Fix handler wrapping for keyword-only parameters

playwright/_impl/_impl_to_api_mapping.py

@@ -119,7 +119,23 @@ def to_impl(
 
     def wrap_handler(self, handler: Callable[..., Any]) -> Callable[..., None]:
         def wrapper_func(*args: Any) -> Any:
-            arg_count = len(inspect.signature(handler).parameters)
+            parameters = inspect.signature(handler).parameters
+            has_varargs = any(
+                parameter.kind == inspect.Parameter.VAR_POSITIONAL
+                for parameter in parameters.values()
+            )
+            arg_count = (
+                len(args)
+                if has_varargs
+                else sum(
+                    parameter.kind
+                    in (
+                        inspect.Parameter.POSITIONAL_ONLY,
+                        inspect.Parameter.POSITIONAL_OR_KEYWORD,
+                    )
+                    for parameter in parameters.values()
+                )
+            )
             return handler(
                 *list(map(lambda a: self.from_maybe_impl(a), args))[:arg_count]
             )

tests/common/test_impl_to_api_mapping.py

@@ -0,0 +1,29 @@
+# Copyright (c) Microsoft Corporation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import List, Optional
+
+from playwright._impl._impl_to_api_mapping import ImplToApiMapping
+
+
+def test_wrap_handler_ignores_keyword_only_parameters() -> None:
+    calls: List[Optional[int]] = []
+
+    class Input:
+        def blur(self, *, timeout: Optional[int] = None) -> None:
+            calls.append(timeout)
+
+    ImplToApiMapping().wrap_handler(Input().blur)("locator")
+
+    assert calls == [None]