fix(v2): linkify blog posts (#2326)

* fix(v2): linkify blog posts

* Fix tests

packages/docusaurus-plugin-content-blog/src/__tests__/__fixtures__/website/blog-with-ref/2018-12-14-Happy-First-Birthday-Slash.md

@@ -0,0 +1,5 @@
+---
+title: Happy 1st Birthday Slash!
+---
+
+pattern name

packages/docusaurus-plugin-content-blog/src/__tests__/__fixtures__/website/blog-with-ref/post.md

@@ -0,0 +1,5 @@
+---
+title: This post links to another one!
+---
+
+[Linked post](2018-12-14-Happy-First-Birthday-Slash.md)

packages/docusaurus-plugin-content-blog/src/__tests__/__snapshots__/generateBlogFeed.test.ts.snap

@@ -1,6 +1,18 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`blogFeed atom can show feed without posts 1`] = `null`;
+exports[`blogFeed atom can show feed without posts 1`] = `
+"<?xml version=\\"1.0\\" encoding=\\"utf-8\\"?>
+<feed xmlns=\\"http://www.w3.org/2005/Atom\\">
+    <id>https://docusaurus.io/blog</id>
+    <title>Hello Blog</title>
+    <updated>2015-10-25T23:29:00.000Z</updated>
+    <generator>https://github.com/jpmonette/feed</generator>
+    <link rel=\\"alternate\\" href=\\"https://docusaurus.io/blog\\"/>
+    <subtitle>Hello Blog</subtitle>
+    <icon>https://docusaurus.io/image/favicon.ico</icon>
+    <rights>Copyright</rights>
+</feed>"
+`;
 
 exports[`blogFeed atom shows feed item for each post 1`] = `
 "<?xml version=\\"1.0\\" encoding=\\"utf-8\\"?>
@@ -37,7 +49,20 @@ exports[`blogFeed atom shows feed item for each post 1`] = `
 </feed>"
 `;
 
-exports[`blogFeed rss can show feed without posts 1`] = `null`;
+exports[`blogFeed rss can show feed without posts 1`] = `
+"<?xml version=\\"1.0\\" encoding=\\"utf-8\\"?>
+<rss version=\\"2.0\\">
+    <channel>
+        <title>Hello Blog</title>
+        <link>https://docusaurus.io/blog</link>
+        <description>Hello Blog</description>
+        <lastBuildDate>Sun, 25 Oct 2015 23:29:00 GMT</lastBuildDate>
+        <docs>http://blogs.law.harvard.edu/tech/rss</docs>
+        <generator>https://github.com/jpmonette/feed</generator>
+        <copyright>Copyright</copyright>
+    </channel>
+</rss>"
+`;
 
 exports[`blogFeed rss shows feed item for each post 1`] = `
 "<?xml version=\\"1.0\\" encoding=\\"utf-8\\"?>

packages/docusaurus-plugin-content-blog/src/__tests__/__snapshots__/linkify.test.ts.snap

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`transform to correct link 1`] = `
+"---
+title: This post links to another one!
+---
+
+[Linked post](/blog/2018/12/14/Happy-First-Birthday-Slash)"
+`;

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

@@ -0,0 +1,56 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import fs from 'fs-extra';
+import path from 'path';
+import {linkify} from '../blogUtils';
+import {BlogPost} from '../types';
+
+const sitePath = path.join(__dirname, '__fixtures__', 'website');
+const blogPath = path.join(sitePath, 'blog-with-ref');
+const pluginDir = 'blog-with-ref';
+const blogPosts: BlogPost[] = [
+  {
+    id: 'Happy 1st Birthday Slash!',
+    metadata: {
+      permalink: '/blog/2018/12/14/Happy-First-Birthday-Slash',
+      source: path.join(
+        '@site',
+        pluginDir,
+        '2018-12-14-Happy-First-Birthday-Slash.md',
+      ),
+      title: 'Happy 1st Birthday Slash!',
+      description: `pattern name`,
+      date: new Date('2018-12-14'),
+      tags: [],
+      prevItem: {
+        permalink: '/blog/2019/01/01/date-matter',
+        title: 'date-matter',
+      },
+      truncated: false,
+    },
+  },
+];
+
+const transform = filepath => {
+  const content = fs.readFileSync(filepath, 'utf-8');
+  const transformedContent = linkify(content, sitePath, blogPath, blogPosts);
+  return [content, transformedContent];
+};
+
+test('transform to correct link', () => {
+  const post = path.join(blogPath, 'post.md');
+  const [content, transformedContent] = transform(post);
+  expect(transformedContent).toMatchSnapshot();
+  expect(transformedContent).toContain(
+    '](/blog/2018/12/14/Happy-First-Birthday-Slash',
+  );
+  expect(transformedContent).not.toContain(
+    '](2018-12-14-Happy-First-Birthday-Slash.md)',
+  );
+  expect(content).not.toEqual(transformedContent);
+});

