Added custom remark transform for Codepen example links

content/docs/components-and-props.md

@@ -76,7 +76,7 @@ ReactDOM.render(
 );
 ```
 
-<a href="/codepen/components-and-props/rendering-a-component" target="_blank">Try it on CodePen</a>.
+[](codepen://components-and-props/rendering-a-component).
 
 Let's recap what happens in this example:
 
@@ -118,7 +118,7 @@ ReactDOM.render(
 );
 ```
 
-<a href="/codepen/components-and-props/composing-components" target="_blank">Try it on CodePen</a>.
+[](codepen://components-and-props/composing-components).
 
 Typically, new React apps have a single `App` component at the very top. However, if you integrate React into an existing app, you might start bottom-up with a small component like `Button` and gradually work your way to the top of the view hierarchy.
 
@@ -152,7 +152,7 @@ function Comment(props) {
 }
 ```
 
-<a href="/codepen/components-and-props/extracting-components" target="_blank">Try it on CodePen</a>.
+[](codepen://components-and-props/extracting-components).
 
 It accepts `author` (an object), `text` (a string), and `date` (a date) as props, and describes a comment on a social media website.
 
@@ -231,7 +231,7 @@ function Comment(props) {
 }
 ```
 
-<a href="/codepen/components-and-props/extracting-components-continued" target="_blank">Try it on CodePen</a>.
+[](codepen://components-and-props/extracting-components-continued).
 
 Extracting components might seem like grunt work at first, but having a palette of reusable components pays off in larger apps. A good rule of thumb is that if a part of your UI is used several times (`Button`, `Panel`, `Avatar`), or is complex enough on its own (`App`, `FeedStory`, `Comment`), it is a good candidate to be a reusable component.
 

content/docs/hello-world.md

@@ -12,7 +12,7 @@ redirect_from:
   - "docs/getting-started-zh-CN.html"
 ---
 
-The easiest way to get started with React is to use <a href="/codepen/hello-world" target="_blank">this Hello World example code on CodePen</a>. You don't need to install anything; you can just open it in another tab and follow along as we go through examples. If you'd rather use a local development environment, check out the [Installation](/docs/installation.html) page.
+The easiest way to get started with React is to use [this Hello World example code on CodePen](codepen://hello-world). You don't need to install anything; you can just open it in another tab and follow along as we go through examples. If you'd rather use a local development environment, check out the [Installation](/docs/installation.html) page.
 
 The smallest React example looks like this:
 

content/docs/introducing-jsx.md

@@ -46,7 +46,7 @@ ReactDOM.render(
 );
 ```
 
-<a href="/codepen/introducing-jsx" target="_blank">Try it on CodePen.</a>
+[](codepen://introducing-jsx).
 
 We split JSX over multiple lines for readability. While it isn't required, when doing this, we also recommend wrapping it in parentheses to avoid the pitfalls of [automatic semicolon insertion](http://stackoverflow.com/q/2846283).
 

gatsby-config.js

@@ -56,6 +56,7 @@ module.exports = {
             },
           },
           'gatsby-remark-autolink-headers',
+          'gatsby-remark-codepen-examples',
           'gatsby-remark-use-jsx',
           {
             resolve: 'gatsby-remark-prismjs',

package.json

@@ -85,6 +85,7 @@
   },
   "devDependencies": {
     "eslint-config-prettier": "^2.6.0",
-    "recursive-readdir": "^2.2.1"
+    "recursive-readdir": "^2.2.1",
+    "unist-util-map": "^1.0.3"
   }
 }

plugins/gatsby-remark-codepen-examples/index.js

@@ -0,0 +1,57 @@
+const {existsSync} = require('fs');
+const {join} = require('path');
+const map = require('unist-util-map');
+
+const CODEPEN_PROTOCOL = 'codepen://';
+const DEFAULT_LINK_TEXT = 'Try it on CodePen';
+
+// TODO target="_blank"
+module.exports = ({markdownAST}) => {
+  map(markdownAST, (node, index, parent) => {
+    // eg convert
+    // from: [](codepen:introducing-jsx)
+    // to: <a href="/codepen/introducing-jsx" target="_blank">Try it on CodePen</a>
+    // from: [Try the Hello World example on CodePen](codepen:hello-world)
+    // to: <a href="/codepen/hello-world" target="_blank">Try the Hello World example on CodePen</a>
+    if (node.type === 'link' && node.url.startsWith(CODEPEN_PROTOCOL)) {
+      const href = node.url.replace(CODEPEN_PROTOCOL, '/codepen/');
+      const text =
+        node.children.length === 0 ? DEFAULT_LINK_TEXT : node.children[0].value;
+
+      // Verify that the specified example file exists.
+      const filePath = join(__dirname, `../../${href}.js`);
+      if (!existsSync(filePath)) {
+        console.error(
+          `Invalid Codepen link specified; no such file "${filePath}"`,
+        );
+        process.exit(1);
+      }
+
+      const anchorOpenNode = {
+        type: 'html',
+        value: `<a href="${href}" target="_blank">`,
+      };
+
+      const textNode = {
+        type: 'text',
+        value: text,
+      };
+
+      const anchorCloseNode = {
+        type: 'html',
+        value: '</a>',
+      };
+
+      parent.children.splice(
+        index,
+        1,
+        anchorOpenNode,
+        textNode,
+        anchorCloseNode,
+      );
+    }
+
+    // No change
+    return node;
+  });
+};

plugins/gatsby-remark-codepen-examples/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "gatsby-remark-codepen-examples",
+  "version": "0.0.1"
+}

yarn.lock

@@ -9795,6 +9795,12 @@ unist-util-is@^2.0.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/unist-util-is/-/unist-util-is-2.1.1.tgz#0c312629e3f960c66e931e812d3d80e77010947b"
 
+unist-util-map@^1.0.3:
+  version "1.0.3"
+  resolved "https://registry.yarnpkg.com/unist-util-map/-/unist-util-map-1.0.3.tgz#26a913d7cddb3cd3e9a886d135d37a3d1f54e514"
+  dependencies:
+    object-assign "^4.0.1"
+
 unist-util-modify-children@^1.0.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/unist-util-modify-children/-/unist-util-modify-children-1.1.1.tgz#66d7e6a449e6f67220b976ab3cb8b5ebac39e51d"