1 files changed, 50 insertions, 3 deletions

diff --git a/app/assets/javascripts/diffs/store/utils.js b/app/assets/javascripts/diffs/store/utils.js
index dd8dec49a37..2be71c77087 100644
--- a/app/assets/javascripts/diffs/store/utils.js
+++ b/app/assets/javascripts/diffs/store/utils.js
@@ -233,7 +233,7 @@ export function trimFirstCharOfLineContent(line = {}) {
   // eslint-disable-next-line no-param-reassign
   delete line.text;
 
-  const parsedLine = Object.assign({}, line);
+  const parsedLine = { ...line };
 
   if (line.rich_text) {
     const firstChar = parsedLine.rich_text.charAt(0);
@@ -303,6 +303,42 @@ function prepareLine(line) {
   }
 }
 
+export function prepareLineForRenamedFile({ line, diffViewType, diffFile, index = 0 }) {
+  /*
+    Renamed files are a little different than other diffs, which
+    is why this is distinct from `prepareDiffFileLines` below.
+
+    We don't get any of the diff file context when we get the diff
+    (so no "inline" vs. "parallel", no "line_code", etc.).
+
+    We can also assume that both the left and the right of each line
+    (for parallel diff view type) are identical, because the file
+    is renamed, not modified.
+
+    This should be cleaned up as part of the effort around flattening our data
+    ==> https://gitlab.com/groups/gitlab-org/-/epics/2852#note_304803402
+  */
+  const lineNumber = index + 1;
+  const cleanLine = {
+    ...line,
+    line_code: `${diffFile.file_hash}_${lineNumber}_${lineNumber}`,
+    new_line: lineNumber,
+    old_line: lineNumber,
+  };
+
+  prepareLine(cleanLine); // WARNING: In-Place Mutations!
+
+  if (diffViewType === PARALLEL_DIFF_VIEW_TYPE) {
+    return {
+      left: { ...cleanLine },
+      right: { ...cleanLine },
+      line_code: cleanLine.line_code,
+    };
+  }
+
+  return cleanLine;
+}
+
 function prepareDiffFileLines(file) {
   const inlineLines = file.highlighted_diff_lines;
   const parallelLines = file.parallel_diff_lines;
@@ -437,7 +473,11 @@ export function getDiffPositionByLineCode(diffFiles, useSingleDiffStyle) {
 // 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, latestDiff }) {
-  const { line_code, ...diffPositionCopy } = diffPosition;
+  const { line_code, ...dp } = diffPosition;
+  // Removing `line_range` from diffPosition because the backend does not
+  // yet consistently return this property. This check can be removed,
+  // once this is addressed. see https://gitlab.com/gitlab-org/gitlab/-/issues/213010
+  const { line_range: dpNotUsed, ...diffPositionCopy } = dp;
 
   if (discussion.original_position && discussion.position) {
     const discussionPositions = [
@@ -446,7 +486,14 @@ export function isDiscussionApplicableToLine({ discussion, diffPosition, latestD
       ...(discussion.positions || []),
     ];
 
-    return discussionPositions.some(position => isEqual(position, diffPositionCopy));
+    const removeLineRange = position => {
+      const { line_range: pNotUsed, ...positionNoLineRange } = position;
+      return positionNoLineRange;
+    };
+
+    return discussionPositions
+      .map(removeLineRange)
+      .some(position => isEqual(position, diffPositionCopy));
   }
 
   // eslint-disable-next-line