feat(blog-plugin): limit option for blog feedOptions (#9189)

packages/docusaurus-plugin-content-blog/src/__tests__/feed.test.ts

@@ -195,4 +195,47 @@ describe.each(['atom', 'rss', 'json'])('%s', (feedType) => {
     ).toMatchSnapshot();
     fsMock.mockClear();
   });
+
+  it('filters to the first two entries using limit', async () => {
+    const siteDir = path.join(__dirname, '__fixtures__', 'website');
+    const outDir = path.join(siteDir, 'build-snap');
+    const siteConfig = {
+      title: 'Hello',
+      baseUrl: '/myBaseUrl/',
+      url: 'https://docusaurus.io',
+      favicon: 'image/favicon.ico',
+    };
+
+    // Build is quite difficult to mock, so we built the blog beforehand and
+    // copied the output to the fixture...
+    await testGenerateFeeds(
+      {
+        siteDir,
+        siteConfig,
+        i18n: DefaultI18N,
+        outDir,
+      } as LoadContext,
+      {
+        path: 'blog',
+        routeBasePath: 'blog',
+        tagsBasePath: 'tags',
+        authorsMapPath: 'authors.yml',
+        include: DEFAULT_OPTIONS.include,
+        exclude: DEFAULT_OPTIONS.exclude,
+        feedOptions: {
+          type: [feedType],
+          copyright: 'Copyright',
+          limit: 2,
+        },
+        readingTime: ({content, defaultReadingTime}) =>
+          defaultReadingTime({content}),
+        truncateMarker: /<!--\s*truncate\s*-->/,
+      } as PluginOptions,
+    );
+
+    expect(
+      fsMock.mock.calls.map((call) => call[1] as string),
+    ).toMatchSnapshot();
+    fsMock.mockClear();
+  });
 });

packages/docusaurus-plugin-content-blog/src/__tests__/options.test.ts

@@ -46,7 +46,7 @@ describe('validateOptions', () => {
     };
     expect(testValidate(userOptions)).toEqual({
       ...userOptions,
-      feedOptions: {type: ['rss'], title: 'myTitle', copyright: ''},
+      feedOptions: {type: ['rss'], title: 'myTitle', copyright: '', limit: 20},
     });
   });
 
@@ -58,7 +58,6 @@ describe('validateOptions', () => {
       beforeDefaultRehypePlugins: [markdownPluginsFunctionStub],
       remarkPlugins: [[markdownPluginsFunctionStub, {option1: '42'}]],
       rehypePlugins: [
-        // @ts-expect-error: it seems to work in practice
         markdownPluginsObjectStub,
         [markdownPluginsFunctionStub, {option1: '42'}],
       ],
@@ -95,7 +94,7 @@ describe('validateOptions', () => {
       }),
     ).toEqual({
       ...defaultOptions,
-      feedOptions: {type: ['rss', 'atom', 'json'], copyright: ''},
+      feedOptions: {type: ['rss', 'atom', 'json'], copyright: '', limit: 20},
     });
   });
 
@@ -106,7 +105,7 @@ describe('validateOptions', () => {
       }),
     ).toEqual({
       ...defaultOptions,
-      feedOptions: {type: null},
+      feedOptions: {type: null, limit: 20},
     });
   });
 
@@ -125,7 +124,12 @@ describe('validateOptions', () => {
       }),
     ).toEqual({
       ...defaultOptions,
-      feedOptions: {type: ['rss', 'atom'], title: 'title', copyright: ''},
+      feedOptions: {
+        type: ['rss', 'atom'],
+        title: 'title',
+        copyright: '',
+        limit: 20,
+      },
     });
   });
 

packages/docusaurus-plugin-content-blog/src/feed.ts

@@ -42,7 +42,12 @@ async function generateBlogFeed({
   const {url: siteUrl, baseUrl, title, favicon} = siteConfig;
   const blogBaseUrl = normalizeUrl([siteUrl, baseUrl, routeBasePath]);
 
