[5.2.x] Fixed #36446 -- Restored "q" in internal MediaType.params property.

The "q" key was removed while addressing ticket #36411. Despite
`MediaType.params` is undocumented and considered internal, it was used
in third-party projects (Zulip reported breakage), so this work restored
the `q` key in `params`.

Thanks Anders Kaseorg for the report.

Regression in c075508b4de8edf9db553b409f8a8ed2f26ecead.

Backport of cf5f36bf903a2854f5e395149cee707115b83744 from main.

3 files changed, 69 insertions, 10 deletions

diff --git a/django/http/request.py b/django/http/request.py
index 6438f26268..c26a4954d1 100644
--- a/django/http/request.py
+++ b/django/http/request.py
@@ -694,13 +694,13 @@ class QueryDict(MultiValueDict):
 
 class MediaType:
     def __init__(self, media_type_raw_line):
-        full_type, self._params = parse_header_parameters(
+        full_type, self.params = parse_header_parameters(
             media_type_raw_line if media_type_raw_line else ""
         )
         self.main_type, _, self.sub_type = full_type.partition("/")
 
     def __str__(self):
-        params_str = "".join("; %s=%s" % (k, v) for k, v in self._params.items())
+        params_str = "".join("; %s=%s" % (k, v) for k, v in self.params.items())
         return "%s%s%s" % (
             self.main_type,
             ("/%s" % self.sub_type) if self.sub_type else "",
@@ -711,8 +711,8 @@ class MediaType:
         return "<%s: %s>" % (self.__class__.__qualname__, self)
 
     @cached_property
-    def params(self):
-        params = self._params.copy()
+    def range_params(self):
+        params = self.params.copy()
         params.pop("q", None)
         return params
 
@@ -735,20 +735,19 @@ class MediaType:
             if this_type != other_type and this_type != "*" and other_type != "*":
                 return False
 
-        if bool(self.params) == bool(other.params):
+        if bool(self.range_params) == bool(other.range_params):
             # If both have params or neither have params, they must be identical.
-            result = self.params == other.params
+            result = self.range_params == other.range_params
         else:
             # If self has params and other does not, it's a match.
             # If other has params and self does not, don't match.
-            result = bool(self.params or not other.params)
-
+            result = bool(self.range_params or not other.range_params)
         return result
 
     @cached_property
     def quality(self):
         try:
-            quality = float(self._params.get("q", 1))
+            quality = float(self.params.get("q", 1))
         except ValueError:
             # Discard invalid values.
             return 1
@@ -768,7 +767,7 @@ class MediaType:
             return 0
         elif self.sub_type == "*":
             return 1
-        elif not self.params:
+        elif not self.range_params:
             return 2
         return 3
 
diff --git a/docs/releases/5.2.3.txt b/docs/releases/5.2.3.txt
index 927ec16d34..70aa5aedb0 100644
--- a/docs/releases/5.2.3.txt
+++ b/docs/releases/5.2.3.txt
@@ -17,3 +17,6 @@ Bugfixes
 * Fixed a regression in Django 5.2 that caused :meth:`.QuerySet.bulk_update` to
   incorrectly convert ``None`` to JSON ``null`` instead of SQL ``NULL`` for
   ``JSONField`` (:ticket:`36419`).
+
+* Fixed a regression in Django 5.2.2 where the ``q`` parameter was removed from
+  the internal ``django.http.MediaType.params`` property (:ticket:`36446`).
diff --git a/tests/requests_tests/test_accept_header.py b/tests/requests_tests/test_accept_header.py
index 37826278e2..608af58b62 100644
--- a/tests/requests_tests/test_accept_header.py
+++ b/tests/requests_tests/test_accept_header.py
@@ -15,6 +15,10 @@ class MediaTypeTests(TestCase):
     def test_str(self):
         self.assertEqual(str(MediaType("*/*; q=0.8")), "*/*; q=0.8")
         self.assertEqual(str(MediaType("application/xml")), "application/xml")
+        self.assertEqual(
+            str(MediaType("application/xml;type=madeup;q=42")),
+            "application/xml; type=madeup; q=42",
+        )
 
     def test_repr(self):
         self.assertEqual(repr(MediaType("*/*; q=0.8")), "<MediaType: */*; q=0.8>")
@@ -34,6 +38,7 @@ class MediaTypeTests(TestCase):
             (" application/xml ", "application/xml"),
             ("application/xml", " application/xml "),
             ("text/vcard; version=4.0", "text/vcard; version=4.0"),
+            ("text/vcard; version=4.0; q=0.7", "text/vcard; version=4.0"),
             ("text/vcard; version=4.0", "text/vcard"),
         ]
         for accepted_type, mime_type in tests:
@@ -58,12 +63,64 @@ class MediaTypeTests(TestCase):
             # All main and sub types are defined, but there is no match.
             ("application/xml", "application/html"),
             ("text/vcard; version=4.0", "text/vcard; version=3.0"),
+            ("text/vcard; q=0.7", "text/vcard; version=3.0"),
             ("text/vcard", "text/vcard; version=3.0"),
         ]
         for accepted_type, mime_type in tests:
             with self.subTest(accepted_type, mime_type=mime_type):
                 self.assertIs(MediaType(accepted_type).match(mime_type), False)
 
+    def test_params(self):
+        tests = [
+            ("text/plain", {}, {}),
+            ("text/plain;q=0.7", {"q": "0.7"}, {}),
+            ("text/plain;q=1.5", {"q": "1.5"}, {}),
+            ("text/plain;q=xyz", {"q": "xyz"}, {}),
+            ("text/plain;q=0.1234", {"q": "0.1234"}, {}),
+            ("text/plain;version=2", {"version": "2"}, {"version": "2"}),
+            (
+                "text/plain;version=2;q=0.8",
+                {"version": "2", "q": "0.8"},
+                {"version": "2"},
+            ),
+            (
+                "text/plain;q=0.8;version=2",
+                {"q": "0.8", "version": "2"},
+                {"version": "2"},
+            ),
+            (
+                "text/plain; charset=UTF-8; q=0.3",
+                {"charset": "UTF-8", "q": "0.3"},
+                {"charset": "UTF-8"},
+            ),
+            (
+                "text/plain ; q = 0.5 ; version = 3.0",
+                {"q": "0.5", "version": "3.0"},
+                {"version": "3.0"},
+            ),
+            ("text/plain; format=flowed", {"format": "flowed"}, {"format": "flowed"}),
+            (
+                "text/plain; format=flowed; q=0.4",
+                {"format": "flowed", "q": "0.4"},
+                {"format": "flowed"},
+            ),
+            ("text/*;q=0.2", {"q": "0.2"}, {}),
+            ("*/json;q=0.9", {"q": "0.9"}, {}),
+            ("application/json;q=0.9999", {"q": "0.9999"}, {}),
+            ("text/html;q=0.0001", {"q": "0.0001"}, {}),
+            ("text/html;q=0", {"q": "0"}, {}),
+            ("text/html;q=0.", {"q": "0."}, {}),
+            ("text/html;q=.8", {"q": ".8"}, {}),
+            ("text/html;q= 0.9", {"q": "0.9"}, {}),
+            ('text/html ; q = "0.6"', {"q": "0.6"}, {}),
+        ]
+        for accepted_type, params, range_params in tests:
+            media_type = MediaType(accepted_type)
+            with self.subTest(accepted_type, attr="params"):
+                self.assertEqual(media_type.params, params)
+            with self.subTest(accepted_type, attr="range_params"):
+                self.assertEqual(media_type.range_params, range_params)
+
     def test_quality(self):
         tests = [
             ("*/*; q=0.8", 0.8),