Dont allow diff commenting if MR locked

app/assets/javascripts/diff.js

@@ -17,7 +17,8 @@ class Diff {
       }
     });
 
-    FilesCommentButton.init($diffFile);
+    const tab = document.getElementById('diffs');
+    if (tab && tab.dataset.isLocked === 'false') FilesCommentButton.init($diffFile);
 
     $diffFile.each((index, file) => new gl.ImageFile(file));
 

app/views/projects/merge_requests/show.html.haml

@@ -80,7 +80,7 @@
       #pipelines.pipelines.tab-pane
         - if @pipelines.any?
           = render 'projects/commit/pipelines_list', disable_initialization: true, endpoint: pipelines_project_merge_request_path(@project, @merge_request)
-      #diffs.diffs.tab-pane
+      #diffs.diffs.tab-pane{ data: { "is-locked" => @merge_request.discussion_locked?.to_s } }
         -# This tab is always loaded via AJAX
 
     .mr-loading-status