Implement multi-line suggestions filtering

Implements the filtering logic for
`suggestion:-x+y` syntax.

4 files changed, 49 insertions, 6 deletions

diff --git a/lib/banzai/filter/output_safety.rb b/lib/banzai/filter/output_safety.rb
new file mode 100644
index 00000000000..d4ebce5d9c9
--- /dev/null
+++ b/lib/banzai/filter/output_safety.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    module OutputSafety
+      def escape_once(html)
+        html.html_safe? ? html : ERB::Util.html_escape_once(html)
+      end
+    end
+  end
+end
diff --git a/lib/banzai/filter/reference_filter.rb b/lib/banzai/filter/reference_filter.rb
index 42f9b3a689c..b3ce9200b49 100644
--- a/lib/banzai/filter/reference_filter.rb
+++ b/lib/banzai/filter/reference_filter.rb
@@ -12,6 +12,7 @@ module Banzai
     #   :only_path          - Generate path-only links.
     class ReferenceFilter < HTML::Pipeline::Filter
       include RequestStoreReferenceCache
+      include OutputSafety
 
       class << self
         attr_accessor :reference_type
@@ -43,10 +44,6 @@ module Banzai
         end.join(' ')
       end
 
-      def escape_once(html)
-        html.html_safe? ? html : ERB::Util.html_escape_once(html)
-      end
-
       def ignore_ancestor_query
         @ignore_ancestor_query ||= begin
           parents = %w(pre code a style)
diff --git a/lib/banzai/filter/suggestion_filter.rb b/lib/banzai/filter/suggestion_filter.rb
index 9950db373d8..848aca10a20 100644
--- a/lib/banzai/filter/suggestion_filter.rb
+++ b/lib/banzai/filter/suggestion_filter.rb
@@ -6,11 +6,15 @@ module Banzai
     class SuggestionFilter < HTML::Pipeline::Filter
       # Class used for tagging elements that should be rendered
       TAG_CLASS = 'js-render-suggestion'.freeze
+      SUGGESTION_REGEX = Gitlab::Diff::SuggestionsParser::SUGGESTION_CONTEXT
 
       def call
         return doc unless suggestions_filter_enabled?
 
         doc.search('pre.suggestion > code').each do |node|
+          # TODO: Remove once multi-line suggestions FF get removed (#59178).
+          remove_multi_line_params(node.parent)
+
           node.add_class(TAG_CLASS)
         end
 
@@ -20,6 +24,20 @@ module Banzai
       def suggestions_filter_enabled?
         context[:suggestions_filter_enabled]
       end
+
+      private
+
+      def project
+        context[:project]
+      end
+
+      def remove_multi_line_params(node)
+        return if Feature.enabled?(:multi_line_suggestions, project)
+
+        if node[SyntaxHighlightFilter::LANG_PARAMS_ATTR]&.match?(SUGGESTION_REGEX)
+          node.remove_attribute(SyntaxHighlightFilter::LANG_PARAMS_ATTR)
+        end
+      end
     end
   end
 end
diff --git a/lib/banzai/filter/syntax_highlight_filter.rb b/lib/banzai/filter/syntax_highlight_filter.rb
index 9ffde52b5f2..fe56f9a1e33 100644
--- a/lib/banzai/filter/syntax_highlight_filter.rb
+++ b/lib/banzai/filter/syntax_highlight_filter.rb
@@ -8,6 +8,11 @@ module Banzai
     # HTML Filter to highlight fenced code blocks
     #
     class SyntaxHighlightFilter < HTML::Pipeline::Filter
+      include OutputSafety
+
+      PARAMS_DELIMITER = ':'.freeze
+      LANG_PARAMS_ATTR = 'data-lang-params'.freeze
+
       def call
         doc.search('pre > code').each do |node|
           highlight_node(node)
@@ -18,7 +23,7 @@ module Banzai
 
       def highlight_node(node)
         css_classes = +'code highlight js-syntax-highlight'
-        lang = node.attr('lang')
+        lang, lang_params = parse_lang_params(node.attr('lang'))
         retried = false
 
         if use_rouge?(lang)
@@ -46,7 +51,10 @@ module Banzai
           retry
         end
 
-        highlighted = %(<pre class="#{css_classes}" lang="#{language}" v-pre="true"><code>#{code}</code></pre>)
+        highlighted = %(<pre class="#{css_classes}"
+                             lang="#{language}"
+                             #{lang_params}
+                             v-pre="true"><code>#{code}</code></pre>)
 
         # Extracted to a method to measure it
         replace_parent_pre_element(node, highlighted)
@@ -54,6 +62,15 @@ module Banzai
 
       private
 
+      def parse_lang_params(language)
+        return unless language
+
+        lang, params = language.split(PARAMS_DELIMITER, 2)
+        formatted_params = %(#{LANG_PARAMS_ATTR}="#{escape_once(params)}") if params
+
+        [lang, formatted_params]
+      end
+
       # Separate method so it can be instrumented.
       def lex(lexer, code)
         lexer.lex(code)