1 files changed, 41 insertions, 39 deletions

diff --git a/app/assets/javascripts/diffs/store/mutations.js b/app/assets/javascripts/diffs/store/mutations.js
index a4986e26966..8cfdded1f9b 100644
--- a/app/assets/javascripts/diffs/store/mutations.js
+++ b/app/assets/javascripts/diffs/store/mutations.js
@@ -45,26 +45,28 @@ export default {
   },
 
   [types.SET_DIFF_DATA](state, data) {
+    let files = state.diffFiles;
+
     if (
-      !(
-        gon &&
-        gon.features &&
-        gon.features.diffsBatchLoad &&
-        window.location.search.indexOf('diff_id') === -1
-      )
+      !(gon?.features?.diffsBatchLoad && window.location.search.indexOf('diff_id') === -1) &&
+      data.diff_files
     ) {
-      prepareDiffData(data);
+      files = prepareDiffData(data, files);
     }
 
     Object.assign(state, {
       ...convertObjectPropsToCamelCase(data),
+      diffFiles: files,
     });
   },
 
   [types.SET_DIFF_DATA_BATCH](state, data) {
-    prepareDiffData(data);
+    const files = prepareDiffData(data, state.diffFiles);
 
-    state.diffFiles.push(...data.diff_files);
+    Object.assign(state, {
+      ...convertObjectPropsToCamelCase(data),
+      diffFiles: files,
+    });
   },
 
   [types.RENDER_FILE](state, file) {
@@ -88,11 +90,11 @@ export default {
 
     if (!diffFile) return;
 
-    if (diffFile.highlighted_diff_lines) {
+    if (diffFile.highlighted_diff_lines.length) {
       diffFile.highlighted_diff_lines.find(l => l.line_code === lineCode).hasForm = hasForm;
     }
 
-    if (diffFile.parallel_diff_lines) {
+    if (diffFile.parallel_diff_lines.length) {
       const line = diffFile.parallel_diff_lines.find(l => {
         const { left, right } = l;
 
@@ -153,13 +155,13 @@ export default {
   },
 
   [types.EXPAND_ALL_FILES](state) {
-    state.diffFiles = state.diffFiles.map(file => ({
-      ...file,
-      viewer: {
-        ...file.viewer,
-        collapsed: false,
-      },
-    }));
+    state.diffFiles.forEach(file => {
+      Object.assign(file, {
+        viewer: Object.assign(file.viewer, {
+          collapsed: false,
+        }),
+      });
+    });
   },
 
   [types.SET_LINE_DISCUSSIONS_FOR_FILE](state, { discussion, diffPositionByLineCode, hash }) {
@@ -197,29 +199,29 @@ export default {
       };
     };
 
-    state.diffFiles = state.diffFiles.map(diffFile => {
-      if (diffFile.file_hash === fileHash) {
-        const file = { ...diffFile };
-
-        if (file.highlighted_diff_lines) {
-          file.highlighted_diff_lines = file.highlighted_diff_lines.map(line =>
-            setDiscussionsExpanded(lineCheck(line) ? mapDiscussions(line) : line),
-          );
+    state.diffFiles.forEach(file => {
+      if (file.file_hash === fileHash) {
+        if (file.highlighted_diff_lines.length) {
+          file.highlighted_diff_lines.forEach(line => {
+            Object.assign(
+              line,
+              setDiscussionsExpanded(lineCheck(line) ? mapDiscussions(line) : line),
+            );
+          });
         }
 
-        if (file.parallel_diff_lines) {
-          file.parallel_diff_lines = file.parallel_diff_lines.map(line => {
+        if (file.parallel_diff_lines.length) {
+          file.parallel_diff_lines.forEach(line => {
             const left = line.left && lineCheck(line.left);
             const right = line.right && lineCheck(line.right);
 
             if (left || right) {
-              return {
-                ...line,
+              Object.assign(line, {
                 left: line.left ? setDiscussionsExpanded(mapDiscussions(line.left)) : null,
                 right: line.right
                   ? setDiscussionsExpanded(mapDiscussions(line.right, () => !left))
                   : null,
-              };
+              });
             }
 
             return line;
@@ -227,15 +229,15 @@ export default {
         }
 
         if (!file.parallel_diff_lines || !file.highlighted_diff_lines) {
-          file.discussions = (file.discussions || [])
+          const newDiscussions = (file.discussions || [])
             .filter(d => d.id !== discussion.id)
             .concat(discussion);
-        }
 
-        return file;
+          Object.assign(file, {
+            discussions: newDiscussions,
+          });
+        }
       }
-
-      return diffFile;
     });
   },
 
@@ -259,9 +261,9 @@ export default {
   [types.TOGGLE_LINE_DISCUSSIONS](state, { fileHash, lineCode, expanded }) {
     const selectedFile = state.diffFiles.find(f => f.file_hash === fileHash);
 
-    updateLineInFile(selectedFile, lineCode, line =>
-      Object.assign(line, { discussionsExpanded: expanded }),
-    );
+    updateLineInFile(selectedFile, lineCode, line => {
+      Object.assign(line, { discussionsExpanded: expanded });
+    });
   },
 
   [types.TOGGLE_FOLDER_OPEN](state, path) {