fix(network): keep blank values in Request.post_data_json for form bodies (#3248)

Author: MohammedAlkindi

playwright/_impl/_network.py

@@ -261,7 +261,7 @@ def post_data_json(self) -> Optional[Any]:
             return None
         content_type = self.headers.get("content-type")
         if content_type and "application/x-www-form-urlencoded" in content_type:
-            return dict(parse.parse_qsl(post_data))
+            return dict(parse.parse_qsl(post_data, keep_blank_values=True))
         try:
             return json.loads(post_data)
         except Exception:

tests/async/test_page_network_request.py

@@ -55,12 +55,12 @@ async def test_should_parse_the_data_if_content_type_is_application_x_www_form_u
             headers: {
             'content-type': 'application/x-www-form-urlencoded; charset=UTF-8',
             },
-            body: 'foo=bar&baz=123'
+            body: 'foo=bar&baz=123&empty='
         })"""
         )
     request = await request_info.value
     assert request
-    assert request.post_data_json == {"foo": "bar", "baz": "123"}
+    assert request.post_data_json == {"foo": "bar", "baz": "123", "empty": ""}
 
 
 async def test_existing_response_should_return_response_after_it_is_received(