refactor(v2): shift to docusaurus/mdx-loader (#1339)

packages/docusaurus-mdx-loader/src/index.js

@@ -0,0 +1,38 @@
+/**
+ * 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.
+ */
+const {getOptions} = require('loader-utils');
+const mdx = require('@mdx-js/mdx');
+const rehypePrism = require('@mapbox/rehype-prism');
+
+const DEFAULT_OPTIONS = {
+  rehypePlugins: [[rehypePrism, {ignoreMissing: true}]],
+  prismTheme: 'prism-themes/themes/prism-atom-dark.css',
+};
+
+module.exports = async function(content) {
+  const callback = this.async();
+
+  const options = Object.assign(DEFAULT_OPTIONS, getOptions(this), {
+    filepath: this.resourcePath,
+  });
+  let result;
+
+  try {
+    result = await mdx(content, options);
+  } catch (err) {
+    return callback(err);
+  }
+
+  const code = `
+  import React from 'react';
+  import { mdx } from '@mdx-js/react';
+  import '${options.prismTheme}';
+  ${result}
+  `;
+
+  return callback(null, code);
+};