Added support for gtag (#1129)

* Added support for gtag

* Fix missing curly braces

* Simplify gtag script import

* Fix tag

* Add gtag to docs

Co-authored-by: Aaron Carlisle <[email protected]>

Author: ThomasTNO

docs/configuring.rst

@@ -13,7 +13,7 @@ For example:
 .. code:: python
 
     html_theme_options = {
-        'analytics_id': 'UA-XXXXXXX-1',  #  Provided by Google in your dashboard
+        'analytics_id': 'G-XXXXXXXXXX',  #  Provided by Google in your dashboard
         'analytics_anonymize_ip': False,
         'logo_only': False,
         'display_version': True,
@@ -96,11 +96,13 @@ Miscellaneous options
 
 .. confval:: analytics_id
 
-    If specified, Google Analytics' javascript is included in your pages.
-    Set the value to the ID provided to you by google (like ``UA-XXXXXXX``).
+    If specified, Google Analytics' `gtag.js`_ is included in your pages.
+    Set the value to the ID provided to you by google (like ``UA-XXXXXXX`` or ``G-XXXXXXXXXX``).
 
     :type: string
 
+    .. _gtag.js: https://developers.google.com/gtagjs
+
 .. confval:: analytics_anonymize_ip
 
     Anonymize visitor IP addresses in Google Analytics.

sphinx_rtd_theme/layout.html

@@ -219,17 +219,15 @@
   {%- if not READTHEDOCS %}
     {%- if theme_analytics_id %}
     <!-- Theme Analytics -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id={{ theme_analytics_id }}"></script>
     <script>
-    (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');
-
-    ga('create', '{{ theme_analytics_id }}', 'auto');
-    {%- if theme_analytics_anonymize_ip|tobool %}
-    ga('set', 'anonymizeIp', true);
-    {%- endif %}
-    ga('send', 'pageview');
+      window.dataLayer = window.dataLayer || [];
+      function gtag(){dataLayer.push(arguments);}
+      gtag('js', new Date());
+
+      gtag('config', '{{ theme_analytics_id }}', {
+          'anonymize_ip': {{ 'true' if theme_analytics_anonymize_ip|tobool else 'false' }},
+      });
     </script>
 
     {%- endif %}