[5.2.x] Fixed #36447 -- Selected preferred media type based on quality.

When matching which entry in the `Accept` header should be used for
a given media type, the specificity matters. However once those are
resolved, only the quality matters when selecting preference.

Regression in c075508b4de8edf9db553b409f8a8ed2f26ecead.

Thank you to Anders Kaseorg for the report.

Backport of 12c1557060fc94fe5e1fbddc4578a4e29d38f77c from main.

1 files changed, 75 insertions, 3 deletions

diff --git a/tests/requests_tests/test_accept_header.py b/tests/requests_tests/test_accept_header.py
index 608af58b62..f6febc937a 100644
--- a/tests/requests_tests/test_accept_header.py
+++ b/tests/requests_tests/test_accept_header.py
@@ -173,6 +173,19 @@ class AcceptHeaderTests(TestCase):
             [
                 "text/html",
                 "application/xhtml+xml",
+                "text/*",
+                "application/xml; q=0.9",
+                "*/*; q=0.8",
+            ],
+        )
+        self.assertEqual(
+            [
+                str(accepted_type)
+                for accepted_type in request.accepted_types_by_precedence
+            ],
+            [
+                "text/html",
+                "application/xhtml+xml",
                 "application/xml; q=0.9",
                 "text/*",
                 "*/*; q=0.8",
@@ -196,7 +209,10 @@ class AcceptHeaderTests(TestCase):
             "text/*, text/plain, text/plain;format=flowed, */*"
         )
         self.assertEqual(
-            [str(accepted_type) for accepted_type in request.accepted_types],
+            [
+                str(accepted_type)
+                for accepted_type in request.accepted_types_by_precedence
+            ],
             [
                 "text/plain; format=flowed",
                 "text/plain",
@@ -261,6 +277,16 @@ class AcceptHeaderTests(TestCase):
                 "text/*; q=0.8",
             ],
         )
+        self.assertEqual(
+            [
+                str(accepted_type)
+                for accepted_type in request.accepted_types_by_precedence
+            ],
+            [
+                "text/html; q=0.8",
+                "text/*; q=0.8",
+            ],
+        )
 
     def test_no_matching_accepted_type(self):
         request = HttpRequest()
@@ -289,7 +315,7 @@ class AcceptHeaderTests(TestCase):
         ]:
             self.assertEqual(request.get_preferred_type(media_types), expected)
 
-    def test_quality(self):
+    def test_quality_for_media_type_rfc7231(self):
         """
         Taken from https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2.
         """
@@ -314,7 +340,36 @@ class AcceptHeaderTests(TestCase):
 
         for media_types, expected in [
             (["text/html", "text/html; level=1"], "text/html; level=1"),
-            (["text/html; level=2", "text/html; level=3"], "text/html; level=2"),
+            (["text/html; level=2", "text/html; level=3"], "text/html; level=3"),
+        ]:
+            self.assertEqual(request.get_preferred_type(media_types), expected)
+
+    def test_quality_for_media_type_rfc9110(self):
+        """
+        Taken from https://www.rfc-editor.org/rfc/rfc9110.html#section-12.5.1-18.
+        """
+        request = HttpRequest()
+        request.META["HTTP_ACCEPT"] = (
+            "text/*;q=0.3, text/plain;q=0.7, text/plain;format=flowed, "
+            "text/plain;format=fixed;q=0.4, */*;q=0.5"
+        )
+
+        for media_type, quality in [
+            ("text/plain;format=flowed", 1),
+            ("text/plain", 0.7),
+            ("text/html", 0.3),
+            ("image/jpeg", 0.5),
+            ("text/plain;format=fixed", 0.4),
+            ("text/html;level=3", 0.3),  # https://www.rfc-editor.org/errata/eid7138
+        ]:
+            with self.subTest(media_type):
+                accepted_media_type = request.accepted_type(media_type)
+                self.assertIsNotNone(accepted_media_type)
+                self.assertEqual(accepted_media_type.quality, quality)
+
+        for media_types, expected in [
+            (["text/plain", "text/plain; format=flowed"], "text/plain; format=flowed"),
+            (["text/html", "image/jpeg"], "image/jpeg"),
         ]:
             self.assertEqual(request.get_preferred_type(media_types), expected)
 
@@ -334,3 +389,20 @@ class AcceptHeaderTests(TestCase):
         self.assertEqual(
             request.get_preferred_type(["text/html", "text/plain"]), "text/html"
         )
+
+    def test_quality_over_specificity(self):
+        """
+        For media types with the same quality, prefer the more specific type.
+        """
+        request = HttpRequest()
+        request.META["HTTP_ACCEPT"] = "text/*,image/jpeg"
+
+        self.assertEqual(request.accepted_type("text/plain").quality, 1)
+        self.assertEqual(request.accepted_type("text/plain").specificity, 1)
+
+        self.assertEqual(request.accepted_type("image/jpeg").quality, 1)
+        self.assertEqual(request.accepted_type("image/jpeg").specificity, 2)
+
+        self.assertEqual(
+            request.get_preferred_type(["text/plain", "image/jpeg"]), "image/jpeg"
+        )