Use asyncio.timeout instead of asyncio.wait_for.

asyncio.wait_for creates a task whereas asyncio.timeout doesn't.

Fallback to a vendored version of async_timeout on Python < 3.11.

async.timeout will become the underlying implementation for
async.wait_for in Python 3.12:
python/cpython#98518

pyproject.toml

@@ -39,6 +39,7 @@ branch = true
 omit = [
     # */websockets matches src/websockets and .tox/**/site-packages/websockets
     "*/websockets/__main__.py",
+    "*/websockets/legacy/async_timeout.py",
     "*/websockets/legacy/compatibility.py",
     "tests/maxi_cov.py",
 ]

src/websockets/legacy/async_timeout.py

@@ -0,0 +1,225 @@
+# From https://github.com/aio-libs/async-timeout/blob/master/async_timeout/__init__.py
+# Licensed under the Apache License, Version 2.0.
+
+import asyncio
+import enum
+import sys
+import warnings
+from types import TracebackType
+from typing import Optional, Type
+
+
+if sys.version_info >= (3, 8):
+    from typing import final
+else:
+    from typing_extensions import final
+
+
+__version__ = "4.0.2"
+
+
+__all__ = ("timeout", "timeout_at", "Timeout")
+
+
+def timeout(delay: Optional[float]) -> "Timeout":
+    """timeout context manager.
+
+    Useful in cases when you want to apply timeout logic around block
+    of code or in cases when asyncio.wait_for is not suitable. For example:
+
+    >>> async with timeout(0.001):
+    ...     async with aiohttp.get('https://github.com') as r:
+    ...         await r.text()
+
+
+    delay - value in seconds or None to disable timeout logic
+    """
+    loop = asyncio.get_running_loop()
+    if delay is not None:
+        deadline = loop.time() + delay  # type: Optional[float]
+    else:
+        deadline = None
+    return Timeout(deadline, loop)
+
+
+def timeout_at(deadline: Optional[float]) -> "Timeout":
+    """Schedule the timeout at absolute time.
+
+    deadline argument points on the time in the same clock system
+    as loop.time().
+
+    Please note: it is not POSIX time but a time with
+    undefined starting base, e.g. the time of the system power on.
+
+    >>> async with timeout_at(loop.time() + 10):
+    ...     async with aiohttp.get('https://github.com') as r:
+    ...         await r.text()
+
+
+    """
+    loop = asyncio.get_running_loop()
+    return Timeout(deadline, loop)
+
+
+class _State(enum.Enum):
+    INIT = "INIT"
+    ENTER = "ENTER"
+    TIMEOUT = "TIMEOUT"
+    EXIT = "EXIT"
+
+
+@final
+class Timeout:
+    # Internal class, please don't instantiate it directly
+    # Use timeout() and timeout_at() public factories instead.
+    #
+    # Implementation note: `async with timeout()` is preferred
+    # over `with timeout()`.
+    # While technically the Timeout class implementation
+    # doesn't need to be async at all,
+    # the `async with` statement explicitly points that
+    # the context manager should be used from async function context.
+    #
+    # This design allows to avoid many silly misusages.
+    #
+    # TimeoutError is raised immediately when scheduled
+    # if the deadline is passed.
+    # The purpose is to time out as soon as possible
+    # without waiting for the next await expression.
+
+    __slots__ = ("_deadline", "_loop", "_state", "_timeout_handler")
+
+    def __init__(
+        self, deadline: Optional[float], loop: asyncio.AbstractEventLoop
+    ) -> None:
+        self._loop = loop
+        self._state = _State.INIT
+
+        self._timeout_handler = None  # type: Optional[asyncio.Handle]
+        if deadline is None:
+            self._deadline = None  # type: Optional[float]
+        else:
+            self.update(deadline)
+
+    def __enter__(self) -> "Timeout":
+        warnings.warn(
+            "with timeout() is deprecated, use async with timeout() instead",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        self._do_enter()
+        return self
+
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        exc_tb: Optional[TracebackType],
+    ) -> Optional[bool]:
+        self._do_exit(exc_type)
+        return None
+
+    async def __aenter__(self) -> "Timeout":
+        self._do_enter()
+        return self
+
+    async def __aexit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        exc_tb: Optional[TracebackType],
+    ) -> Optional[bool]:
+        self._do_exit(exc_type)
+        return None
+
+    @property
+    def expired(self) -> bool:
+        """Is timeout expired during execution?"""
+        return self._state == _State.TIMEOUT
+
+    @property
+    def deadline(self) -> Optional[float]:
+        return self._deadline
+
+    def reject(self) -> None:
+        """Reject scheduled timeout if any."""
+        # cancel is maybe better name but
+        # task.cancel() raises CancelledError in asyncio world.
+        if self._state not in (_State.INIT, _State.ENTER):
+            raise RuntimeError(f"invalid state {self._state.value}")
+        self._reject()
+
+    def _reject(self) -> None:
+        if self._timeout_handler is not None:
+            self._timeout_handler.cancel()
+            self._timeout_handler = None
+
+    def shift(self, delay: float) -> None:
+        """Advance timeout on delay seconds.
+
+        The delay can be negative.
+
+        Raise RuntimeError if shift is called when deadline is not scheduled
+        """
+        deadline = self._deadline
+        if deadline is None:
+            raise RuntimeError("cannot shift timeout if deadline is not scheduled")
+        self.update(deadline + delay)
+
+    def update(self, deadline: float) -> None:
+        """Set deadline to absolute value.
+
+        deadline argument points on the time in the same clock system
+        as loop.time().
+
+        If new deadline is in the past the timeout is raised immediately.
+
+        Please note: it is not POSIX time but a time with
+        undefined starting base, e.g. the time of the system power on.
+        """
+        if self._state == _State.EXIT:
+            raise RuntimeError("cannot reschedule after exit from context manager")
+        if self._state == _State.TIMEOUT:
+            raise RuntimeError("cannot reschedule expired timeout")
+        if self._timeout_handler is not None:
+            self._timeout_handler.cancel()
+        self._deadline = deadline
+        if self._state != _State.INIT:
+            self._reschedule()
+
+    def _reschedule(self) -> None:
+        assert self._state == _State.ENTER
+        deadline = self._deadline
+        if deadline is None:
+            return
+
+        now = self._loop.time()
+        if self._timeout_handler is not None:
+            self._timeout_handler.cancel()
+
+        task = asyncio.current_task()
+        if deadline <= now:
+            self._timeout_handler = self._loop.call_soon(self._on_timeout, task)
+        else:
+            self._timeout_handler = self._loop.call_at(deadline, self._on_timeout, task)
+
+    def _do_enter(self) -> None:
+        if self._state != _State.INIT:
+            raise RuntimeError(f"invalid state {self._state.value}")
+        self._state = _State.ENTER
+        self._reschedule()
+
+    def _do_exit(self, exc_type: Optional[Type[BaseException]]) -> None:
+        if exc_type is asyncio.CancelledError and self._state == _State.TIMEOUT:
+            self._timeout_handler = None
+            raise asyncio.TimeoutError
+        # timeout has not expired
+        self._state = _State.EXIT
+        self._reject()
+        return None
+
+    def _on_timeout(self, task: "asyncio.Task[None]") -> None:
+        task.cancel()
+        self._state = _State.TIMEOUT
+        # drop the reference early
+        self._timeout_handler = None

