Fix performance regression with SignalType (#117920)

.pre-commit-config.yaml

@@ -61,15 +61,15 @@ repos:
         name: mypy
         entry: script/run-in-env.sh mypy
         language: script
-        types: [python]
+        types_or: [python, pyi]
         require_serial: true
         files: ^(homeassistant|pylint)/.+\.(py|pyi)$
       - id: pylint
         name: pylint
         entry: script/run-in-env.sh pylint -j 0 --ignore-missing-annotations=y
         language: script
-        types: [python]
-        files: ^homeassistant/.+\.py$
+        types_or: [python, pyi]
+        files: ^homeassistant/.+\.(py|pyi)$
       - id: gen_requirements_all
         name: gen_requirements_all
         entry: script/run-in-env.sh python3 -m script.gen_requirements_all

homeassistant/util/signal_type.py

@@ -2,40 +2,20 @@
 
 from __future__ import annotations
 
-from dataclasses import dataclass
-from typing import Any
 
-
-@dataclass(frozen=True)
-class _SignalTypeBase[*_Ts]:
+class _SignalTypeBase[*_Ts](str):
     """Generic base class for SignalType."""
 
-    name: str
-
-    def __hash__(self) -> int:
-        """Return hash of name."""
-
-        return hash(self.name)
-
-    def __eq__(self, other: object) -> bool:
-        """Check equality for dict keys to be compatible with str."""
-
-        if isinstance(other, str):
-            return self.name == other
-        if isinstance(other, SignalType):
-            return self.name == other.name
-        return False
+    __slots__ = ()
 
 
-@dataclass(frozen=True, eq=False)
 class SignalType[*_Ts](_SignalTypeBase[*_Ts]):
     """Generic string class for signal to improve typing."""
 
+    __slots__ = ()
+
 
-@dataclass(frozen=True, eq=False)
 class SignalTypeFormat[*_Ts](_SignalTypeBase[*_Ts]):
     """Generic string class for signal. Requires call to 'format' before use."""
 
-    def format(self, *args: Any, **kwargs: Any) -> SignalType[*_Ts]:
-        """Format name and return new SignalType instance."""
-        return SignalType(self.name.format(*args, **kwargs))
+    __slots__ = ()

homeassistant/util/signal_type.pyi

@@ -0,0 +1,69 @@
+"""Stub file for signal_type. Provide overload for type checking."""
+# ruff: noqa: PYI021  # Allow docstring
+
+from typing import Any, assert_type
+
+__all__ = [
+    "SignalType",
+    "SignalTypeFormat",
+]
+
+class _SignalTypeBase[*_Ts]:
+    """Custom base class for SignalType. At runtime delegate to str.
+
+    For type checkers pretend to be its own separate class.
+    """
+
+    def __init__(self, value: str, /) -> None: ...
+    def __hash__(self) -> int: ...
+    def __eq__(self, other: object, /) -> bool: ...
+
+class SignalType[*_Ts](_SignalTypeBase[*_Ts]):
+    """Generic string class for signal to improve typing."""
+
+class SignalTypeFormat[*_Ts](_SignalTypeBase[*_Ts]):
+    """Generic string class for signal. Requires call to 'format' before use."""
+
+    def format(self, *args: Any, **kwargs: Any) -> SignalType[*_Ts]: ...
+
+def _test_signal_type_typing() -> None:  # noqa: PYI048
+    """Test SignalType and dispatcher overloads work as intended.
+
+    This is tested during the mypy run. Do not move it to 'tests'!
+    """
+    # pylint: disable=import-outside-toplevel
+    from homeassistant.core import HomeAssistant
+    from homeassistant.helpers.dispatcher import (
+        async_dispatcher_connect,
+        async_dispatcher_send,
+    )
+
+    hass: HomeAssistant
+    def test_func(a: int) -> None: ...
+    def test_func_other(a: int, b: str) -> None: ...
+
+    # No type validation for str signals
+    signal_str = "signal"
+    async_dispatcher_connect(hass, signal_str, test_func)
+    async_dispatcher_connect(hass, signal_str, test_func_other)
+    async_dispatcher_send(hass, signal_str, 2)
+    async_dispatcher_send(hass, signal_str, 2, "Hello World")
+
+    # Using SignalType will perform type validation on target and args
+    signal_1: SignalType[int] = SignalType("signal")
+    assert_type(signal_1, SignalType[int])
+    async_dispatcher_connect(hass, signal_1, test_func)
+    async_dispatcher_connect(hass, signal_1, test_func_other)  # type: ignore[arg-type]
+    async_dispatcher_send(hass, signal_1, 2)
+    async_dispatcher_send(hass, signal_1, "Hello World")  # type: ignore[misc]
+
+    # SignalTypeFormat cannot be used for dispatcher_connect / dispatcher_send
+    # Call format() on it first to convert it to a SignalType
+    signal_format: SignalTypeFormat[int] = SignalTypeFormat("signal_")
+    signal_2 = signal_format.format("2")
+    assert_type(signal_format, SignalTypeFormat[int])
+    assert_type(signal_2, SignalType[int])
+    async_dispatcher_connect(hass, signal_format, test_func)  # type: ignore[call-overload]
+    async_dispatcher_connect(hass, signal_2, test_func)
+    async_dispatcher_send(hass, signal_format, 2)  # type: ignore[call-overload]
+    async_dispatcher_send(hass, signal_2, 2)