Allow suggesting single line changes in diffs

5 files changed, 43 insertions, 2 deletions

diff --git a/lib/banzai/filter/suggestion_filter.rb b/lib/banzai/filter/suggestion_filter.rb
new file mode 100644
index 00000000000..822db7cf26e
--- /dev/null
+++ b/lib/banzai/filter/suggestion_filter.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    class SuggestionFilter < HTML::Pipeline::Filter
+      # Class used for tagging elements that should be rendered
+      TAG_CLASS = 'js-render-suggestion'.freeze
+
+      def call
+        return doc unless Suggestion.feature_enabled?
+        return doc unless suggestions_filter_enabled?
+
+        doc.search('pre.suggestion > code').each do |node|
+          node.add_class(TAG_CLASS)
+        end
+
+        doc
+      end
+
+      def suggestions_filter_enabled?
+        context[:suggestions_filter_enabled]
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/syntax_highlight_filter.rb b/lib/banzai/filter/syntax_highlight_filter.rb
index 8a7f9045c24..18e5e9185de 100644
--- a/lib/banzai/filter/syntax_highlight_filter.rb
+++ b/lib/banzai/filter/syntax_highlight_filter.rb
@@ -69,7 +69,7 @@ module Banzai
       end
 
       def use_rouge?(language)
-        %w(math mermaid plantuml).exclude?(language)
+        %w(math mermaid plantuml suggestion).exclude?(language)
       end
     end
   end
diff --git a/lib/banzai/pipeline/gfm_pipeline.rb b/lib/banzai/pipeline/gfm_pipeline.rb
index 96bea7ca935..5f13a6d6cde 100644
--- a/lib/banzai/pipeline/gfm_pipeline.rb
+++ b/lib/banzai/pipeline/gfm_pipeline.rb
@@ -29,6 +29,7 @@ module Banzai
           Filter::TableOfContentsFilter,
           Filter::AutolinkFilter,
           Filter::ExternalLinkFilter,
+          Filter::SuggestionFilter,
 
           *reference_filters,
 
diff --git a/lib/banzai/pipeline/post_process_pipeline.rb b/lib/banzai/pipeline/post_process_pipeline.rb
index 63a998a2c1f..7eaad6d7560 100644
--- a/lib/banzai/pipeline/post_process_pipeline.rb
+++ b/lib/banzai/pipeline/post_process_pipeline.rb
@@ -14,7 +14,8 @@ module Banzai
         [
           Filter::RedactorFilter,
           Filter::RelativeLinkFilter,
-          Filter::IssuableStateFilter
+          Filter::IssuableStateFilter,
+          Filter::SuggestionFilter
         ]
       end
 
diff --git a/lib/banzai/suggestions_parser.rb b/lib/banzai/suggestions_parser.rb
new file mode 100644
index 00000000000..09f36635020
--- /dev/null
+++ b/lib/banzai/suggestions_parser.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Banzai
+  module SuggestionsParser
+    # Returns the content of each suggestion code block.
+    #
+    def self.parse(text)
+      html = Banzai.render(text, project: nil, no_original_data: true)
+      doc = Nokogiri::HTML(html)
+
+      doc.search('pre.suggestion').map { |node| node.text }
+    end
+  end
+end