Adds v-pre to code blocks in comments

Closes #22911

CHANGELOG

@@ -14,6 +14,7 @@ v 8.13.0 (unreleased)
   - Simplify Mentionable concern instance methods
   - Fix permission for setting an issue's due date
   - Expose expires_at field when sharing project on API
+  - Fix VueJS template tags being rendered in code comments
   - Fix issue with page scrolling to top when closing or pinning sidebar (lukehowell)
   - Allow the Koding integration to be configured through the API
   - Added soft wrap button to repository file/blob editor
@@ -44,7 +45,7 @@ v 8.13.0 (unreleased)
   - Notify the Merger about merge after successful build (Dimitris Karakasilis)
   - Fix broken repository 500 errors in project list
   - Close todos when accepting merge requests via the API !6486 (tonygambone)
-  - Changed Slack service user referencing from full name to username (Sebastian Poxhofer) 
+  - Changed Slack service user referencing from full name to username (Sebastian Poxhofer)
   - Add Container Registry on/off status to Admin Area !6638 (the-undefined)
 
 v 8.12.4 (unreleased)

lib/banzai/filter/sanitization_filter.rb

@@ -25,7 +25,7 @@ module Banzai
         return if customized?(whitelist[:transformers])
 
         # Allow code highlighting
-        whitelist[:attributes]['pre'] = %w(class)
+        whitelist[:attributes]['pre'] = %w(class v-pre)
         whitelist[:attributes]['span'] = %w(class)
 
         # Allow table alignment

lib/banzai/filter/syntax_highlight_filter.rb

@@ -30,7 +30,8 @@ module Banzai
           # users can still access an issue/comment/etc.
         end
 
-        highlighted = %(<pre class="#{css_classes}"><code>#{code}</code></pre>)
+        highlighted = %(<pre class="#{css_classes}" v-pre="true"><code>#{code}</code></pre>)
+        puts highlighted
 
         # Extracted to a method to measure it
         replace_parent_pre_element(node, highlighted)

spec/features/notes_on_merge_requests_spec.rb

@@ -240,6 +240,18 @@ describe 'Comments', feature: true do
           is_expected.to have_css('.notes_holder .note', count: 1)
           is_expected.to have_button('Reply...')
         end
+
+        it 'adds code to discussion' do
+          click_button 'Reply...'
+
+          page.within(first('.js-discussion-note-form')) do
+            fill_in 'note[note]', with: '```{{ test }}```'
+
+            click_button('Comment')
+          end
+
+          expect(page).to have_content('{{ test }}')
+        end
       end
     end
   end