +107,7 @@ module MarkupHelper
 
   def markup(file_name, text, context = {})
     context[:project] ||= @project
+    context[:markdown_engine] ||= :redcarpet unless commonmark_for_repositories_enabled?
     html = context.delete(:rendered) || markup_unsafe(file_name, text, context)
     prepare_for_rendering(html, context)
   end
@@ -122,6 +123,7 @@ module MarkupHelper
       page_slug: wiki_page.slug,
       issuable_state_filter_enabled: true
     )
+    context[:markdown_engine] ||= :redcarpet unless commonmark_for_repositories_enabled?
 
     html =
       case wiki_page.format
@@ -176,6 +178,10 @@ module MarkupHelper
     end
   end
 
+  def commonmark_for_repositories_enabled?
+    Feature.enabled?(:commonmark_for_repositories, default_enabled: true)
+  end
+
   private
 
   # Return +text+, truncated to +max_chars+ characters, excluding any HTML

app/models/repository.rb

@@ -580,7 +580,12 @@ class Repository
   end
 
   def rendered_readme
-    MarkupHelper.markup_unsafe(readme.name, readme.data, project: project) if readme
+    return unless readme
+
+    context = { project: project }
+    context[:markdown_engine] = :redcarpet unless MarkupHelper.commonmark_for_repositories_enabled?
+
+    MarkupHelper.markup_unsafe(readme.name, readme.data, context)
   end
   cache_method :rendered_readme
 

app/views/projects/wikis/_form.html.haml

 - commit_message = @page.persisted? ? s_("WikiPageEdit|Update %{page_title}") : s_("WikiPageCreate|Create %{page_title}")
 - commit_message = commit_message % { page_title: @page.title }
-- markdown_version = params[:legacy_render] ? CacheMarkdownField::CACHE_REDCARPET_VERSION : 0
+- if params[:legacy_render] || !commonmark_for_repositories_enabled?
+  - markdown_version = CacheMarkdownField::CACHE_REDCARPET_VERSION
+- else
+  - markdown_version = 0
 
 = form_for [@project.namespace.becomes(Namespace), @project, @page], method: @page.persisted? ? :put : :post,
            html: { class: 'wiki-form common-note-form prepend-top-default js-quick-submit' },

spec/helpers/markup_helper_spec.rb

@@ -212,6 +212,17 @@ describe MarkupHelper do
       helper.render_wiki_content(@wiki)
     end
 
+    it 'uses Wiki pipeline for markdown files with RedCarpet if feature disabled' do
+      stub_feature_flags(commonmark_for_repositories: false)
+      allow(@wiki).to receive(:format).and_return(:markdown)
+
+      expect(helper).to receive(:markdown_unsafe).with('wiki content',
+        pipeline: :wiki, project: project, project_wiki: @wiki, page_slug: "nested/page",
+        issuable_state_filter_enabled: true, markdown_engine: :redcarpet)
+
+      helper.render_wiki_content(@wiki)
+    end
+
     it "uses Asciidoctor for asciidoc files" do
       allow(@wiki).to receive(:format).and_return(:asciidoc)
 
@@ -266,6 +277,12 @@ describe MarkupHelper do
     it 'honors markdown_engine for RedCarpet' do
       expect(helper.markup('foo.md', 'x^2', { markdown_engine: :redcarpet })).to include('x<sup>2</sup>')
     end
+
+    it 'uses RedCarpet if feature disabled' do
+      stub_feature_flags(commonmark_for_repositories: false)
+
+      expect(helper.markup('foo.md', 'x^2', { markdown_engine: :redcarpet })).to include('x<sup>2</sup>')
+    end
   end
 
   describe '#first_line_in_markdown' do