fix(v2): sidebar autogen from subfolder should read category metadata correctly

packages/docusaurus-plugin-content-docs/src/__tests__/__fixtures__/site-with-autogenerated-sidebar/partialAutogeneratedSidebars2.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+module.exports = {
+  someSidebar: [
+    {type: 'doc', id: 'API/api-end'},
+    {
+      type: 'autogenerated',
+      dirName: '3-API',
+    },
+  ],
+};

packages/docusaurus-plugin-content-docs/src/__tests__/index.test.ts

@@ -1493,6 +1493,88 @@ describe('site with partial autogenerated sidebars', () => {
   });
 });
 
+describe('site with partial autogenerated sidebars 2 (fix #4638)', () => {
+  // Test added for edge case https://github.com/facebook/docusaurus/issues/4638
+
+  async function loadSite() {
+    const siteDir = path.join(
+      __dirname,
+      '__fixtures__',
+      'site-with-autogenerated-sidebar',
+    );
+    const context = await loadContext(siteDir, {});
+    const plugin = pluginContentDocs(
+      context,
+      normalizePluginOptions(OptionsSchema, {
+        path: 'docs',
+        sidebarPath: path.join(
+          __dirname,
+          '__fixtures__',
+          'site-with-autogenerated-sidebar',
+          'partialAutogeneratedSidebars2.js',
+        ),
+      }),
+    );
+
+    const content = (await plugin.loadContent?.())!;
+
+    return {content, siteDir};
+  }
+
+  test('sidebar is partially autogenerated', async () => {
+    const {content} = await loadSite();
+    const version = content.loadedVersions[0];
+
+    expect(version.sidebars).toEqual({
+      someSidebar: [
+        {
+          type: 'doc',
+          id: 'API/api-end',
+        },
+        {
+          type: 'doc',
+          id: 'API/api-overview',
+        },
+        {
+          type: 'category',
+          label: 'Core APIs',
+          collapsed: true,
+          items: [
+            {
+              type: 'doc',
+
+              id: 'API/Core APIs/Client API',
+            },
+            {
+              type: 'doc',
+              id: 'API/Core APIs/Server API',
+            },
+          ],
+        },
+        {
+          type: 'category',
+          label: 'Extension APIs (label from _category_.yml)', // Fix #4638
+          collapsed: true,
+          items: [
+            {
+              type: 'doc',
+              id: 'API/Extension APIs/Plugin API',
+            },
+            {
+              type: 'doc',
+              id: 'API/Extension APIs/Theme API',
+            },
+          ],
+        },
+        {
+          type: 'doc',
+          id: 'API/api-end',
+        },
+      ],
+    });
+  });
+});
+
 describe('site with custom sidebar items generator', () => {
   async function loadSite(sidebarItemsGenerator: SidebarItemsGenerator) {
     const siteDir = path.join(

packages/docusaurus-plugin-content-docs/src/__tests__/sidebarItemsGenerator.test.ts

@@ -219,6 +219,20 @@ describe('DefaultSidebarItemsGenerator', () => {
   });
 
   test('generates subfolder sidebar', async () => {
+    // Ensure that category metadata file is correctly read
+    // fix edge case found in https://github.com/facebook/docusaurus/issues/4638
+    mockCategoryMetadataFiles({
+      'subfolder/subsubfolder/subsubsubfolder2/_category_.yml': {
+        position: 2,
+        label: 'subsubsubfolder2 (_category_.yml label)',
+      },
+      'subfolder/subsubfolder/subsubsubfolder3/_category_.json': {
+        position: 1,
+        label: 'subsubsubfolder3 (_category_.json label)',
+        collapsed: false,
+      },
+    });
+
     const sidebarSlice = await DefaultSidebarItemsGenerator({
       item: {
         type: 'autogenerated',
@@ -257,12 +271,61 @@ describe('DefaultSidebarItemsGenerator', () => {
           sidebarPosition: undefined,
           frontMatter: {},
         },
+        {
+          id: 'doc5',
+          source: 'doc5.md',
+          sourceDirName: 'subfolder/subsubfolder/subsubsubfolder',
+          sidebarPosition: undefined,
+          frontMatter: {},
+        },
+        {
+          id: 'doc6',
+          source: 'doc6.md',
+          sourceDirName: 'subfolder/subsubfolder/subsubsubfolder2',
+          sidebarPosition: undefined,
+          frontMatter: {},
+        },
+        {
+          id: 'doc7',
+          source: 'doc7.md',
+          sourceDirName: 'subfolder/subsubfolder/subsubsubfolder3',
+          sidebarPosition: 2,
+          frontMatter: {},
+        },
+        {
+          id: 'doc8',
+          source: 'doc8.md',
+          sourceDirName: 'subfolder/subsubfolder/subsubsubfolder3',
+          sidebarPosition: 1,
+          frontMatter: {},
+        },
       ],
     });
 
     expect(sidebarSlice).toEqual([
+      {
+        type: 'category',
+        label: 'subsubsubfolder3 (_category_.json label)',
+        collapsed: false,
+        items: [
+          {type: 'doc', id: 'doc8'},
+          {type: 'doc', id: 'doc7'},
+        ],
+      },
+      {
+        type: 'category',
+        label: 'subsubsubfolder2 (_category_.yml label)',
+        collapsed: true,
+        items: [{type: 'doc', id: 'doc6'}],
+      },
       {type: 'doc', id: 'doc1'},
       {type: 'doc', id: 'doc4'},
+      {
+        type: 'category',
+        label: 'subsubsubfolder',
+        collapsed: true,
+        items: [{type: 'doc', id: 'doc5'}],
+      },
     ] as Sidebar);
   });
 });

packages/docusaurus-plugin-content-docs/src/sidebarItemsGenerator.ts

@@ -186,6 +186,7 @@ export const DefaultSidebarItemsGenerator: SidebarItemsGenerator = async functio
   }): Promise<SidebarItemCategory & WithPosition> {
     const categoryDirPath = path.join(
       version.contentPath,
+      item.dirName, // fix https://github.com/facebook/docusaurus/issues/4638
       breadcrumb.join(BreadcrumbSeparator),
     );