Handle get_supported_language_variant returning a language variant not in LANGUAGES (#6547)

* Handle get_supported_language_variant returning a language variant not in LANGUAGES

Fixes #6539

* Handle LANGUAGE_CODE that isn't in LANGUAGES

* Release note for #6547

CHANGELOG.txt

@@ -12,6 +12,7 @@ Changelog
 
  * Fix: Improve performance of permission check on translations for edit page (Karl Hobley)
  * Fix: Gracefully handle missing Locale records on `Locale.get_active` and `.localized` (Matt Westcott)
+ * Fix: Handle `get_supported_language_variant` returning a language variant not in `LANGUAGES` (Matt Westcott)
 
 
 2.11.1 (06.11.2020)

docs/releases/2.11.2.rst

@@ -15,3 +15,4 @@ Bug fixes
 
  * Improve performance of permission check on translations for edit page (Karl Hobley)
  * Gracefully handle missing Locale records on ``Locale.get_active`` and ``.localized`` (Matt Westcott)
+ * Handle ``get_supported_language_variant`` returning a language variant not in ``LANGUAGES`` (Matt Westcott)

wagtail/core/tests/test_utils.py

@@ -2,6 +2,7 @@
 from django.core.exceptions import ImproperlyConfigured
 from django.test import TestCase, override_settings
 from django.utils.text import slugify
+from django.utils.translation import _trans
 
 from wagtail.core.models import Page
 from wagtail.core.utils import (
@@ -259,3 +260,36 @@ class TestGetSupportedContentLanguageVariant(TestCase):
             g('xyz')
         with self.assertRaises(LookupError):
             g('xy-zz')
+
+
+@override_settings(
+    USE_I18N=False,
+    WAGTAIL_I18N_ENABLED=False,
+    WAGTAIL_CONTENT_LANGUAGES=None,
+    LANGUAGE_CODE='en-us',
+)
+class TestGetSupportedContentLanguageVariantWithI18nFalse(TestCase):
+    def setUp(self):
+        # Need to forcibly clear the django.utils.translation._trans object when overriding
+        # USE_I18N:
+        # https://github.com/django/django/blob/3.1/django/utils/translation/__init__.py#L46-L48
+        _trans.__dict__.clear()
+
+    def tearDown(self):
+        _trans.__dict__.clear()
+
+    def test_lookup_language_with_i18n_false(self):
+        # Make sure we can handle the 'null' USE_I18N=False implementation of
+        # get_supported_language_variant returning 'en-us' rather than 'en',
+        # despite 'en-us' not being in LANGUAGES.
+        # https://github.com/wagtail/wagtail/issues/6539
+
+        self.assertEqual(get_supported_content_language_variant('en-us'), 'en')
+
+    @override_settings(LANGUAGE_CODE='zz')
+    def test_language_code_not_in_languages(self):
+        # Ensure we can handle a LANGUAGE_CODE setting that isn't defined in LANGUAGES -
+        # in this case get_content_languages has to cope with not being able to retrieve
+        # a display name for the language
+        self.assertEqual(get_supported_content_language_variant('zz'), 'zz')
+        self.assertEqual(get_supported_content_language_variant('zz-gb'), 'zz')

wagtail/core/utils.py

@@ -220,8 +220,23 @@ def get_content_languages():
     if content_languages is None:
         # Default to a single language based on LANGUAGE_CODE
         default_language_code = get_supported_language_variant(settings.LANGUAGE_CODE)
+        try:
+            language_name = languages[default_language_code]
+        except KeyError:
+            # get_supported_language_variant on the 'null' translation backend (used for
+            # USE_I18N=False) returns settings.LANGUAGE_CODE unchanged without accounting for
+            # language variants (en-us versus en), so retry with the generic version.
+            default_language_code = default_language_code.split("-")[0]
+            try:
+                language_name = languages[default_language_code]
+            except KeyError:
+                # Can't extract a display name, so fall back on displaying LANGUAGE_CODE instead
+                language_name = settings.LANGUAGE_CODE
+                # Also need to tweak the languages dict to get around the check below
+                languages[default_language_code] = settings.LANGUAGE_CODE
+
         content_languages = [
-            (default_language_code, languages[default_language_code]),
+            (default_language_code, language_name),
         ]
 
     # Check that each content language is in LANGUAGES