Fixes multi line comments options in parallel mode

Changes the line number options in parallel mode
to not include the wrong lines.
In parallel mode the dropdown should only include
the line numbers for whichever side the select
option was opened on.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/227159

app/assets/javascripts/diffs/components/diff_line_note_form.vue

@@ -7,7 +7,7 @@ import noteForm from '../../notes/components/note_form.vue';
 import MultilineCommentForm from '../../notes/components/multiline_comment_form.vue';
 import autosave from '../../notes/mixins/autosave';
 import userAvatarLink from '../../vue_shared/components/user_avatar/user_avatar_link.vue';
-import { DIFF_NOTE_TYPE } from '../constants';
+import { DIFF_NOTE_TYPE, PARALLEL_DIFF_VIEW_TYPE } from '../constants';
 import {
   commentLineOptions,
   formatLineRange,
@@ -60,7 +60,7 @@ export default {
       diffViewType: state => state.diffs.diffViewType,
     }),
     ...mapState('diffs', ['showSuggestPopover']),
-    ...mapGetters('diffs', ['getDiffFileByHash']),
+    ...mapGetters('diffs', ['getDiffFileByHash', 'diffLines']),
     ...mapGetters([
       'isLoggedIn',
       'noteableType',
@@ -94,10 +94,18 @@ export default {
         if (right && right.type !== 'match') acc.push(right);
         return acc;
       };
+      const getDiffLines = () => {
+        if (this.diffViewType === PARALLEL_DIFF_VIEW_TYPE) {
+          return (this.glFeatures.unifiedDiffLines
+            ? this.diffLines(this.diffFile)
+            : this.diffFile.parallel_diff_lines
+          ).reduce(combineSides, []);
+        }
+
+        return this.diffFile.highlighted_diff_lines;
+      };
       const side = this.line.type === 'new' ? 'right' : 'left';
-      const lines = this.diffFile.highlighted_diff_lines.length
-        ? this.diffFile.highlighted_diff_lines
-        : this.diffFile.parallel_diff_lines.reduce(combineSides, []);
+      const lines = getDiffLines();
       return commentLineOptions(lines, this.line, this.line.line_code, side);
     },
   },

changelogs/unreleased/ph-227159-fixMultiLineCommentsOptionsInParallelView.yml

+---
+title: Fixed multi line comment options in parallel mode
+merge_request:
+author:
+type: fixed

spec/features/merge_request/user_comments_on_diff_spec.rb

@@ -129,13 +129,6 @@ RSpec.describe 'User comments on a diff', :js do
         visit(diffs_project_merge_request_path(project, merge_request, view: 'parallel'))
       end
 
-      # In `files/ruby/popen.rb`
-      it 'allows comments for changes involving both sides' do
-        # click +15, select -13 add and verify comment
-        click_diff_line(find('div[data-path="files/ruby/popen.rb"] .new_line a[data-linenumber="15"]').find(:xpath, '../..'), 'right')
-        add_comment('-13', '+15')
-      end
-
       it 'allows comments to start above hidden lines and end below' do
         # click +28, select 21 add and verify comment
         click_diff_line(find('div[data-path="files/ruby/popen.rb"] .new_line a[data-linenumber="28"]').find(:xpath, '../..'), 'right')
@@ -166,7 +159,7 @@ RSpec.describe 'User comments on a diff', :js do
           all('.js-unfold-down')[1].click
         end
         click_diff_line(find('div[data-path="files/ruby/popen.rb"] .old_line a[data-linenumber="30"]').find(:xpath, '../..'), 'left')
-        add_comment('+28', '37')
+        add_comment('-9', '30')
       end
     end