Add experimental react support within markdown

Also added fronmatter for interactive: true to turn on React on a file by file
basis and prevent slowing down the builds for non-react files

content/github/getting-started-with-github/access-permissions-on-github.md

@@ -9,6 +9,7 @@ intro: 'While you can grant read/write access to collaborators on a personal rep
 versions:
   free-pro-team: '*'
   enterprise-server: '*'
+interactive: true
 ---
 
 ### Personal user accounts
@@ -17,16 +18,31 @@ A repository owned by a user account has two permission levels: the *repository
 
 ### Organization accounts
 
+<!--react-->
+<BlueContent>
+
+Hello world!
+
+</BlueContent>
+<!--end-react-->
+
 Organization members can have *owner*{% if currentVersion == "free-pro-team@latest" %}, *billing manager*,{% endif %} or *member* roles. Owners have complete administrative access to your organization{% if currentVersion == "free-pro-team@latest" %}, while billing managers can manage billing settings{% endif %}. Member is the default role for everyone else. You can manage access permissions for multiple members at a time with teams. For more information, see:
 - "[Permission levels for an organization](/articles/permission-levels-for-an-organization)"
 - "[Project board permissions for an organization](/articles/project-board-permissions-for-an-organization)"
 - "[Repository permission levels for an organization](/articles/repository-permission-levels-for-an-organization)"
 - "[About teams](/articles/about-teams)"
 
+<!--react--><BlueContent>More blue content!</BlueContent><!--end-react-->
+
+<!--react--><RedContent>Red content!</RedContent><!--end-react-->
+
+<!--react--><Timer /><!--end-react-->
+
 {% if currentVersion == "free-pro-team@latest" %}
 
 ### Enterprise accounts
 
+
 *Enterprise owners* have ultimate power over the enterprise account and can take every action in the enterprise account. *Billing managers* can manage your enterprise account's billing settings. Members and outside collaborators of organizations owned by your enterprise account are automatically members of the enterprise account, although they have no access to the enterprise account itself or its settings. For more information, see "[Roles for an enterprise account](/articles/roles-for-an-enterprise-account)."
 
 {% data reusables.gated-features.enterprise-accounts %}

includes/head.html

@@ -26,4 +26,6 @@
   <link rel="stylesheet" href="/dist/index.css">
   <link rel="alternate icon" type="image/png" href="/assets/images/site/favicon.png">
   <link rel="icon" type="image/svg+xml" href="/assets/images/site/favicon.svg">
+  <script src="/assets/js/react.development.js" crossorigin></script>
+  <script src="/assets/js/react-dom.development.js" crossorigin></script>
 </head>

lib/frontmatter.js

@@ -70,6 +70,9 @@ const schema = {
         quickstart: { type: 'string' },
         learn: { type: 'string' }
       }
+    },
+    interactive: {
+      type: 'boolean'
     }
   }
 }

lib/page.js

@@ -15,10 +15,12 @@ const pathUtils = require('./path-utils')
 const Permalink = require('./permalink')
 const languages = require('./languages')
 const renderContent = require('./render-content')
+const renderReact = require('./react-engine')
 const frontmatter = require('./frontmatter')
 const products = require('./all-products')
 const slash = require('slash')
 
+
 class Page {
   constructor (opts) {
     assert(opts.relativePath, 'relativePath is required')
@@ -119,9 +121,30 @@ class Page {
     this.title = await renderContent(this.rawTitle, context, { textOnly: true, encodeEntities: true })
     this.shortTitle = await renderContent(this.shortTitle, context, { textOnly: true, encodeEntities: true })
 
-    const markdown = this.mapTopic
+    let markdown = this.mapTopic
       ? getMapTopicContent(this, context.pages, context.redirects)
       : this.markdown
+
+    // If the article is interactive parse the React!
+    if (this.interactive) {
+      // Search for the react code comments to find the react components
+      const reactComponents = markdown.match(/<!--react-->(.*?)<!--end-react-->/gms)
+
+      // Render each of the react components in the Markdown
+      for (const index in reactComponents) {
+        let componentStr = reactComponents[index]
+
+        // Remove the React comment indicators
+        componentStr = componentStr.replace('<!--react-->\n', '').replace('<!--react-->', '')
+        componentStr = componentStr.replace('\n<!--end-react-->', '').replace('<!--end-react-->', '')
+
+        // Get the rendered component
+        const renderedComponent = await renderReact(componentStr)
+
+        // Replace the react component with the rendered html
+        markdown = markdown.replace(reactComponents[index], renderedComponent)
+      }
+    }
 
     const html = await renderContent(markdown, context)
 

lib/react-engine.js

@@ -0,0 +1,49 @@
+const babel = require('@babel/core')
+const React = require('react')
+const { renderToString } = require('react-dom/server')
+const mdx = require('@mdx-js/mdx')
+const { MDXProvider, mdx: createElement } = require('@mdx-js/react')
+const BlueContent = require('../dist/react/BlueContent')
+const RedContent = require('../dist/react/RedContent')
+const Timer = require('../dist/react/Timer')
+
+const transform = code =>
+  babel.transform(code, {
+    plugins: [
+      '@babel/plugin-transform-react-jsx',
+      '@babel/plugin-proposal-object-rest-spread'
+    ]
+  }).code
+
+const renderReact = async componentStr => {
+  const jsx = await mdx(componentStr, { skipExport: true })
+  const component = transform(jsx)
+  const scope = { mdx: createElement }
+
+  /* eslint-disable-next-line */
+  const fn = new Function(
+    'React',
+    ...Object.keys(scope),
+    `${component}; return React.createElement(MDXContent)`
+  )
+
+  const element = fn(React, ...Object.values(scope))
+
+  // All components that we want accessible to markdown files must
+  // be registered here
+  const components = {
+    BlueContent,
+    RedContent,
+    Timer
+  }
+
+  const elementWithProvider = React.createElement(
+    MDXProvider,
+    { components },
+    element
+  )
+
+  return renderToString(elementWithProvider)
+}
+
+module.exports = renderReact