[1.10.x] Fixed #27063 -- Prevented i18n_patterns() from using too much of the URL as the language.

Backport of a01d887a3a from master

django/utils/translation/trans_real.py

@@ -48,7 +48,7 @@ language_code_re = re.compile(
     re.IGNORECASE
 )
 
-language_code_prefix_re = re.compile(r'^/([\w@-]+)(/|$)')
+language_code_prefix_re = re.compile(r'^/(\w+([@-]\w+)?)(/|$)')
 
 
 @receiver(setting_changed)

docs/releases/1.10.3.txt

@@ -23,3 +23,6 @@ Bugfixes
 
 * Fixed ``QuerySet.bulk_create()`` on PostgreSQL when the number of objects is
   a multiple plus one of ``batch_size`` (:ticket:`27385`).
+
+* Prevented ``i18n_patterns()`` from using too much of the URL as the language
+  to fix a use case for ``prefix_default_language=False`` (:ticket:`27063`).

tests/i18n/tests.py

@@ -1474,6 +1474,7 @@ class MiscTests(SimpleTestCase):
         self.assertEqual(g('/de/'), 'de')
         self.assertEqual(g('/de-at/'), 'de-at')
         self.assertEqual(g('/de-ch/'), 'de')
+        self.assertIsNone(g('/de-simple-page/'))
 
     def test_get_language_from_path_null(self):
         from django.utils.translation.trans_null import get_language_from_path as g
@@ -1806,6 +1807,7 @@ class LocaleMiddlewareTests(TestCase):
     USE_I18N=True,
     LANGUAGES=[
         ('en', 'English'),
+        ('de', 'German'),
         ('fr', 'French'),
     ],
     MIDDLEWARE=[
@@ -1836,6 +1838,11 @@ class UnprefixedDefaultLanguageTests(SimpleTestCase):
         with self.assertRaisesMessage(AssertionError, "Unexpected kwargs for i18n_patterns(): {'foo':"):
             i18n_patterns(object(), foo='bar')
 
+    def test_page_with_dash(self):
+        # A page starting with /de* shouldn't match the 'de' langauge code.
+        response = self.client.get('/de-simple-page/')
+        self.assertEqual(response.content, b'Yes')
+
 
 @override_settings(
     USE_I18N=True,

tests/i18n/urls_default_unprefixed.py

@@ -4,6 +4,7 @@ from django.http import HttpResponse
 from django.utils.translation import ugettext_lazy as _
 
 urlpatterns = i18n_patterns(
+    url(r'^(?P<arg>[\w-]+)-page', lambda request, **arg: HttpResponse(_("Yes"))),
     url(r'^simple/$', lambda r: HttpResponse(_("Yes"))),
     prefix_default_language=False,
 )