Preserve blank parameters in fragment identifier matching

CHANGES

@@ -1,6 +1,8 @@
 Unreleased
 ----------
 
+* Fixed ``fragment_identifier_matcher`` ignoring blank-valued fragment
+  parameters, which allowed missing or different parameters to match.
 * Added Python 3.14 support (classifiers, tox envlist, and CI test matrix). See #810
 * Match response ``Content-Type`` header names case-insensitively so lowercase
   headers do not produce duplicate content types or incorrect response decoding.

responses/matchers.py

@@ -180,8 +180,10 @@ def match(request: PreparedRequest) -> Tuple[bool, str]:
         if identifier:
             if "=" in identifier:
                 # Query-string-style fragment: compare order-insensitively.
-                url_fragment_qsl = sorted(parse_qsl(url_fragment))  # type: ignore[type-var]
-                identifier_qsl = sorted(parse_qsl(identifier))
+                url_fragment_qsl = sorted(
+                    parse_qsl(url_fragment, keep_blank_values=True)  # type: ignore[type-var]
+                )
+                identifier_qsl = sorted(parse_qsl(identifier, keep_blank_values=True))
                 valid = identifier_qsl == url_fragment_qsl
             else:
                 # Opaque fragment (e.g. "/users/5"): parse_qsl() yields no

responses/tests/test_matchers.py

@@ -1033,6 +1033,44 @@ def run():
     assert_reset()
 
 
+@pytest.mark.parametrize(
+    "expected, actual, matches",
+    [
+        ("flag=", "flag=", True),
+        ("flag=", "other=", False),
+        ("flag=", "", False),
+        ("flag=&value=1", "value=1&flag=", True),
+        ("flag=&value=1", "value=1", False),
+        ("flag=&value=1", "flag=present&value=1", False),
+        ("flag=&flag=1", "flag=1&flag=", True),
+        ("flag=&flag=1", "flag=1", False),
+    ],
+)
+def test_fragment_identifier_matcher_blank_values(
+    expected: str, actual: str, matches: bool
+) -> None:
+    request = requests.Request("GET", f"http://example.com/#{actual}").prepare()
+    valid, reason = matchers.fragment_identifier_matcher(expected)(request)
+    assert valid is matches
+    if matches:
+        assert reason == ""
+    else:
+        assert "URL fragment identifier is different" in reason
+
+
+@responses.activate
+def test_fragment_identifier_matcher_blank_values_in_requests() -> None:
+    responses.add(
+        responses.GET,
+        "http://example.com/",
+        match=[matchers.fragment_identifier_matcher("flag=&value=1")],
+        body=b"test",
+    )
+    with pytest.raises(ConnectionError, match="URL fragment identifier is different"):
+        requests.get("http://example.com/#value=1")
+    assert_response(requests.get("http://example.com/#value=1&flag="), "test")
+
+
 def test_fragment_identifier_matcher_opaque():
     """Opaque (non key=value) fragments must compare verbatim.