-  const updated = blogPosts[0]?.metadata.date;
+  const blogPostsForFeed =
+    feedOptions.limit === false || feedOptions.limit === null
+      ? blogPosts
+      : blogPosts.slice(0, feedOptions.limit);
+
+  const updated = blogPostsForFeed[0]?.metadata.date;
 
   const feed = new Feed({
     id: blogBaseUrl,
@@ -59,7 +64,7 @@ async function generateBlogFeed({
     options.feedOptions.createFeedItems ?? defaultCreateFeedItems;
 
   const feedItems = await createFeedItems({
-    blogPosts,
+    blogPosts: blogPostsForFeed,
     siteConfig,
     outDir,
     defaultCreateFeedItems,

packages/docusaurus-plugin-content-blog/src/options.ts

@@ -22,7 +22,7 @@ import type {
 import type {OptionValidationContext} from '@docusaurus/types';
 
 export const DEFAULT_OPTIONS: PluginOptions = {
-  feedOptions: {type: ['rss', 'atom'], copyright: ''},
+  feedOptions: {type: ['rss', 'atom'], copyright: '', limit: 20},
   beforeDefaultRehypePlugins: [],
   beforeDefaultRemarkPlugins: [],
   admonitions: true,
@@ -123,6 +123,9 @@ const PluginOptionSchema = Joi.object<PluginOptions>({
     }),
     language: Joi.string(),
     createFeedItems: Joi.function(),
+    limit: Joi.alternatives()
+      .try(Joi.number(), Joi.valid(null), Joi.valid(false))
+      .default(DEFAULT_OPTIONS.feedOptions.limit),
   }).default(DEFAULT_OPTIONS.feedOptions),
   authorsMapPath: Joi.string().default(DEFAULT_OPTIONS.authorsMapPath),
   readingTime: Joi.function().default(() => DEFAULT_OPTIONS.readingTime),

packages/docusaurus-plugin-content-blog/src/plugin-content-blog.d.ts

@@ -272,6 +272,8 @@ yarn workspace v1.22.19image` is a collocated image path, this entry will be the
     language?: string;
     /** Allow control over the construction of BlogFeedItems */
     createFeedItems?: CreateFeedItemsFn;
+    /** Limits the feed to the specified number of posts, false|null for all */
+    limit?: number | false | null;
   };
 
   type DefaultCreateFeedItemsParams = {

website/docs/api/plugins/plugin-content-blog.mdx

@@ -68,6 +68,7 @@ Accepted fields:
 | `feedOptions` | _See below_ | `{type: ['rss', 'atom']}` | Blog feed. |
 | `feedOptions.type` | <code><a href="#FeedType">FeedType</a> \| <a href="#FeedType">FeedType</a>[] \| 'all' \| null</code> | **Required** | Type of feed to be generated. Use `null` to disable generation. |
 | `feedOptions.createFeedItems` | <code><a href="#CreateFeedItemsFn">CreateFeedItemsFn</a> \| undefined</code> | `undefined` | An optional function which can be used to transform and / or filter the items in the feed. |
+| `feedOptions.limit` | `number \| null \| false` | `20` | Limits the feed to the specified number of posts, `false` or `null` for all entries. Defaults to `20`. |
 | `feedOptions.title` | `string` | `siteConfig.title` | Title of the feed. |
 | `feedOptions.description` | `string` | <code>\`$\{siteConfig.title} Blog\`</code> | Description of the feed. |
 | `feedOptions.copyright` | `string` | `undefined` | Copyright message. |

website/docs/blog.mdx

@@ -520,6 +520,7 @@ type BlogOptions = {
     description?: string;
     copyright: string;
     language?: string; // possible values: http://www.w3.org/TR/REC-html40/struct/dirlang.html#langcodes
+    limit?: number | false | null; // defaults to 20
     /** Allow control over the construction of BlogFeedItems */
     createFeedItems?: (params: {
       blogPosts: BlogPost[];