Fixed #31570 -- Corrected translation loading for apps providing only a subset of supported languages.issue/31570

Regression in e3e48b00127c09eafe6439d980a82fc5c591b673

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

23 files changed, 173 insertions, 3 deletions

diff --git a/django/utils/translation/trans_real.py b/django/utils/translation/trans_real.py
index eed4705f6e..8042f6fdc4 100644
--- a/django/utils/translation/trans_real.py
+++ b/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):
diff --git a/docs/releases/2.2.13.txt b/docs/releases/2.2.13.txt
index 450f7acdbf..9555d40f7b 100644
--- a/docs/releases/2.2.13.txt
+++ b/docs/releases/2.2.13.txt
@@ -4,9 +4,11 @@ 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 only a subset of all supported languages
+  (:ticket:`31570`).
diff --git a/docs/releases/3.0.7.txt b/docs/releases/3.0.7.txt
index c7bc3730fd..3dd2f911c9 100644
--- a/docs/releases/3.0.7.txt
+++ b/docs/releases/3.0.7.txt
@@ -25,3 +25,7 @@ Bugfixes
 
 * Fixed a regression in Django 3.0 where all resolved ``Subquery()``
   expressions were considered equal (:ticket:`31607`).
+
+* Fixed a regression in Django 2.2.12 that affected translation loading for
+  apps providing translations for only a subset of all supported languages
+  (:ticket:`31570`).
diff --git a/tests/i18n/loading/__init__.py b/tests/i18n/loading/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading/__init__.py
diff --git a/tests/i18n/loading/en/LC_MESSAGES/django.mo b/tests/i18n/loading/en/LC_MESSAGES/django.mo
new file mode 100644
index 0000000000..f666550adb
--- /dev/null
+++ b/tests/i18n/loading/en/LC_MESSAGES/django.mo
diff --git a/tests/i18n/loading/en/LC_MESSAGES/django.po b/tests/i18n/loading/en/LC_MESSAGES/django.po
new file mode 100644
index 0000000000..d43d83e34a
--- /dev/null
+++ b/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"
diff --git a/tests/i18n/loading/en/__init__.py b/tests/i18n/loading/en/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading/en/__init__.py
diff --git a/tests/i18n/loading/en_AU/LC_MESSAGES/django.mo b/tests/i18n/loading/en_AU/LC_MESSAGES/django.mo
new file mode 100644
index 0000000000..98b016bc6c
--- /dev/null
+++ b/tests/i18n/loading/en_AU/LC_MESSAGES/django.mo
diff --git a/tests/i18n/loading/en_AU/LC_MESSAGES/django.po b/tests/i18n/loading/en_AU/LC_MESSAGES/django.po
new file mode 100644
index 0000000000..ec21ac899d
--- /dev/null
+++ b/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"
diff --git a/tests/i18n/loading/en_AU/__init__.py b/tests/i18n/loading/en_AU/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading/en_AU/__init__.py
diff --git a/tests/i18n/loading/en_CA/LC_MESSAGES/django.mo b/tests/i18n/loading/en_CA/LC_MESSAGES/django.mo
new file mode 100644
index 0000000000..4d6da00f65
--- /dev/null
+++ b/tests/i18n/loading/en_CA/LC_MESSAGES/django.mo
diff --git a/tests/i18n/loading/en_CA/LC_MESSAGES/django.po b/tests/i18n/loading/en_CA/LC_MESSAGES/django.po
new file mode 100644
index 0000000000..06e52a4c55
--- /dev/null
+++ b/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"
diff --git a/tests/i18n/loading/en_CA/__init__.py b/tests/i18n/loading/en_CA/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading/en_CA/__init__.py
diff --git a/tests/i18n/loading/en_NZ/LC_MESSAGES/django.mo b/tests/i18n/loading/en_NZ/LC_MESSAGES/django.mo
new file mode 100644
index 0000000000..f71850a5b1
--- /dev/null
+++ b/tests/i18n/loading/en_NZ/LC_MESSAGES/django.mo
diff --git a/tests/i18n/loading/en_NZ/LC_MESSAGES/django.po b/tests/i18n/loading/en_NZ/LC_MESSAGES/django.po
new file mode 100644
index 0000000000..41b7499291
--- /dev/null
+++ b/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"
diff --git a/tests/i18n/loading/en_NZ/__init__.py b/tests/i18n/loading/en_NZ/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading/en_NZ/__init__.py
diff --git a/tests/i18n/loading_app/__init__.py b/tests/i18n/loading_app/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading_app/__init__.py
diff --git a/tests/i18n/loading_app/apps.py b/tests/i18n/loading_app/apps.py
new file mode 100644
index 0000000000..b4cdece232
--- /dev/null
+++ b/tests/i18n/loading_app/apps.py
@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class LoadingAppConfig(AppConfig):
+    name = 'loading_app'
diff --git a/tests/i18n/loading_app/locale/__init__.py b/tests/i18n/loading_app/locale/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading_app/locale/__init__.py
diff --git a/tests/i18n/loading_app/locale/en/LC_MESSAGES/django.mo b/tests/i18n/loading_app/locale/en/LC_MESSAGES/django.mo
new file mode 100644
index 0000000000..71cbdf3e9d
--- /dev/null
+++ b/tests/i18n/loading_app/locale/en/LC_MESSAGES/django.mo
diff --git a/tests/i18n/loading_app/locale/en/LC_MESSAGES/django.po b/tests/i18n/loading_app/locale/en/LC_MESSAGES/django.po
new file mode 100644
index 0000000000..e1422f19da
--- /dev/null
+++ b/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 ""
diff --git a/tests/i18n/loading_app/locale/en/__init__.py b/tests/i18n/loading_app/locale/en/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/tests/i18n/loading_app/locale/en/__init__.py
diff --git a/tests/i18n/tests.py b/tests/i18n/tests.py
index 8f07c14247..ccf4c242cf 100644
--- a/tests/i18n/tests.py
+++ b/tests/i18n/tests.py
@@ -384,6 +384,50 @@ 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', 'Canadian'),
+            ('en-nz', 'New Zealandian'),
+            ('en-au', 'Australian'),
+        ],
+        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 must be merged correctly.
+        """
+        tests = [
+            ('en', 'local country person'),
+            ('en_AU', 'aussie'),
+            ('en_NZ', 'kiwi'),
+            ('en_CA', 'canuck'),
+        ]
+        # All translations are loaded by the second pass.
+        for rnd in range(1, 3):
+            for language, nickname in tests:
+                with self.subTest(language=language, round=rnd):
+                    activate(language)
+                    self.assertEqual(gettext('local country person'), nickname)
+
+
 class TranslationThreadSafetyTests(SimpleTestCase):
 
     def setUp(self):