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

@@ -88,7 +88,7 @@ export async function generateBlogPosts(
   const {include, routeBasePath, truncateMarker} = options;
 
   if (!fs.existsSync(blogDir)) {
-    return null;
+    return [];
   }
 
   const {baseUrl = ''} = siteConfig;
@@ -156,3 +156,48 @@ export async function generateBlogPosts(
 
   return blogPosts;
 }
+
+export function linkify(
+  fileContent: string,
+  siteDir: string,
+  blogPath: string,
+  blogPosts: BlogPost[],
+) {
+  let fencedBlock = false;
+  const lines = fileContent.split('\n').map(line => {
+    if (line.trim().startsWith('```')) {
+      fencedBlock = !fencedBlock;
+    }
+
+    if (fencedBlock) return line;
+
+    let modifiedLine = line;
+    const mdRegex = /(?:(?:\]\()|(?:\]:\s?))(?!https)([^'")\]\s>]+\.mdx?)/g;
+    let mdMatch = mdRegex.exec(modifiedLine);
+
+    while (mdMatch !== null) {
+      const mdLink = mdMatch[1];
+      const aliasedPostSource = `@site/${path.relative(
+        siteDir,
+        path.resolve(blogPath, mdLink),
+      )}`;
+      let blogPostPermalink = null;
+
+      blogPosts.forEach(blogPost => {
+        if (blogPost.metadata.source === aliasedPostSource) {
+          blogPostPermalink = blogPost.metadata.permalink;
+        }
+      });
+
+      if (blogPostPermalink) {
+        modifiedLine = modifiedLine.replace(mdLink, blogPostPermalink);
+      }
+
+      mdMatch = mdRegex.exec(modifiedLine);
+    }
+
+    return modifiedLine;
+  });
+
+  return lines.join('\n');
+}

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

@@ -18,6 +18,7 @@ import {
   TagsModule,
   BlogPaginated,
   FeedType,
+  BlogPost,
 } from './types';
 import {
   LoadContext,
@@ -75,6 +76,7 @@ export default function pluginContentBlog(
     generatedFilesDir,
     'docusaurus-plugin-content-blog',
   );
+  let blogPosts: BlogPost[] = [];
 
   return {
     name: 'docusaurus-plugin-content-blog',
@@ -89,8 +91,8 @@ export default function pluginContentBlog(
     async loadContent() {
       const {postsPerPage, routeBasePath} = options;
 
-      const blogPosts = await generateBlogPosts(contentPath, context, options);
-      if (!blogPosts) {
+      blogPosts = await generateBlogPosts(contentPath, context, options);
+      if (!blogPosts.length) {
         return null;
       }
 
@@ -391,7 +393,10 @@ export default function pluginContentBlog(
                 {
                   loader: path.resolve(__dirname, './markdownLoader.js'),
                   options: {
+                    siteDir,
+                    contentPath,
                     truncateMarker,
+                    blogPosts,
                   },
                 },
               ].filter(Boolean) as Loader[],

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

@@ -5,21 +5,20 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-const {parseQuery, getOptions} = require('loader-utils');
 import {loader} from 'webpack';
-import {truncate} from './blogUtils';
+import {truncate, linkify} from './blogUtils';
+const {parseQuery, getOptions} = require('loader-utils');
 
 export = function(fileString: string) {
   const callback = this.async();
-
-  const {truncateMarker}: {truncateMarker: RegExp} = getOptions(this);
-
-  let finalContent = fileString;
+  const {truncateMarker, siteDir, contentPath, blogPosts} = getOptions(this);
+  // Linkify posts
+  let finalContent = linkify(fileString, siteDir, contentPath, blogPosts);
 
   // Truncate content if requested (e.g: file.md?truncated=true).
   const {truncated} = this.resourceQuery && parseQuery(this.resourceQuery);
   if (truncated) {
-    finalContent = truncate(fileString, truncateMarker);
+    finalContent = truncate(finalContent, truncateMarker);
   }
 
   return callback && callback(null, finalContent);