Fixed #36488 -- Fixed merging of query strings in RedirectView.

Co-authored-by: Ethan Jucovy <ethan.jucovy@gmail.com>
Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

2 files changed, 30 insertions, 1 deletions

diff --git a/django/views/generic/base.py b/django/views/generic/base.py
index 8412288be1..485b74d377 100644
--- a/django/views/generic/base.py
+++ b/django/views/generic/base.py
@@ -1,4 +1,5 @@
 import logging
+from urllib.parse import urlparse
 
 from asgiref.sync import iscoroutinefunction, markcoroutinefunction
 
@@ -252,7 +253,10 @@ class RedirectView(View):
 
         args = self.request.META.get("QUERY_STRING", "")
         if args and self.query_string:
-            url = "%s?%s" % (url, args)
+            if urlparse(url).query:
+                url = f"{url}&{args}"
+            else:
+                url = f"{url}?{args}"
         return url
 
     def get(self, request, *args, **kwargs):
diff --git a/tests/generic_views/test_base.py b/tests/generic_views/test_base.py
index cc5dcf4e39..9d6cef8a46 100644
--- a/tests/generic_views/test_base.py
+++ b/tests/generic_views/test_base.py
@@ -587,6 +587,31 @@ class RedirectViewTest(LoggingAssertionMixin, SimpleTestCase):
                     handler, f"Gone: {escaped}", logging.WARNING, 410, request
                 )
 
+    def test_redirect_with_querry_string_in_destination(self):
+        response = RedirectView.as_view(url="/bar/?pork=spam", query_string=True)(
+            self.rf.get("/foo")
+        )
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response.headers["Location"], "/bar/?pork=spam")
+
+    def test_redirect_with_query_string_in_destination_and_request(self):
+        response = RedirectView.as_view(url="/bar/?pork=spam", query_string=True)(
+            self.rf.get("/foo/?utm_source=social")
+        )
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(
+            response.headers["Location"], "/bar/?pork=spam&utm_source=social"
+        )
+
+    def test_redirect_with_same_query_string_param_will_append_not_replace(self):
+        response = RedirectView.as_view(url="/bar/?pork=spam", query_string=True)(
+            self.rf.get("/foo/?utm_source=social&pork=ham")
+        )
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(
+            response.headers["Location"], "/bar/?pork=spam&utm_source=social&pork=ham"
+        )
+
 
 class GetContextDataTest(SimpleTestCase):
     def test_get_context_data_super(self):