Fixes #19763 - LocaleMiddleware should check for supported languages in settings.LANGUAGE_CODE

AUTHORS

@@ -328,6 +328,7 @@ answer newbie questions, and generally made Django that much better:
     Denis Kuzmichyov <kuzmichyov@gmail.com>
     Panos Laganakos <panos.laganakos@gmail.com>
     Nick Lane <nick.lane.au@gmail.com>
+    Łukasz Langa <lukasz@langa.pl>
     Stuart Langridge <http://www.kryogenix.org/>
     Paul Lanier <planier@google.com>
     David Larlet <http://david.larlet.fr>

django/utils/translation/__init__.py

@@ -187,10 +187,10 @@ def get_language_info(lang_code):
     try:
         return LANG_INFO[lang_code]
     except KeyError:
-        if '-' in lang_code:
-            splited_lang_code = lang_code.split('-')[0]
-            try:
-                return LANG_INFO[splited_lang_code]
-            except KeyError:
-                raise KeyError("Unknown language code %s and %s." % (lang_code, splited_lang_code))
+        if '-' not in lang_code:
             raise KeyError("Unknown language code %s." % lang_code)
+        generic_lang_code = lang_code.split('-')[0]
+        try:
+            return LANG_INFO[generic_lang_code]
+        except KeyError:
+            raise KeyError("Unknown language code %s and %s." % (lang_code, generic_lang_code))

django/utils/translation/trans_real.py

@@ -356,6 +356,20 @@ def check_for_language(lang_code):
             return True
     return False
 
+def get_supported_language_variant(lang_code, supported=None):
+    """
+    Returns the language-code that's listed in supported languages, possibly
+    selecting a more generic variant. Raises LookupError if nothing found.
+    """
+    if supported is None:
+        from django.conf import settings
+        supported = dict(settings.LANGUAGES)
+    if lang_code and lang_code not in supported:
+        lang_code = lang_code.split('-')[0] # e.g. if fr-ca is not supported fallback to fr
+    if lang_code and lang_code in supported and check_for_language(lang_code):
+        return lang_code
+    raise LookupError(lang_code)
+
 def get_language_from_path(path, supported=None):
     """
     Returns the language-code if there is a valid language-code
@@ -396,11 +410,10 @@ def get_language_from_request(request, check_path=False):
 
     lang_code = request.COOKIES.get(settings.LANGUAGE_COOKIE_NAME)
 
-    if lang_code and lang_code not in supported:
-        lang_code = lang_code.split('-')[0] # e.g. if fr-ca is not supported fallback to fr
-
-    if lang_code and lang_code in supported and check_for_language(lang_code):
-        return lang_code
+    try:
+        return get_supported_language_variant(lang_code, supported)
+    except LookupError:
+        pass
 
     accept = request.META.get('HTTP_ACCEPT_LANGUAGE', '')
     for accept_lang, unused in parse_accept_lang_header(accept):
@@ -434,6 +447,9 @@ def get_language_from_request(request, check_path=False):
                     _accepted[normalized] = lang
                     return lang
 
+    try:
+        return get_supported_language_variant(settings.LANGUAGE_CODE, supported)
+    except LookupError:
         return settings.LANGUAGE_CODE
 
 dot_re = re.compile(r'\S')

tests/regressiontests/i18n/patterns/tests.py

@@ -19,7 +19,7 @@ from django.utils import translation
     TEMPLATE_DIRS=(
         os.path.join(os.path.dirname(upath(__file__)), 'templates'),
     ),
-    LANGUAGE_CODE='en',
+    LANGUAGE_CODE='en-us',
     LANGUAGES=(
         ('nl', 'Dutch'),
         ('en', 'English'),
@@ -171,6 +171,14 @@ class URLRedirectTests(URLTestCaseBase):
         response = self.client.get(response['location'])
         self.assertEqual(response.status_code, 200)
 
+    def test_pl_pl_redirect(self):
+        # language from outside of the supported LANGUAGES list
+        response = self.client.get('/account/register/', HTTP_ACCEPT_LANGUAGE='pl-pl')
+        self.assertRedirects(response, '/en/account/register/')
+
+        response = self.client.get(response['location'])
+        self.assertEqual(response.status_code, 200)
+
 
 class URLVaryAcceptLanguageTests(URLTestCaseBase):
     """

tests/regressiontests/i18n/tests.py

@@ -958,7 +958,7 @@ class TestLanguageInfo(TestCase):
         self.assertEqual(li['bidi'], False)
 
     def test_unknown_language_code(self):
-        six.assertRaisesRegex(self, KeyError, "Unknown language code '?xx'?.", get_language_info, 'xx-xx')
+        six.assertRaisesRegex(self, KeyError, r"Unknown language code xx\.", get_language_info, 'xx')
 
     def test_unknown_only_country_code(self):
         li = get_language_info('de-xx')
@@ -968,7 +968,7 @@ class TestLanguageInfo(TestCase):
         self.assertEqual(li['bidi'], False)
 
     def test_unknown_language_code_and_country_code(self):
-        six.assertRaisesRegex(self, KeyError, "Unknown language code '?xx-xx'? and '?xx'?.", get_language_info, 'xx-xx')
+        six.assertRaisesRegex(self, KeyError, r"Unknown language code xx-xx and xx\.", get_language_info, 'xx-xx')
 
 
 class MultipleLocaleActivationTests(TestCase):