Updated latestDiff logic to only be used to LegacyDiffNotes

app/assets/javascripts/diffs/store/mutations.js

@@ -86,8 +86,6 @@ export default {
   },
 
   [types.SET_LINE_DISCUSSIONS_FOR_FILE](state, { fileHash, discussions, diffPositionByLineCode }) {
-    if (!state.latestDiff) return;
-
     const selectedFile = state.diffFiles.find(f => f.fileHash === fileHash);
     const firstDiscussion = discussions[0];
     const isDiffDiscussion = firstDiscussion.diff_discussion;
@@ -99,7 +97,7 @@ export default {
       isDiffDiscussion &&
       hasLineCode &&
       diffPosition &&
-      isDiscussionApplicableToLine(firstDiscussion, diffPosition)
+      isDiscussionApplicableToLine(firstDiscussion, diffPosition, state.latestDiff)
     ) {
       const targetLine = selectedFile.parallelDiffLines.find(
         line =>

app/assets/javascripts/diffs/store/utils.js

@@ -254,7 +254,7 @@ export function getDiffPositionByLineCode(diffFiles) {
 
 // This method will check whether the discussion is still applicable
 // to the diff line in question regarding different versions of the MR
-export function isDiscussionApplicableToLine(discussion, diffPosition) {
+export function isDiscussionApplicableToLine(discussion, diffPosition, latestDiff) {
   const { lineCode, ...diffPositionCopy } = diffPosition;
 
   if (discussion.original_position && discussion.position) {
@@ -264,5 +264,5 @@ export function isDiscussionApplicableToLine(discussion, diffPosition) {
     return _.isEqual(refs, diffPositionCopy) || _.isEqual(originalRefs, diffPositionCopy);
   }
 
-  return discussion.active && lineCode === discussion.line_code;
+  return latestDiff && discussion.active && lineCode === discussion.line_code;
 }