feat(blog): add options.createFeedItems to filter/limit/transform feed items

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

@@ -143,4 +143,47 @@ describe.each(['atom', 'rss', 'json'])('%s', (feedType) => {
     ).toMatchSnapshot();
     fsMock.mockClear();
   });
+
+  it('filters to the first two entries', 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',
+          filter: (items, index) => index < 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/feed.ts

@@ -154,9 +154,12 @@ export async function createBlogFeedFiles({
   locale: string;
 }): Promise<void> {
   const blogPosts = allBlogPosts.filter(shouldBeInFeed);
+  const filteredBlogPosts = options.feedOptions.filter
+    ? blogPosts.filter(options.feedOptions.filter)
+    : blogPosts;
 
   const feed = await generateBlogFeed({
-    blogPosts,
+    blogPosts: filteredBlogPosts,
     options,
     siteConfig,
     outDir,

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

@@ -124,6 +124,7 @@ const PluginOptionSchema = Joi.object<PluginOptions>({
         .default(DEFAULT_OPTIONS.feedOptions.copyright),
     }),
     language: Joi.string(),
+    filter: Joi.function(),
   }).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

@@ -263,6 +263,8 @@ declare module '@docusaurus/plugin-content-blog' {
     copyright: string;
     /** Language of the feed. */
     language?: string;
+    /** Filter that can be applied to reduce the number of entries */
+    filter?: (blogPost: BlogPost, index: number) => boolean;
   };
 
   /**

website/docs/blog.mdx

@@ -511,6 +511,7 @@ type BlogOptions = {
     description?: string;
     copyright: string;
     language?: string; // possible values: http://www.w3.org/TR/REC-html40/struct/dirlang.html#langcodes
+    filter?: (blogPost: BlogPost, index?: number) => boolean;
   };
 };
 ```

website/docusaurus.config.js

@@ -341,6 +341,7 @@ const config = {
           feedOptions: {
             type: 'all',
             copyright: `Copyright © ${new Date().getFullYear()} Facebook, Inc.`,
+            filter: (items, index) => index < 2,
           },
           blogSidebarCount: 'ALL',
           blogSidebarTitle: 'All our posts',