The language option now has a clearly defined fallback chain

src/js/select2/defaults.js

@@ -232,66 +232,29 @@ define([
       );
     }
 
-    if (typeof options.language === 'string') {
-      // Check if the language is specified with a region
-      if (options.language.indexOf('-') > 0) {
-        // Extract the region information if it is included
-        var languageParts = options.language.split('-');
-        var baseLanguage = languageParts[0];
-
-        options.language = [options.language, baseLanguage];
-      } else {
-        options.language = [options.language];
-      }
-    }
-
-    if ($.isArray(options.language)) {
-      var languages = new Translation();
-      options.language.push('en');
-
-      var languageNames = options.language;
+    // If the defaults were not previously applied from an element, it is
+    // possible for the language option to have not been resolved
+    options.language = this._resolveLanguage(options.language);
 
-      for (var l = 0; l < languageNames.length; l++) {
-        var name = languageNames[l];
-        var language = {};
+    // Always fall back to English since it will always be complete
+    options.language.push('en');
 
-        try {
-          // Try to load it with the original name
-          language = Translation.loadPath(name);
-        } catch (e) {
-          try {
-            // If we couldn't load it, check if it wasn't the full path
-            name = this.defaults.amdLanguageBase + name;
-            language = Translation.loadPath(name);
-          } catch (ex) {
-            // The translation could not be loaded at all. Sometimes this is
-            // because of a configuration problem, other times this can be
-            // because of how Select2 helps load all possible translation files.
-            if (options.debug && window.console && console.warn) {
-              console.warn(
-                'Select2: The language file for "' + name + '" could not be ' +
-                'automatically loaded. A fallback will be used instead.'
-              );
-            }
+    var uniqueLanguages = [];
 
-            continue;
-          }
-        }
+    for (var l = 0; l < options.language.length; l++) {
+      var language = options.language[l];
 
-        languages.extend(language);
+      if (uniqueLanguages.indexOf(language) === -1) {
+        uniqueLanguages.push(language);
       }
+    }
 
-      options.translations = languages;
-    } else {
-      var baseTranslation = Translation.loadPath(
-        this.defaults.amdLanguageBase + 'en'
-      );
-      var customTranslation = new Translation(options.language);
-
-      customTranslation.extend(baseTranslation);
+    options.language = uniqueLanguages;
 
-      options.translations = customTranslation;
-    }
+    options.translations = this._processTranslations(
+      options.language,
+      options.debug
+    );
 
     return options;
   };
@@ -358,7 +321,7 @@ define([
       debug: false,
       dropdownAutoWidth: false,
       escapeMarkup: Utils.escapeMarkup,
-      language: EnglishTranslation,
+      language: {},
       matcher: matcher,
       minimumInputLength: 0,
       maximumInputLength: 0,
@@ -380,6 +343,103 @@ define([
     };
   };
 
+  Defaults.prototype.applyFromElement = function (options, $element) {
+    var optionLanguage = options.language;
+    var defaultLanguage = this.defaults.language;
+    var elementLanguage = $element.prop('lang');
+    var parentLanguage = $element.closest('[lang]').prop('lang');
+
+    var languages = Array.prototype.concat.call(
+      this._resolveLanguage(elementLanguage),
+      this._resolveLanguage(optionLanguage),
+      this._resolveLanguage(defaultLanguage),
+      this._resolveLanguage(parentLanguage)
+    );
+
+    options.language = languages;
+
+    return options;
+  };
+
+  Defaults.prototype._resolveLanguage = function (language) {
+    if (!language) {
+      return [];
+    }
+
+    if ($.isEmptyObject(language)) {
+      return [];
+    }
+
+    if ($.isPlainObject(language)) {
+      return [language];
+    }
+
+    var languages;
+
+    if (!$.isArray(language)) {
+      languages = [language];
+    } else {
+      languages = language;
+    }
+
+    var resolvedLanguages = [];
+
+    for (var l = 0; l < languages.length; l++) {
+      resolvedLanguages.push(languages[l]);
+
+      if (typeof languages[l] === 'string' && languages[l].indexOf('-') > 0) {
+        // Extract the region information if it is included
+        var languageParts = languages[l].split('-');
+        var baseLanguage = languageParts[0];
+
+        resolvedLanguages.push(baseLanguage);
+      }
+    }
+
+    return resolvedLanguages;
+  };
+
+  Defaults.prototype._processTranslations = function (languages, debug) {
+    var translations = new Translation();
+
+    for (var l = 0; l < languages.length; l++) {
+      var languageData = new Translation();
+
+      var language = languages[l];
+
+      if (typeof language === 'string') {
+        try {
+          // Try to load it with the original name
+          languageData = Translation.loadPath(language);
+        } catch (e) {
+          try {
+            // If we couldn't load it, check if it wasn't the full path
+            language = this.defaults.amdLanguageBase + language;
+            languageData = Translation.loadPath(language);
+          } catch (ex) {
+            // The translation could not be loaded at all. Sometimes this is
+            // because of a configuration problem, other times this can be
+            // because of how Select2 helps load all possible translation files
+            if (debug && window.console && console.warn) {
+              console.warn(
+                'Select2: The language file for "' + language + '" could ' +
+                'not be automatically loaded. A fallback will be used instead.'
+              );
+            }
+          }
+        }
+      } else if ($.isPlainObject(language)) {
+        languageData = new Translation(language);
+      } else {
+        languageData = language;
+      }
+
+      translations.extend(languageData);
+    }
+
+    return translations;
+  };
+
   Defaults.prototype.set = function (key, value) {
     var camelKey = $.camelCase(key);
 

src/js/select2/options.js

@@ -11,6 +11,10 @@ define([
       this.fromElement($element);
     }
 
+    if ($element != null) {
+      this.options = Defaults.applyFromElement(this.options, $element);
+    }
+
     this.options = Defaults.apply(this.options);
 
     if ($element && $element.is('input')) {
@@ -34,14 +38,6 @@ define([
       this.options.disabled = $e.prop('disabled');
     }
 
-    if (this.options.language == null) {
-      if ($e.prop('lang')) {
-        this.options.language = $e.prop('lang').toLowerCase();
-      } else if ($e.closest('[lang]').prop('lang')) {
-        this.options.language = $e.closest('[lang]').prop('lang');
-      }
-    }
-
     if (this.options.dir == null) {
       if ($e.prop('dir')) {
         this.options.dir = $e.prop('dir');