Separate metadata processing from normal diff processing

There are basically two changes here:

- Make the argument to prepareDiffData an object so that
    the arguments list isn't unwieldy (majority of changes)
- Skip identifying diff files when the preparation is for metadata,
    since those diff "files" don't have uniquely identifying data

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

@@ -191,7 +191,13 @@ export const fetchDiffFilesMeta = ({ commit, state }) => {
       commit(types.SET_MERGE_REQUEST_DIFFS, data.merge_request_diffs || []);
       commit(types.SET_DIFF_METADATA, strippedData);
 
-      worker.postMessage(prepareDiffData(data, state.diffFiles));
+      worker.postMessage(
+        prepareDiffData({
+          diff: data,
+          priorFiles: state.diffFiles,
+          meta: true,
+        }),
+      );
 
       return data;
     })

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

@@ -73,7 +73,10 @@ export default {
   },
 
   [types.SET_DIFF_DATA_BATCH](state, data) {
-    const files = prepareDiffData(data, state.diffFiles);
+    const files = prepareDiffData({
+      diff: data,
+      priorFiles: state.diffFiles,
+    });
 
     Object.assign(state, {
       ...convertObjectPropsToCamelCase(data),
@@ -143,7 +146,7 @@ export default {
   },
 
   [types.ADD_COLLAPSED_DIFFS](state, { file, data }) {
-    const files = prepareDiffData(data);
+    const files = prepareDiffData({ diff: data });
     const [newFileData] = files.filter(f => f.file_hash === file.file_hash);
     const selectedFile = state.diffFiles.find(f => f.file_hash === file.file_hash);
     Object.assign(selectedFile, { ...newFileData });

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

@@ -386,9 +386,9 @@ function deduplicateFilesList(files) {
   return Object.values(dedupedFiles);
 }
 
-export function prepareDiffData(diff, priorFiles = []) {
+export function prepareDiffData({ diff, priorFiles = [], meta = false }) {
   const cleanedFiles = (diff.diff_files || [])
-    .map((file, index, allFiles) => prepareRawDiffFile({ file, allFiles }))
+    .map((file, index, allFiles) => prepareRawDiffFile({ file, allFiles, meta }))
     .map(ensureBasicDiffFileLines)
     .map(prepareDiffFileLines)
     .map(finalizeDiffFile);

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

@@ -33,23 +33,26 @@ function collapsed(file) {
   };
 }
 
-export function identifier({ file }) {
+function identifier(file) {
   return uuids({
     seeds: [file.file_identifier_hash, file.content_sha],
   })[0];
 }
 
-export function prepareRawDiffFile({ file, allFiles }) {
-  Object.assign(file, {
-    id: identifier({ file }),
+export function prepareRawDiffFile({ file, allFiles, meta = false }) {
+  const additionalProperties = {
     brokenSymlink: fileSymlinkInformation(file, allFiles),
     viewer: {
       ...file.viewer,
       ...collapsed(file),
     },
-  });
+  };
+
+  if (!meta) {
+    additionalProperties.id = identifier(file);
+  }
 
-  return file;
+  return Object.assign(file, additionalProperties);
 }
 
 export function collapsedType(file) {

spec/frontend/diffs/store/utils_spec.js

@@ -409,10 +409,13 @@ describe('DiffsStoreUtils', () => {
           diff_files: [{ ...mock, [INLINE_DIFF_LINES_KEY]: undefined }],
         };
 
