Fixed __exit__() return type of various context managers (#849)

---------

Co-authored-by: Alex Grönholm <[email protected]>

docs/versionhistory.rst

@@ -13,6 +13,8 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
   (`#836 <https://github.com/agronholm/anyio/pull/836>`_; PR by @graingert)
 - Fixed ``AssertionError`` when using ``nest-asyncio``
   (`#840 <https://github.com/agronholm/anyio/issues/840>`_)
+- Fixed return type annotation of various context managers' ``__exit__`` method
+  (`#847 <https://github.com/agronholm/anyio/issues/847>`_; PR by @Enegg)
 
 **4.7.0**
 

src/anyio/_backends/_asyncio.py

@@ -449,7 +449,7 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
+    ) -> bool:
         del exc_tb
 
         if not self._active:
@@ -2116,10 +2116,9 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
+    ) -> None:
         for sig in self._handled_signals:
             self._loop.remove_signal_handler(sig)
-        return None
 
     def __aiter__(self) -> _SignalReceiver:
         return self
@@ -2448,7 +2447,7 @@ def create_capacity_limiter(cls, total_tokens: float) -> abc.CapacityLimiter:
         return CapacityLimiter(total_tokens)
 
     @classmethod
-    async def run_sync_in_worker_thread(
+    async def run_sync_in_worker_thread(  # type: ignore[return]
         cls,
         func: Callable[[Unpack[PosArgsT]], T_Retval],
         args: tuple[Unpack[PosArgsT]],
@@ -2470,7 +2469,7 @@ async def run_sync_in_worker_thread(
 
         async with limiter or cls.current_default_thread_limiter():
             with CancelScope(shield=not abandon_on_cancel) as scope:
-                future: asyncio.Future = asyncio.Future()
+                future = asyncio.Future[T_Retval]()
                 root_task = find_root_task()
                 if not idle_workers:
                     worker = WorkerThread(root_task, workers, idle_workers)

src/anyio/_backends/_trio.py

@@ -132,8 +132,7 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
-        # https://github.com/python-trio/trio-typing/pull/79
+    ) -> bool:
         return self.__original.__exit__(exc_type, exc_val, exc_tb)
 
     def cancel(self) -> None:
@@ -186,9 +185,10 @@ async def __aexit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
+    ) -> bool:
         try:
-            return await self._nursery_manager.__aexit__(exc_type, exc_val, exc_tb)
+            # trio.Nursery.__exit__ returns bool; .open_nursery has wrong type
+            return await self._nursery_manager.__aexit__(exc_type, exc_val, exc_tb)  # type: ignore[return-value]
         except BaseExceptionGroup as exc:
             if not exc.split(trio.Cancelled)[1]:
                 raise trio.Cancelled._create() from exc

src/anyio/_core/_synchronization.py

@@ -728,6 +728,5 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
+    ) -> None:
         self._guarded = False
-        return None

src/anyio/_core/_tasks.py

@@ -88,7 +88,7 @@ def __exit__(
         exc_type: type[BaseException] | None,
         exc_val: BaseException | None,
         exc_tb: TracebackType | None,
-    ) -> bool | None:
+    ) -> bool:
         raise NotImplementedError
 
 

src/anyio/to_process.py

@@ -35,7 +35,7 @@
 _default_process_limiter: RunVar[CapacityLimiter] = RunVar("_default_process_limiter")
 
 
-async def run_sync(
+async def run_sync(  # type: ignore[return]
     func: Callable[[Unpack[PosArgsT]], T_Retval],
     *args: Unpack[PosArgsT],
     cancellable: bool = False,

tests/test_taskgroups.py

@@ -865,7 +865,8 @@ async def task(task_status: TaskStatus) -> NoReturn:
             completed = True
             scope.shield = False
             await sleep(1)
-            pytest.fail("Execution should not reach this point")
+
+        pytest.fail("Execution should not reach this point")
 
     async with create_task_group() as tg:
         await tg.start(task)