feat(v2): provide doc sidebar_label through sidebars.js (#4500)

* feat : update SidebarItemDoc type

* feat : update assertIsDoc

* feat : allow configuring title from sidebar.js

* feat : add docs

* docs : refactor i18n docs to use label in sidebar.js

* test : add test

* Update website/docs/guides/docs/sidebar.md

Co-authored-by: Sébastien Lorber <slorber@users.noreply.github.com>

* docs : remove backported docs

Co-authored-by: Lisa Chandra <52909743+lisa761@users.noreply.github.com>
Co-authored-by: Javid <singularity.javid@gmail.com>
Co-authored-by: Sébastien Lorber <slorber@users.noreply.github.com>

packages/docusaurus-plugin-content-docs/src/__tests__/__fixtures__/site-with-doc-label/docs/hello-1.md

@@ -0,0 +1,7 @@
+---
+id: hello-1
+title: Hello 1
+---
+
+Hello World 1!
+

packages/docusaurus-plugin-content-docs/src/__tests__/__fixtures__/site-with-doc-label/docs/hello-2.md

@@ -0,0 +1,8 @@
+---
+id: hello-2
+title: Hello 2
+sidebar_label: Hello 2 From Doc
+---
+
+Hello World 2!
+

packages/docusaurus-plugin-content-docs/src/__tests__/__fixtures__/site-with-doc-label/docusaurus.config.js

@@ -0,0 +1,14 @@
+/**
+ * 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 = {
+  title: 'My Site',
+  tagline: 'The tagline of my site',
+  url: 'https://your-docusaurus-test-site.com',
+  baseUrl: '/',
+  favicon: 'img/favicon.ico',
+};

packages/docusaurus-plugin-content-docs/src/__tests__/__fixtures__/site-with-doc-label/sidebars.json

@@ -0,0 +1,14 @@
+{
+  "docs": [
+    {
+      "id": "hello-1",
+      "type": "doc",
+      "label": "Hello One"
+    },
+    {
+      "id": "hello-2",
+      "type": "doc",
+      "label": "Hello Two"
+    }
+  ]
+}

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

@@ -677,3 +677,39 @@ describe('versioned website (community)', () => {
     utils.expectSnapshot();
   });
 });
+
+describe('site with doc label', () => {
+  async function loadSite() {
+    const siteDir = path.join(__dirname, '__fixtures__', 'site-with-doc-label');
+    const context = await loadContext(siteDir);
+    const sidebarPath = path.join(siteDir, 'sidebars.json');
+    const plugin = pluginContentDocs(
+      context,
+      normalizePluginOptions(OptionsSchema, {
+        path: 'docs',
+        sidebarPath,
+        homePageId: 'hello-1',
+      }),
+    );
+
+    const content = await plugin.loadContent();
+
+    return {content};
+  }
+
+  test('label in sidebar.json is used', async () => {
+    const {content} = await loadSite();
+    const loadedVersion = content.loadedVersions[0];
+    const sidebarProps = toSidebarsProp(loadedVersion);
+
+    expect(sidebarProps.docs[0].label).toBe('Hello One');
+  });
+
+  test('sidebar_label in doc has higher precedence over label in sidebar.json', async () => {
+    const {content} = await loadSite();
+    const loadedVersion = content.loadedVersions[0];
+    const sidebarProps = toSidebarsProp(loadedVersion);
+
+    expect(sidebarProps.docs[1].label).toBe('Hello 2 From Doc');
+  });
+});