Add helpers for typing proxies

pyproject.toml

@@ -18,6 +18,7 @@ include = ["docs", "examples", "tests"]
 
 [tool.poetry.dependencies]
 python = "^3.8.0"
+typing-extensions = { version = "^4.0.0", python = "<3.10" }
 
 [tool.poetry.group.black.dependencies]
 black = "^23.3.0"

src/pykka/typing.py

@@ -0,0 +1,92 @@
+"""The :mod:`pykka.typing` module contains helpers to improve type hints.
+
+Example usage::
+
+    from typing import cast
+
+    from pykka import ActorProxy, ThreadingActor
+    from pykka.typing import ActorMemberMixin, proxy_field, proxy_method
+
+    class CircleActor(ThreadingActor):
+        pi = 3.14
+
+        def area(self, radius: float) -> float:
+            return self.pi * radius**2
+
+    class CircleProxy(ActorMemberMixin, ActorProxy[CircleActor]):
+        pi = proxy_field(CircleActor.pi)
+        area = proxy_method(CircleActor.area)
+
+    proxy = cast(CircleProxy, CircleActor.start().proxy())
+
+    reveal_type(proxy.stop)
+    # Revealed type is 'Callable[[], pykka.Future[None]]'
+
+    reveal_type(proxy.pi)
+    # Revealed type is 'pykka.Future[float]'
+
+    reveal_type(proxy.area))
+    # Revealed type is 'Callable[[float], pykka.Future[float]]'
+"""
+
+from __future__ import annotations
+
+import sys
+from typing import TYPE_CHECKING, Any, Callable, Generic, Protocol, TypeVar
+
+from pykka import Actor
+
+if TYPE_CHECKING:
+    from pykka import Future
+
+if sys.version_info >= (3, 10):
+    from typing import (
+        Concatenate,
+        ParamSpec,
+    )
+else:
+    from typing_extensions import (
+        Concatenate,
+        ParamSpec,
+    )
+
+__all__ = [
+    "ActorMemberMixin",
+    "proxy_field",
+    "proxy_method",
+]
+
+
+T = TypeVar("T")
+P = ParamSpec("P")
+R = TypeVar("R", covariant=True)
+
+
+class Method(Protocol, Generic[P, R]):
+    def __get__(self, instance: Any, owner: type | None = None) -> Callable[P, R]:
+        ...
+
+    def __call__(self, obj: Any, *args: P.args, **kwargs: P.kwargs) -> R:
+        ...
+
+
+def proxy_field(field: T) -> Future[T]:
+    """Type a field on an actor proxy."""
+    return field  # type: ignore[return-value]
+
+
+def proxy_method(
+    field: Callable[Concatenate[Any, P], T],
+) -> Method[P, Future[T]]:
+    """Type a method on an actor proxy."""
+    return field  # type: ignore[return-value]
+
+
+class ActorMemberMixin:
+    """Mixin class for typing actor members accessible through a proxy."""
+
+    stop = proxy_method(Actor.stop)
+    on_start = proxy_method(Actor.on_start)
+    on_stop = proxy_method(Actor.on_stop)
+    on_failure = proxy_method(Actor.on_failure)
+    on_receive = proxy_method(Actor.on_receive)

tests/proxy/test_typed_proxy.py

@@ -0,0 +1,69 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Iterator, cast
+
+import pytest
+
+import pykka
+from pykka import Actor, ActorProxy
+from pykka.typing import ActorMemberMixin, proxy_field, proxy_method
+
+if TYPE_CHECKING:
+    from tests.types import Runtime
+
+
+@dataclass
+class Constants:
+    pi: float
+
+
+class CircleActor(Actor):
+    constants = pykka.traversable(Constants(pi=3.14))
+    text: str = "The fox crossed the road."
+
+    def area(self, radius: float) -> float:
+        return self.constants.pi * radius**2
+
+
+class ConstantsProxy:
+    pi = proxy_field(CircleActor.constants.pi)
+
+
+class FooProxy(ActorMemberMixin, ActorProxy[CircleActor]):
+    numbers: ConstantsProxy
+    text = proxy_field(CircleActor.text)
+    area = proxy_method(CircleActor.area)
+
+
+@pytest.fixture(scope="module")
+def actor_class(runtime: Runtime) -> type[CircleActor]:
+    class FooActorImpl(CircleActor, runtime.actor_class):  # type: ignore[name-defined]  # noqa: E501
+        pass
+
+    return FooActorImpl
+
+
+@pytest.fixture()
+def proxy(
+    actor_class: type[CircleActor],
+) -> Iterator[FooProxy]:
+    proxy = cast(FooProxy, actor_class.start().proxy())
+    yield proxy
+    proxy.stop()
+
+
+def test_proxy_field(proxy: FooProxy) -> None:
+    assert proxy.text.get() == "The fox crossed the road."
+
+
+def test_proxy_traversable_object_field(proxy: FooProxy) -> None:
+    assert proxy.constants.pi.get() == 3.14
+
+
+def test_proxy_method(proxy: FooProxy) -> None:
+    assert proxy.area(2.0).get() == 12.56
+
+
+def test_proxy_to_actor_methods(proxy: FooProxy) -> None:
+    assert proxy.stop().get() is None