src/websockets/legacy/compatibility.py

@@ -5,6 +5,9 @@
 from typing import Any, Dict
 
 
+__all__ = ["asyncio_timeout", "loop_if_py_lt_38"]
+
+
 if sys.version_info[:2] >= (3, 8):
 
     def loop_if_py_lt_38(loop: asyncio.AbstractEventLoop) -> Dict[str, Any]:
@@ -22,3 +25,9 @@ def loop_if_py_lt_38(loop: asyncio.AbstractEventLoop) -> Dict[str, Any]:
 
         """
         return {"loop": loop}
+
+
+if sys.version_info[:2] >= (3, 11):
+    from asyncio import timeout as asyncio_timeout  # noqa: F401
+else:
+    from .async_timeout import timeout as asyncio_timeout  # noqa: F401

src/websockets/legacy/protocol.py

@@ -53,7 +53,7 @@
 )
 from ..protocol import State
 from ..typing import Data, LoggerLike, Subprotocol
-from .compatibility import loop_if_py_lt_38
+from .compatibility import asyncio_timeout, loop_if_py_lt_38
 from .framing import Frame
 
 
@@ -761,19 +761,16 @@ async def close(self, code: int = 1000, reason: str = "") -> None:
 
         """
         try:
-            await asyncio.wait_for(
-                self.write_close_frame(Close(code, reason)),
-                self.close_timeout,
-                **loop_if_py_lt_38(self.loop),
-            )
+            async with asyncio_timeout(self.close_timeout):
+                await self.write_close_frame(Close(code, reason))
         except asyncio.TimeoutError:
             # If the close frame cannot be sent because the send buffers
             # are full, the closing handshake won't complete anyway.
             # Fail the connection to shut down faster.
             self.fail_connection()
 
-        # If no close frame is received within the timeout, wait_for() cancels
-        # the data transfer task and raises TimeoutError.
+        # If no close frame is received within the timeout, asyncio_timeout()
+        # cancels the data transfer task and raises TimeoutError.
 
         # If close() is called multiple times concurrently and one of these
         # calls hits the timeout, the data transfer task will be canceled.
@@ -782,11 +779,8 @@ async def close(self, code: int = 1000, reason: str = "") -> None:
         try:
             # If close() is canceled during the wait, self.transfer_data_task
             # is canceled before the timeout elapses.
-            await asyncio.wait_for(
-                self.transfer_data_task,
-                self.close_timeout,
-                **loop_if_py_lt_38(self.loop),
-            )
+            async with asyncio_timeout(self.close_timeout):
+                await self.transfer_data_task
         except (asyncio.TimeoutError, asyncio.CancelledError):
             pass
 
@@ -1268,11 +1262,8 @@ async def keepalive_ping(self) -> None:
 
                 if self.ping_timeout is not None:
                     try:
-                        await asyncio.wait_for(
-                            pong_waiter,
-                            self.ping_timeout,
-                            **loop_if_py_lt_38(self.loop),
-                        )
+                        async with asyncio_timeout(self.ping_timeout):
+                            await pong_waiter
                         self.logger.debug("% received keepalive pong")
                     except asyncio.TimeoutError:
                         if self.debug:
@@ -1384,11 +1375,8 @@ async def wait_for_connection_lost(self) -> bool:
         """
         if not self.connection_lost_waiter.done():
             try:
-                await asyncio.wait_for(
-                    asyncio.shield(self.connection_lost_waiter),
-                    self.close_timeout,
-                    **loop_if_py_lt_38(self.loop),
-                )
+                async with asyncio_timeout(self.close_timeout):
+                    await asyncio.shield(self.connection_lost_waiter)
             except asyncio.TimeoutError:
                 pass
         # Re-check self.connection_lost_waiter.done() synchronously because