feat(v2): implement Google analytics plugin

packages/docusaurus-plugin-google-analytics/src/analytics.js

@@ -0,0 +1,68 @@
+/**
+ * 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 siteConfig from '@generated/docusaurus.config';
+
+const {themeConfig} = siteConfig;
+
+export default (function() {
+  if (!themeConfig.googleAnalytics) {
+    return null;
+  }
+
+  const {trackingID} = themeConfig.googleAnalytics;
+  if (process.env.NODE_ENV === 'development' && !trackingID) {
+    console.warn(
+      'You specified the `googleAnalytics` object in `themeConfig` but the `trackingID` field was missing. ' +
+        'Please ensure this is not a mistake.',
+    );
+    return null;
+  }
+
+  if (
+    // process.env.NODE_ENV !== 'production' || // TODO: Add it back after testing that it works.
+    !trackingID ||
+    typeof window === 'undefined'
+  ) {
+    return null;
+  }
+
+  /* eslint-disable */
+  (function(i, s, o, g, r, a, m) {
+    i['GoogleAnalyticsObject'] = r;
+    (i[r] =
+      i[r] ||
+      function() {
+        (i[r].q = i[r].q || []).push(arguments);
+      }),
+      (i[r].l = 1 * new Date());
+    (a = s.createElement(o)), (m = s.getElementsByTagName(o)[0]);
+    a.async = 1;
+    a.src = g;
+    m.parentNode.insertBefore(a, m);
+  })(
+    window,
+    document,
+    'script',
+    'https://www.google-analytics.com/analytics.js',
+    'ga',
+  );
+  /* eslint-enable */
+
+  window.ga('create', trackingID, 'auto');
+  window.ga('send', 'pageview');
+
+  return {
+    onRouteUpdate({location}) {
+      // Set page so that subsequent hits on this page are attributed
+      // to this page. This is recommended for Single-page Applications.
+      window.ga('set', 'page', location.pathname);
+      // Always refer to the variable on window in-case it gets overridden elsewhere.
+      window.ga('send', 'pageview');
+    },
+  };
+})();

packages/docusaurus-plugin-google-analytics/src/index.js

@@ -0,0 +1,18 @@
+/**
+ * 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 path = require('path');
+
+module.exports = function() {
+  return {
+    name: 'docusaurus-plugin-google-analytics',
+
+    getClientModules() {
+      return [path.resolve(__dirname, './analytics')];
+    },
+  };
+};