perf: avoid duplicated git log calls in loadContent() and postBuild() for untracked Git files (#11211)

Co-authored-by: slorber <749374+slorber@users.noreply.github.com>

packages/docusaurus-utils/src/__tests__/lastUpdateUtils.test.ts

@@ -14,8 +14,10 @@ import execa from 'execa';
 import {
   getGitLastUpdate,
   LAST_UPDATE_FALLBACK,
+  LAST_UPDATE_UNTRACKED_GIT_FILEPATH,
   readLastUpdateData,
 } from '../lastUpdateUtils';
+import type {FrontMatterLastUpdate} from '../lastUpdateUtils';
 
 describe('getGitLastUpdate', () => {
   const {repoDir} = createTempRepo();
@@ -109,6 +111,34 @@ describe('readLastUpdateData', () => {
   const testTimestamp = new Date(testDate).getTime();
   const testAuthor = 'ozaki';
 
+  describe('on untracked Git file', () => {
+    function test(lastUpdateFrontMatter: FrontMatterLastUpdate | undefined) {
+      return readLastUpdateData(
+        LAST_UPDATE_UNTRACKED_GIT_FILEPATH,
+        {showLastUpdateAuthor: true, showLastUpdateTime: true},
+        lastUpdateFrontMatter,
+      );
+    }
+
+    it('reads null at/by from Git', async () => {
+      const {lastUpdatedAt, lastUpdatedBy} = await test({});
+      expect(lastUpdatedAt).toBeNull();
+      expect(lastUpdatedBy).toBeNull();
+    });
+
+    it('reads null at from Git and author from front matter', async () => {
+      const {lastUpdatedAt, lastUpdatedBy} = await test({author: testAuthor});
+      expect(lastUpdatedAt).toBeNull();
+      expect(lastUpdatedBy).toEqual(testAuthor);
+    });
+
+    it('reads null by from Git and date from front matter', async () => {
+      const {lastUpdatedAt, lastUpdatedBy} = await test({date: testDate});
+      expect(lastUpdatedBy).toBeNull();
+      expect(lastUpdatedAt).toEqual(testTimestamp);
+    });
+  });
+
   it('read last time show author time', async () => {
     const {lastUpdatedAt, lastUpdatedBy} = await readLastUpdateData(
       '',

packages/docusaurus-utils/src/gitUtils.ts

@@ -154,12 +154,12 @@ export async function getFileCommitDate(
     file,
   )}"`;
 
-  const result = (await GitCommandQueue.add(() =>
-    execa(command, {
+  const result = (await GitCommandQueue.add(() => {
+    return execa(command, {
       cwd: path.dirname(file),
       shell: true,
-    }),
-  ))!;
+    });
+  }))!;
 
   if (result.exitCode !== 0) {
     throw new Error(

packages/docusaurus-utils/src/lastUpdateUtils.ts

@@ -15,10 +15,18 @@ import {
 import type {PluginOptions} from '@docusaurus/types';
 
 export type LastUpdateData = {
-  /** A timestamp in **milliseconds**, usually read from `git log` */
-  lastUpdatedAt?: number;
-  /** The author's name, usually coming from `git log` */
-  lastUpdatedBy?: string;
+  /**
+   * A timestamp in **milliseconds**, usually read from `git log`
+   * `undefined`: not read
+   * `null`: no value to read (usual for untracked files)
+   */
+  lastUpdatedAt: number | undefined | null;
+  /**
+   * The author's name, usually coming from `git log`
+   * `undefined`: not read
+   * `null`: no value to read (usual for untracked files)
+   */
+  lastUpdatedBy: string | undefined | null;
 };
 
 let showedGitRequirementError = false;
@@ -68,9 +76,15 @@ export const LAST_UPDATE_FALLBACK: LastUpdateData = {
   lastUpdatedBy: 'Author',
 };
 
+// Not proud of this, but convenient for tests :/
+export const LAST_UPDATE_UNTRACKED_GIT_FILEPATH = `file/path/${Math.random()}.mdx`;
+
 export async function getLastUpdate(
   filePath: string,
 ): Promise<LastUpdateData | null> {
+  if (filePath === LAST_UPDATE_UNTRACKED_GIT_FILEPATH) {
+    return null;
+  }
   if (
     process.env.NODE_ENV !== 'production' ||
     process.env.DOCUSAURUS_DISABLE_LAST_UPDATE === 'true'
@@ -103,7 +117,7 @@ export async function readLastUpdateData(
   const {showLastUpdateAuthor, showLastUpdateTime} = options;
 
   if (!showLastUpdateAuthor && !showLastUpdateTime) {
-    return {};
+    return {lastUpdatedBy: undefined, lastUpdatedAt: undefined};
   }
 
   const frontMatterAuthor = lastUpdateFrontMatter?.author;
@@ -116,9 +130,21 @@ export async function readLastUpdateData(
   // If all the data is provided as front matter, we do not call it
   const getLastUpdateMemoized = _.memoize(() => getLastUpdate(filePath));
   const getLastUpdateBy = () =>
-    getLastUpdateMemoized().then((update) => update?.lastUpdatedBy);
+    getLastUpdateMemoized().then((update) => {
+      // Important, see https://github.com/facebook/docusaurus/pull/11211
+      if (update === null) {
+        return null;
+      }
+      return update?.lastUpdatedBy;
+    });
   const getLastUpdateAt = () =>
-    getLastUpdateMemoized().then((update) => update?.lastUpdatedAt);
+    getLastUpdateMemoized().then((update) => {
+      // Important, see https://github.com/facebook/docusaurus/pull/11211
+      if (update === null) {
+        return null;
+      }
+      return update?.lastUpdatedAt;
+    });
 
   const lastUpdatedBy = showLastUpdateAuthor
     ? frontMatterAuthor ?? (await getLastUpdateBy())