Fixed #31570 -- Corrected translation loading for apps providing territorial language variants with different plural equations.

Regression in e3e48b00127c09eafe6439d980a82fc5c591b673.

Thanks to Shai Berger for report, reproduce and suggested fix.

django/utils/translation/trans_real.py

@@ -96,7 +96,7 @@ class TranslationCatalog:
                 cat.update(trans._catalog)
                 break
         else:
-            self._catalogs.insert(0, trans._catalog)
+            self._catalogs.insert(0, trans._catalog.copy())
             self._plurals.insert(0, trans.plural)
 
     def get(self, key, default=None):

docs/releases/2.2.13.txt

@@ -4,9 +4,12 @@ Django 2.2.13 release notes
 
 *Expected June 3, 2020*
 
-Django 2.2.13 fixes two security issues and a bug in 2.2.12.
+Django 2.2.13 fixes two security issues and a regression in 2.2.12.
 
 Bugfixes
 ========
 
-* ...
+* Fixed a regression in Django 2.2.12 that affected translation loading for
+  apps providing translations for territorial language variants as well as a
+  generic language, where the project has different plural equations for the
+  language (:ticket:`31570`).

docs/releases/3.0.7.txt

@@ -25,3 +25,8 @@ Bugfixes
 
 * Fixed a regression in Django 3.0 where all resolved ``Subquery()``
   expressions were considered equal (:ticket:`31607`).
+
+* Fixed a regression in Django 3.0.5 that affected translation loading for apps
+  providing translations for territorial language variants as well as a generic
+  language, where the project has different plural equations for the language
+  (:ticket:`31570`).

tests/i18n/loading/en/LC_MESSAGES/django.po

@@ -0,0 +1,23 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2020-05-13 08:42+0000\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+
+#: trans/tests.py:16
+msgid "local country person"
+msgstr "local country person"

tests/i18n/loading/en_AU/LC_MESSAGES/django.po

@@ -0,0 +1,23 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2020-05-13 08:42+0000\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+
+#: trans/tests.py:16
+msgid "local country person"
+msgstr "aussie"

tests/i18n/loading/en_CA/LC_MESSAGES/django.po

@@ -0,0 +1,22 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2020-05-13 08:42+0000\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+#: trans/tests.py:16
+msgid "local country person"
+msgstr "canuck"

tests/i18n/loading/en_NZ/LC_MESSAGES/django.po

@@ -0,0 +1,22 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2020-05-13 08:42+0000\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+
+#: trans/tests.py:16
+msgid "local country person"
+msgstr "kiwi"

tests/i18n/loading_app/apps.py

@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class LoadingAppConfig(AppConfig):
+    name = 'loading_app'

tests/i18n/loading_app/locale/en/LC_MESSAGES/django.po

@@ -0,0 +1,25 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+#, fuzzy
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2020-05-13 11:39+0300\n"
+"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+
+#: apps.py:8
+msgid ""
+"An app with its own translation files, with one for 'en' but not the "
+"regional dialects of English"
+msgstr ""

tests/i18n/tests.py

@@ -384,6 +384,51 @@ class TranslationTests(SimpleTestCase):
             self.assertIs(get_language_bidi(), True)
 
 
+class TranslationLoadingTests(SimpleTestCase):
+    def setUp(self):
+        """Clear translation state."""
+        self._old_language = get_language()
+        self._old_translations = trans_real._translations
+        deactivate()
+        trans_real._translations = {}
+
+    def tearDown(self):
+        trans_real._translations = self._old_translations
+        activate(self._old_language)
+
+    @override_settings(
+        USE_I18N=True,
+        LANGUAGE_CODE='en',
+        LANGUAGES=[
+            ('en', 'English'),
+            ('en-ca', 'English (Canada)'),
+            ('en-nz', 'English (New Zealand)'),
+            ('en-au', 'English (Australia)'),
+        ],
+        LOCALE_PATHS=[os.path.join(here, 'loading')],
+        INSTALLED_APPS=['i18n.loading_app'],
+    )
+    def test_translation_loading(self):
+        """
+        "loading_app" does not have translations for all languages provided by
+        "loading". Catalogs are merged correctly.
+        """
+        tests = [
+            ('en', 'local country person'),
+            ('en_AU', 'aussie'),
+            ('en_NZ', 'kiwi'),
+            ('en_CA', 'canuck'),
+        ]
+        # Load all relevant translations.
+        for language, _ in tests:
+            activate(language)
+        # Catalogs are merged correctly.
+        for language, nickname in tests:
+            with self.subTest(language=language):
+                activate(language)
+                self.assertEqual(gettext('local country person'), nickname)
+
+
 class TranslationThreadSafetyTests(SimpleTestCase):
 
     def setUp(self):