misc(v2): change blog front matter to snake_case (#1989)

* misc(v2): change blog front matter to snake_case

* Fix blog image url

* Add docs for change

* More migration docs

packages/docusaurus-init/templates/classic/blog/2019-05-28-hola.md

@@ -2,10 +2,9 @@
 id: hola
 title: Hola
 author: Gao Wei
-authorTitle: Docusaurus Core Team
-authorURL: https://github.com/wgao19
-authorImageURL: https://avatars1.githubusercontent.com/u/2055384?v=4
-authorTwitter: wgao19
+author_title: Docusaurus Core Team
+author_url: https://github.com/wgao19
+author_image_url: https://avatars1.githubusercontent.com/u/2055384?v=4
 tags: [hola, docusaurus]
 ---
 

packages/docusaurus-init/templates/classic/blog/2019-05-29-hello-world.md

@@ -2,10 +2,9 @@
 id: hello-world
 title: Hello
 author: Endilie Yacop Sucipto
-authorTitle: Maintainer of Docusaurus
-authorURL: https://github.com/endiliey
-authorImageURL: https://avatars1.githubusercontent.com/u/17883920?s=460&v=4
-authorTwitter: endiliey
+author_title: Maintainer of Docusaurus
+author_url: https://github.com/endiliey
+author_image_url: https://avatars1.githubusercontent.com/u/17883920?s=460&v=4
 tags: [hello, docusaurus]
 ---
 

packages/docusaurus-init/templates/classic/blog/2019-05-30-welcome.md

@@ -2,10 +2,9 @@
 id: welcome
 title: Welcome
 author: Yangshun Tay
-authorTitle: Front End Engineer @ Facebook
-authorURL: https://github.com/yangshun
-authorImageURL: https://avatars0.githubusercontent.com/u/1315101?s=400&v=4
-authorTwitter: yangshunz
+author_title: Front End Engineer @ Facebook
+author_url: https://github.com/yangshun
+author_image_url: https://avatars0.githubusercontent.com/u/1315101?s=400&v=4
 tags: [facebook, hello, docusaurus]
 ---
 

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

@@ -1,3 +1,10 @@
+/**
+ * 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 globby from 'globby';
 import path from 'path';
@@ -11,7 +18,7 @@ export function truncate(fileString: string, truncateMarker: RegExp | string) {
 }
 
 // YYYY-MM-DD-{name}.mdx?
-// prefer named capture, but old node version do not support
+// prefer named capture, but old Node version does not support.
 const FILENAME_PATTERN = /^(\d{4}-\d{1,2}-\d{1,2})-?(.*?).mdx?$/;
 
 function toUrl({date, link}: DateLink) {
@@ -93,7 +100,8 @@ export async function generateBlogPosts(
 
   await Promise.all(
     blogFiles.map(async (relativeSource: string) => {
-      // Cannot use path.join() as it resolves '../' and removes the '@site'. Let webpack loader resolve it.
+      // Cannot use path.join() as it resolves '../' and removes the '@site'.
+      // Let webpack loader resolve it.
       const source = path.join(blogDir, relativeSource);
       const aliasedSource = `@site/${path.relative(siteDir, source)}`;
       const blogFileName = path.basename(relativeSource);
@@ -102,7 +110,7 @@ export async function generateBlogPosts(
       const {frontMatter, excerpt} = parse(fileString);
 
       let date;
-      // extract date and title from filename
+      // Extract date and title from filename.
       const match = blogFileName.match(FILENAME_PATTERN);
       let linkName = blogFileName.replace(/\.mdx?$/, '');
       if (match) {
@@ -110,11 +118,11 @@ export async function generateBlogPosts(
         date = new Date(dateString);
         linkName = name;
       }
-      // prefer usedefined date
+      // Prefer user-defined date.
       if (frontMatter.date) {
         date = new Date(frontMatter.date);
       }
-      // use file create time for blog
+      // Use file create time for blog.
       date = date || (await fs.stat(source)).birthtime;
       frontMatter.title = frontMatter.title || linkName;
 
@@ -135,6 +143,7 @@ export async function generateBlogPosts(
       });
     }),
   );
+
   blogPosts.sort(
     (a, b) => b.metadata.date.getTime() - a.metadata.date.getTime(),
   );

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

@@ -4,6 +4,7 @@
  * 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 _ from 'lodash';
 import path from 'path';

packages/docusaurus-theme-classic/src/theme/BlogPostItem/index.js

@@ -14,6 +14,21 @@ import MDXComponents from '@theme/MDXComponents';
 
 import styles from './styles.module.css';
 
+const MONTHS = [
+  'January',
+  'February',
+  'March',
+  'April',
+  'May',
+  'June',
+  'July',
+  'August',
+  'September',
+  'October',
+  'November',
+  'December',
+];
+
 function BlogPostItem(props) {
   const {
     children,
@@ -23,32 +38,20 @@ function BlogPostItem(props) {
     isBlogPostPage = false,
   } = props;
   const {date, permalink, tags} = metadata;
-  const {author, authorURL, authorTitle, authorFBID, title} = frontMatter;
+  const {author, title} = frontMatter;
+
+  const authorURL = frontMatter.author_url || frontMatter.authorURL;
+  const authorTitle = frontMatter.author_title || frontMatter.authorTitle;
+  const authorImageURL =
+    frontMatter.author_image_url || frontMatter.authorImageURL;
 
   const renderPostHeader = () => {
     const TitleHeading = isBlogPostPage ? 'h1' : 'h2';
     const match = date.substring(0, 10).split('-');
     const year = match[0];
-    const month = [
-      'January',
-      'February',
-      'March',
-      'April',
-      'May',
-      'June',
-      'July',
-      'August',
-      'September',
-      'October',
-      'November',
-      'December',
-    ][parseInt(match[1], 10) - 1];
+    const month = MONTHS[parseInt(match[1], 10) - 1];
     const day = parseInt(match[2], 10);
 
-    const authorImageURL = authorFBID
-      ? `https://graph.facebook.com/${authorFBID}/picture/?height=200&width=200`
-      : frontMatter.authorImageURL;
-
     return (
       <header>
         <TitleHeading