Fix requires_feature decorator breaking named arguments (#21)

Author: jpelgrom

letpot/deviceclient.py

@@ -10,7 +10,7 @@
 from datetime import time
 from functools import wraps
 from hashlib import md5, sha256
-from typing import Any, Callable, Concatenate
+from typing import Any, Callable, ParamSpec, TypeVar, cast
 
 import aiomqtt
 
@@ -32,32 +32,26 @@
 
 _LOGGER = logging.getLogger(__name__)
 
+T = TypeVar("T", bound="LetPotDeviceClient")
+_R = TypeVar("_R")
+P = ParamSpec("P")
 
-def _create_ssl_context() -> ssl.SSLContext:
-    """Create a SSL context for the MQTT connection, avoids a blocking call later."""
-    context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
-    context.load_default_certs()
-    return context
 
-
-_SSL_CONTEXT = _create_ssl_context()
-
-
-def requires_feature[T: "LetPotDeviceClient", _R, **P](
+def requires_feature(
     *required_feature: DeviceFeature,
 ) -> Callable[
-    [Callable[Concatenate[T, str, P], Coroutine[Any, Any, _R]]],
-    Callable[Concatenate[T, str, P], Coroutine[Any, Any, _R]],
+    [Callable[P, Coroutine[Any, Any, _R]]],
+    Callable[P, Coroutine[Any, Any, _R]],
 ]:
     """Decorate the function to require device type support for a specific feature (inferred from serial)."""
 
     def decorator(
-        func: Callable[Concatenate[T, str, P], Coroutine[Any, Any, _R]],
-    ) -> Callable[Concatenate[T, str, P], Coroutine[Any, Any, _R]]:
+        func: Callable[P, Coroutine[Any, Any, _R]],
+    ) -> Callable[P, Coroutine[Any, Any, _R]]:
         @wraps(func)
-        async def wrapper(
-            self: T, serial: str, *args: P.args, **kwargs: P.kwargs
-        ) -> _R:
+        async def wrapper(*args: P.args, **kwargs: P.kwargs) -> _R:
+            self = cast(LetPotDeviceClient, args[0])
+            serial = cast(str, args[1])
             exception_message = f"Device missing required feature: {required_feature}"
             try:
                 supported_features = self._converter(serial).supported_features()
@@ -67,13 +61,23 @@ async def wrapper(
                     raise LetPotFeatureException(exception_message)
             except LetPotException:
                 raise LetPotFeatureException(exception_message)
-            return await func(self, serial, *args, **kwargs)
+            return await func(*args, **kwargs)
 
         return wrapper
 
     return decorator
 
 
+def _create_ssl_context() -> ssl.SSLContext:
+    """Create a SSL context for the MQTT connection, avoids a blocking call later."""
+    context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+    context.load_default_certs()
+    return context
+
+
+_SSL_CONTEXT = _create_ssl_context()
+
+
 class LetPotDeviceClient:
     """Client for connecting to LetPot device."""