[1.8.x] Fixed #24515 -- Fixed DjangoTranslation plural handling

Backport of 9e83f30cd3 from master.

django/utils/translation/trans_real.py

@@ -111,7 +111,6 @@ class DjangoTranslation(gettext_module.GNUTranslations):
         self.__language = language
         self.__to_language = to_language(language)
         self.__locale = to_locale(language)
-        self.plural = lambda n: int(n != 1)
 
         self._init_translation_catalog()
         self._add_installed_apps_translations()
@@ -139,6 +138,7 @@ class DjangoTranslation(gettext_module.GNUTranslations):
             # provides merge support for NullTranslations()
             translation._catalog = {}
             translation._info = {}
+            translation.plural = lambda n: int(n != 1)
         return translation
 
     def _init_translation_catalog(self):
@@ -151,6 +151,7 @@ class DjangoTranslation(gettext_module.GNUTranslations):
             # gettext will raise an IOError (refs #18192).
             use_null_fallback = False
         translation = self._new_gnu_trans(localedir, use_null_fallback)
+        self.plural = translation.plural
         self._info = translation._info.copy()
         self._catalog = translation._catalog.copy()
 

tests/i18n/tests.py

@@ -29,7 +29,7 @@ from django.utils.translation import (
     get_language, get_language_from_request, get_language_info, gettext,
     gettext_lazy, ngettext_lazy, npgettext, npgettext_lazy, pgettext,
     pgettext_lazy, string_concat, to_locale, trans_real, ugettext,
-    ugettext_lazy, ungettext_lazy,
+    ugettext_lazy, ungettext, ungettext_lazy,
 )
 
 from .forms import CompanyForm, I18nForm, SelectDateForm, SelectDateWidget
@@ -56,6 +56,16 @@ def patch_formats(lang, **settings):
 
 class TranslationTests(TestCase):
 
+    @translation.override('fr')
+    def test_plural(self):
+        """
+        Test plurals with ungettext. French differs from English in that 0 is singular.
+        """
+        self.assertEqual(ungettext("%d year", "%d years", 0) % 0, "0 année")
+        self.assertEqual(ungettext("%d year", "%d years", 2) % 2, "2 années")
+        self.assertEqual(ungettext("%(size)d byte", "%(size)d bytes", 0) % {'size': 0}, "0 octet")
+        self.assertEqual(ungettext("%(size)d byte", "%(size)d bytes", 2) % {'size': 2}, "2 octets")
+
     def test_override(self):
         activate('de')
         try: