Fix sphinx_rtd_theme theme override in embed js

The last refactor wasn't aware of the fact that the js Build class was
modifying the actual config object in place. We are fixing this by using a
getter method were the value is needed and are not mutating the original config
object in place.

Fixes #1542.

Author: gregmuellegger

readthedocs/core/static-src/core/js/doc-embed/build.js

@@ -1,4 +1,3 @@
-var Build = require('./build').Build;
 var rtddata = require('./rtd-data');
 var versionCompare = require('./version-compare');
 
@@ -10,7 +9,7 @@ function init() {
         project: rtd['project'],
         version: rtd['version'],
         page: rtd['page'],
-        theme: rtd['theme'],
+        theme: rtd.get_theme_name(),
         format: "jsonp",
     };
 
@@ -50,11 +49,11 @@ function init() {
 
 
 function injectFooter(data) {
-    var build = new Build(rtddata.get());
+    var config = rtddata.get();
 
     // If the theme looks like ours, update the existing badge
     // otherwise throw a a full one into the page.
-    if (build.is_rtd_theme()) {
+    if (config.is_rtd_theme()) {
         $("div.rst-other-versions").html(data['html']);
     } else {
         $("body").append(data['html']);
@@ -67,7 +66,7 @@ function injectFooter(data) {
     }
 
     // Show promo selectively
-    if (data.promo && build.show_promo()) {
+    if (data.promo && config.show_promo()) {
         var promo = new sponsorship.Promo(
             data.promo_data.id,
             data.promo_data.text,

readthedocs/core/static-src/core/js/doc-embed/footer.js

@@ -5,14 +5,50 @@
  */
 
 
+var configMethods = {
+    is_rtd_theme: function () {
+        return this.get_theme_name() === 'sphinx_rtd_theme';
+    },
+
+    is_sphinx_builder: function () {
+        return (!('builder' in this) || this.builder != 'mkdocs');
+    },
+
+    get_theme_name: function () {
+        // Crappy heuristic, but people change the theme name on us.  So we have to
+        // do some duck typing.
+        if (this.theme !== 'sphinx_rtd_theme') {
+            if ($('div.rst-other-versions').length === 1) {
+                return 'sphinx_rtd_theme';
+            }
+        }
+        return this.theme;
+    },
+
+    show_promo: function () {
+        return (
+            this.api_host !== 'https://readthedocs.com' &&
+            this.is_sphinx_builder() &&
+            this.is_rtd_theme());
+    }
+};
+
+
 /*
  * Access READTHEDOCS_DATA on call, not on module load. The reason is that the
  * READTHEDOCS_DATA might not be available during script load time.
  */
 function get() {
-    return $.extend({
+    // Make `methods` the prototype.
+    var config = Object.create(configMethods);
+
+    var defaults = {
         api_host: 'https://readthedocs.org'
-    }, window.READTHEDOCS_DATA);
+    };
+
+    $.extend(config, defaults, window.READTHEDOCS_DATA);
+
+    return config;
 }