-        preparedDiff.diff_files = utils.prepareDiffData(preparedDiff);
-        splitInlineDiff.diff_files = utils.prepareDiffData(splitInlineDiff);
-        splitParallelDiff.diff_files = utils.prepareDiffData(splitParallelDiff);
-        completedDiff.diff_files = utils.prepareDiffData(completedDiff, [mock]);
+        preparedDiff.diff_files = utils.prepareDiffData({ diff: preparedDiff });
+        splitInlineDiff.diff_files = utils.prepareDiffData({ diff: splitInlineDiff });
+        splitParallelDiff.diff_files = utils.prepareDiffData({ diff: splitParallelDiff });
+        completedDiff.diff_files = utils.prepareDiffData({
+          diff: completedDiff,
+          priorFiles: [mock],
+        });
       });
 
       it('sets the renderIt and collapsed attribute on files', () => {
@@ -447,7 +450,10 @@ describe('DiffsStoreUtils', () => {
           content_sha: 'ABC',
           file_hash: 'DEF',
         };
-        const updatedFilesList = utils.prepareDiffData({ diff_files: [fakeNewFile] }, priorFiles);
+        const updatedFilesList = utils.prepareDiffData({
+          diff: { diff_files: [fakeNewFile] },
+          priorFiles,
+        });
 
         expect(updatedFilesList).toEqual([mock, fakeNewFile]);
       });
@@ -460,7 +466,10 @@ describe('DiffsStoreUtils', () => {
           { ...mock, [INLINE_DIFF_LINES_KEY]: undefined },
           { ...mock, [INLINE_DIFF_LINES_KEY]: undefined, content_sha: 'ABC', file_hash: 'DEF' },
         ];
-        const updatedFilesList = utils.prepareDiffData({ diff_files: fakeBatch }, priorFiles);
+        const updatedFilesList = utils.prepareDiffData({
+          diff: { diff_files: fakeBatch },
+          priorFiles,
+        });
 
         expect(updatedFilesList).toEqual([
           mock,
@@ -498,7 +507,7 @@ describe('DiffsStoreUtils', () => {
       beforeEach(() => {
         mock = getDiffMetadataMock();
 
-        preparedDiffFiles = utils.prepareDiffData(mock);
+        preparedDiffFiles = utils.prepareDiffData({ diff: mock, meta: true });
       });
 
       it('sets the renderIt and collapsed attribute on files', () => {
@@ -514,7 +523,7 @@ describe('DiffsStoreUtils', () => {
         const fileMock = getDiffFileMock();
         const metaData = getDiffMetadataMock();
         const priorFiles = [fileMock];
-        const updatedFilesList = utils.prepareDiffData(metaData, priorFiles);
+        const updatedFilesList = utils.prepareDiffData({ diff: metaData, priorFiles, meta: true });
 
         expect(updatedFilesList.length).toEqual(2);
         expect(updatedFilesList[0]).toEqual(fileMock);
@@ -539,7 +548,7 @@ describe('DiffsStoreUtils', () => {
         const fileMock = getDiffFileMock();
         const metaMock = getDiffMetadataMock();
         const priorFiles = [{ ...fileMock }];
-        const updatedFilesList = utils.prepareDiffData(metaMock, priorFiles);
+        const updatedFilesList = utils.prepareDiffData({ diff: metaMock, priorFiles, meta: true });
 
         expect(updatedFilesList).toEqual([
           fileMock,

spec/frontend/diffs/utils/diff_file_spec.js

@@ -2,24 +2,44 @@ import { prepareRawDiffFile } from '~/diffs/utils/diff_file';
 
 const DIFF_FILES = [
   {
+    blob: {
+      id: 'abc',
+      mode: '100644',
+    },
     file_hash: 'ABC', // This file is just a normal file
   },
   {
+    blob: {
+      id: 'bcd',
+      mode: '100644',
+    },
     file_hash: 'DEF', // This file replaces a symlink
     a_mode: '0',
     b_mode: '0755',
   },
   {
+    blob: {
+      id: 'cde',
+      mode: '100644',
+    },
     file_hash: 'DEF', // This symlink is replaced by a file
     a_mode: '120000',
     b_mode: '0',
   },
   {
+    blob: {
+      id: 'def',
+      mode: '100644',
+    },
     file_hash: 'GHI', // This symlink replaces a file
     a_mode: '0',
     b_mode: '120000',
   },
   {
+    blob: {
+      id: 'efg',
+      mode: '100644',
+    },
     file_hash: 'GHI', // This file is replaced by a symlink
     a_mode: '0755',
     b_mode: '0',