Fixed #34515 -- Made LocaleMiddleware prefer language from paths when i18n patterns are used.

Regression in 94e7f471c4edef845a4fe5e3160132997b4cca81.

This reverts commit 94e7f471c4edef845a4fe5e3160132997b4cca81
(refs #34069) and
partly reverts commit 3b4728310a7a64f8fcc548163b0aa5f98a5c78f5.

Thanks Anthony Baillard for the report.

Co-Authored-By: Sarah Boyce <42296566+sarahboyce@users.noreply.github.com>

5 files changed, 20 insertions, 27 deletions

diff --git a/django/middleware/locale.py b/django/middleware/locale.py
index bc1d862574..71db230da2 100644
--- a/django/middleware/locale.py
+++ b/django/middleware/locale.py
@@ -16,37 +16,28 @@ class LocaleMiddleware(MiddlewareMixin):
 
     response_redirect_class = HttpResponseRedirect
 
-    def get_fallback_language(self, request):
-        """
-        Return the fallback language for the current request based on the
-        settings. If LANGUAGE_CODE is a variant not included in the supported
-        languages, get_fallback_language() will try to fallback to a supported
-        generic variant.
-
-        Can be overridden to have a fallback language depending on the request,
-        e.g. based on top level domain.
-        """
-        try:
-            return translation.get_supported_language_variant(settings.LANGUAGE_CODE)
-        except LookupError:
-            return settings.LANGUAGE_CODE
-
     def process_request(self, request):
         urlconf = getattr(request, "urlconf", settings.ROOT_URLCONF)
-        i18n_patterns_used, _ = is_language_prefix_patterns_used(urlconf)
+        (
+            i18n_patterns_used,
+            prefixed_default_language,
+        ) = is_language_prefix_patterns_used(urlconf)
         language = translation.get_language_from_request(
             request, check_path=i18n_patterns_used
         )
-        if not language:
-            language = self.get_fallback_language(request)
-
+        language_from_path = translation.get_language_from_path(request.path_info)
+        if (
+            not language_from_path
+            and i18n_patterns_used
+            and not prefixed_default_language
+        ):
+            language = settings.LANGUAGE_CODE
         translation.activate(language)
         request.LANGUAGE_CODE = translation.get_language()
 
     def process_response(self, request, response):
         language = translation.get_language()
         language_from_path = translation.get_language_from_path(request.path_info)
-        language_from_request = translation.get_language_from_request(request)
         urlconf = getattr(request, "urlconf", settings.ROOT_URLCONF)
         (
             i18n_patterns_used,
@@ -57,7 +48,7 @@ class LocaleMiddleware(MiddlewareMixin):
             response.status_code == 404
             and not language_from_path
             and i18n_patterns_used
-            and (prefixed_default_language or language_from_request)
+            and prefixed_default_language
         ):
             # Maybe the language code is missing in the URL? Try adding the
             # language prefix and redirecting to that URL.
diff --git a/django/urls/resolvers.py b/django/urls/resolvers.py
index 658a6a6f97..b021673772 100644
--- a/django/urls/resolvers.py
+++ b/django/urls/resolvers.py
@@ -23,7 +23,7 @@ from django.utils.datastructures import MultiValueDict
 from django.utils.functional import cached_property
 from django.utils.http import RFC3986_SUBDELIMS, escape_leading_slashes
 from django.utils.regex_helper import _lazy_re_compile, normalize
-from django.utils.translation import get_language, get_supported_language_variant
+from django.utils.translation import get_language
 
 from .converters import get_converter
 from .exceptions import NoReverseMatch, Resolver404
@@ -351,8 +351,7 @@ class LocalePrefixPattern:
     @property
     def language_prefix(self):
         language_code = get_language() or settings.LANGUAGE_CODE
-        default_language = get_supported_language_variant(settings.LANGUAGE_CODE)
-        if language_code == default_language and not self.prefix_default_language:
+        if language_code == settings.LANGUAGE_CODE and not self.prefix_default_language:
             return ""
         else:
             return "%s/" % language_code
diff --git a/django/utils/translation/__init__.py b/django/utils/translation/__init__.py
index 69820a2fc4..0b3f78e486 100644
--- a/django/utils/translation/__init__.py
+++ b/django/utils/translation/__init__.py
@@ -17,7 +17,6 @@ __all__ = [
     "get_language_from_request",
     "get_language_info",
     "get_language_bidi",
-    "get_supported_language_variant",
     "check_for_language",
     "to_language",
     "to_locale",
diff --git a/django/utils/translation/trans_null.py b/django/utils/translation/trans_null.py
index 595a705e2b..c8bfb1256e 100644
--- a/django/utils/translation/trans_null.py
+++ b/django/utils/translation/trans_null.py
@@ -53,7 +53,7 @@ def check_for_language(x):
 
 
 def get_language_from_request(request, check_path=False):
-    return None
+    return settings.LANGUAGE_CODE
 
 
 def get_language_from_path(request):
diff --git a/django/utils/translation/trans_real.py b/django/utils/translation/trans_real.py
index 46a94b99ff..872c80b00f 100644
--- a/django/utils/translation/trans_real.py
+++ b/django/utils/translation/trans_real.py
@@ -583,7 +583,11 @@ def get_language_from_request(request, check_path=False):
             return get_supported_language_variant(accept_lang)
         except LookupError:
             continue
-    return None
+
+    try:
+        return get_supported_language_variant(settings.LANGUAGE_CODE)
+    except LookupError:
+        return settings.LANGUAGE_CODE
 
 
 @functools.lru_cache(maxsize=1000)