lazilly create shutdown event

Author: graingert

src/textual_dev/_compat.py

@@ -0,0 +1,75 @@
+from __future__ import annotations
+
+import sys
+from typing import Any, Generic, TypeVar, overload
+
+__all__ = ["cached_property"]
+
+if sys.version_info >= (3, 12):
+    from functools import cached_property
+else:
+    # based on the code from Python 3.14:
+    # https://github.com/python/cpython/blob/
+    # 5507eff19c757a908a2ff29dfe423e35595fda00/Lib/functools.py#L1089-L1138
+    # Copyright (C) 2006 Python Software Foundation.
+    # vendored under the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2 because
+    # prior to Python 3.12 cached_property used a threading.Lock, which makes
+    # it very slow.
+    _T_co = TypeVar("_T_co", covariant=True)
+    _NOT_FOUND = object()
+
+    class cached_property(Generic[_T_co]):
+        def __init__(self, func: Callable[[Any, _T_co]]) -> None:
+            self.func = func
+            self.attrname = None
+            self.__doc__ = func.__doc__
+            self.__module__ = func.__module__
+
+        def __set_name__(self, owner: type[any], name: str) -> None:
+            if self.attrname is None:
+                self.attrname = name
+            elif name != self.attrname:
+                raise TypeError(
+                    "Cannot assign the same cached_property to two different names "
+                    f"({self.attrname!r} and {name!r})."
+                )
+
+        @overload
+        def __get__(self, instance: None, owner: type[Any] | None = None) -> Self: ...
+
+        @overload
+        def __get__(
+            self, instance: object, owner: type[Any] | None = None
+        ) -> _T_co: ...
+
+        def __get__(
+            self, instance: object, owner: type[Any] | None = None
+        ) -> _T_co | Self:
+            if instance is None:
+                return self
+            if self.attrname is None:
+                raise TypeError(
+                    "Cannot use cached_property instance without calling __set_name__ on it."
+                )
+            try:
+                cache = instance.__dict__
+            except (
+                AttributeError
+            ):  # not all objects have __dict__ (e.g. class defines slots)
+                msg = (
+                    f"No '__dict__' attribute on {type(instance).__name__!r} "
+                    f"instance to cache {self.attrname!r} property."
+                )
+                raise TypeError(msg) from None
+            val = cache.get(self.attrname, _NOT_FOUND)
+            if val is _NOT_FOUND:
+                val = self.func(instance)
+                try:
+                    cache[self.attrname] = val
+                except TypeError:
+                    msg = (
+                        f"The '__dict__' attribute on {type(instance).__name__!r} instance "
+                        f"does not support item assignment for caching {self.attrname!r} property."
+                    )
+                    raise TypeError(msg) from None
+            return val

src/textual_dev/service.py

@@ -18,6 +18,7 @@
 from textual._time import time
 
 from textual_dev.renderables import DevConsoleHeader, DevConsoleLog, DevConsoleNotice
+from textual_dev._compat import cached_property
 
 QUEUEABLE_TYPES = {"client_log", "client_spillover"}
 
@@ -44,9 +45,12 @@ def __init__(
         self.verbose = verbose
         self.exclude = {name.upper() for name in exclude} if exclude else set()
         self.console = Console()
-        self.shutdown_event = asyncio.Event()
         self.clients: list[ClientHandler] = []
 
+    @cached_property
+    def shutdown_event(self) -> asyncio.Event:
+        return asyncio.Event()
+
     async def start(self) -> None:
         """Starts devtools tasks"""
         self.size_poll_task = asyncio.create_task(self._console_size_poller())