[3.2.x] Fixed #32345 -- Fixed preserving encoded query strings in set_language() view.

Thanks Johannes Maron for the review.

Backport of 6822aa5c6c from master

django/urls/base.py

@@ -1,4 +1,4 @@
-from urllib.parse import urlsplit, urlunsplit
+from urllib.parse import unquote, urlsplit, urlunsplit
 
 from asgiref.local import Local
 
@@ -163,7 +163,8 @@ def translate_url(url, lang_code):
     """
     parsed = urlsplit(url)
     try:
-        match = resolve(parsed.path)
+        # URL may be encoded.
+        match = resolve(unquote(parsed.path))
     except Resolver404:
         pass
     else:

django/views/i18n.py

@@ -2,7 +2,6 @@ import itertools
 import json
 import os
 import re
-from urllib.parse import unquote
 
 from django.apps import apps
 from django.conf import settings
@@ -41,8 +40,6 @@ def set_language(request):
         )
     ):
         next_url = request.META.get('HTTP_REFERER')
-        # HTTP_REFERER may be encoded.
-        next_url = next_url and unquote(next_url)
         if not url_has_allowed_host_and_scheme(
             url=next_url,
             allowed_hosts={request.get_host()},

tests/view_tests/tests/test_i18n.py

@@ -199,12 +199,14 @@ class SetLanguageTests(TestCase):
 
     def test_setlang_decodes_http_referer_url(self):
         """
-        The set_language view decodes the HTTP_REFERER URL.
+        The set_language view decodes the HTTP_REFERER URL and preserves an
+        encoded query string.
         """
         # The URL & view must exist for this to work as a regression test.
         self.assertEqual(reverse('with_parameter', kwargs={'parameter': 'x'}), '/test-setlang/x/')
         lang_code = self._get_inactive_language_code()
-        encoded_url = '/test-setlang/%C3%A4/'  # (%C3%A4 decodes to ä)
+        # %C3%A4 decodes to ä, %26 to &.
+        encoded_url = '/test-setlang/%C3%A4/?foo=bar&baz=alpha%26omega'
         response = self.client.post('/i18n/setlang/', {'language': lang_code}, HTTP_REFERER=encoded_url)
         self.assertRedirects(response, encoded_url, fetch_redirect_response=False)
         self.assertEqual(self.client.cookies[settings.LANGUAGE_COOKIE_NAME].value, lang_code)