Fixed #28636 -- Allowed customizing of translation fallback with sett…

…ing LANGUAGE_FALLBACK

Thanks Claude Paroz and Dhia Abbasi for the reviews and good ideas.

django/conf/global_settings.py

@@ -47,6 +47,10 @@ def gettext_noop(s):
 # http://www.i18nguy.com/unicode/language-identifiers.html
 LANGUAGE_CODE = 'en-us'
 
+# Language code for translation fallback, which is LANGUAGE_CODE by default.
+# Set this as fallback for unsupported languages and missing translations.
+LANGUAGE_FALLBACK = LANGUAGE_CODE
+
 # Languages we provide translations for, out of the box.
 LANGUAGES = [
     ('af', gettext_noop('Afrikaans')),

django/middleware/locale.py

@@ -21,7 +21,7 @@ def process_request(self, request):
         language = translation.get_language_from_request(request, check_path=i18n_patterns_used)
         language_from_path = translation.get_language_from_path(request.path_info)
         if not language_from_path and i18n_patterns_used and not prefixed_default_language:
-            language = settings.LANGUAGE_CODE
+            language = translation.get_fallback()
         translation.activate(language)
         request.LANGUAGE_CODE = translation.get_language()
 

django/utils/translation/__init__.py

@@ -189,6 +189,10 @@ def get_language_bidi():
     return _trans.get_language_bidi()
 
 
+def get_fallback():
+    return _trans.get_fallback()
+
+
 def check_for_language(lang_code):
     return _trans.check_for_language(lang_code)
 

django/utils/translation/trans_real.py

@@ -178,16 +178,19 @@ def _add_local_translations(self):
 
     def _add_fallback(self, localedirs=None):
         """Set the GNUTranslations() fallback with the default language."""
-        # Don't set a fallback for the default language or any English variant
+        fallback = get_fallback()
+        # Don't set a fallback for any default language variant or any English variant
         # (as it's empty, so it'll ALWAYS fall back to the default language)
-        if self.__language == settings.LANGUAGE_CODE or self.__language.startswith('en'):
+        # If the language and fallback are the same, there's no need for adding a fallback.
+        if self.__language == fallback or self.__language.startswith(
+                settings.LANGUAGE_CODE[0:2]) or self.__language.startswith('en'):
             return
         if self.domain == 'django':
             # Get from cache
-            default_translation = translation(settings.LANGUAGE_CODE)
+            default_translation = translation(fallback)
         else:
             default_translation = DjangoTranslation(
-                settings.LANGUAGE_CODE, domain=self.domain, localedirs=localedirs
+                fallback, domain=self.domain, localedirs=localedirs
             )
         self.add_fallback(default_translation)
 
@@ -278,6 +281,14 @@ def get_language_bidi():
         return base_lang in settings.LANGUAGES_BIDI
 
 
+def get_fallback():
+    """
+    Return the fallback language for unsupported languages and missing translations.
+    """
+    fallback = settings.LANGUAGE_FALLBACK
+    return fallback if fallback and isinstance(fallback, str) else settings.LANGUAGE_CODE
+
+
 def catalog():
     """
     Return the current active catalog for further processing.
@@ -504,9 +515,9 @@ def get_language_from_request(request, check_path=False):
             continue
 
     try:
-        return get_supported_language_variant(settings.LANGUAGE_CODE)
+        return get_supported_language_variant(get_fallback())
     except LookupError:
-        return settings.LANGUAGE_CODE
+        return get_fallback()
 
 
 def parse_accept_lang_header(lang_string):