fix: keep blank-valued query params significant in query_string_matcher

CHANGES

@@ -1,3 +1,11 @@
+0.26.3
+------
+
+* Fixed `query_string_matcher` (and the query matching auto-applied to a
+  registered URL's own query string) discarding blank-valued query params
+  (``b=``), which caused requests with an extra or missing blank param to
+  match incorrectly. See #804
+
 0.26.2
 ------
 

responses/matchers.py

@@ -259,8 +259,12 @@ def match(request: PreparedRequest) -> Tuple[bool, str]:
         data = parse_url(request.url or "")
         request_query = data.query
 
-        request_qsl = sorted(parse_qsl(request_query)) if request_query else {}
-        matcher_qsl = sorted(parse_qsl(query)) if query else {}
+        request_qsl = (
+            sorted(parse_qsl(request_query, keep_blank_values=True))
+            if request_query
+            else {}
+        )
+        matcher_qsl = sorted(parse_qsl(query, keep_blank_values=True)) if query else {}
 
         valid = not query if request_query is None else request_qsl == matcher_qsl
 

responses/tests/test_matchers.py

@@ -69,6 +69,40 @@ def run():
     assert_reset()
 
 
+def test_query_string_matcher_blank_values():
+    """A blank-valued query param (``foo=``) is significant: it must be present
+    to match, and an extra blank param must not be ignored."""
+
+    def run():
+        with responses.RequestsMock(assert_all_requests_are_fired=False) as rsps:
+            rsps.add(
+                responses.GET,
+                "http://example.com",
+                body=b"test",
+                match=[matchers.query_string_matcher("test=1&foo=")],
+            )
+            # Exact match, including the blank param, succeeds.
+            resp = requests.get("http://example.com?test=1&foo=")
+            assert_response(resp, "test")
+            # Omitting the required blank param must not match.
+            with pytest.raises(ConnectionError):
+                requests.get("http://example.com?test=1")
+
+        with responses.RequestsMock(assert_all_requests_are_fired=False) as rsps:
+            rsps.add(
+                responses.GET,
+                "http://example.com",
+                body=b"test",
+                match=[matchers.query_string_matcher("test=1")],
+            )
+            # An extra blank param must not be silently ignored.
+            with pytest.raises(ConnectionError):
+                requests.get("http://example.com?test=1&foo=")
+
+    run()
+    assert_reset()
+
+
 def test_request_matches_post_params():
     @responses.activate
     def run(deprecated):