ASYNC100 no longer triggers on context managers containing a yield (#228)

* ASYNC100 no longer triggers on context managers containing a `yield`

* replace yield with return and enable async910, to fix eval_file noqa

Author: jakkdl

CHANGELOG.md

@@ -1,6 +1,9 @@
 # Changelog
 *[CalVer, YY.month.patch](https://calver.org/)*
 
+## 24.3.6
+- ASYNC100 no longer triggers if a context manager contains a `yield`.
+
 ## 24.3.5
 - ASYNC102 (no await inside finally or critical except) no longer raises warnings for calls to `aclose()` on objects in trio/anyio code. See https://github.com/python-trio/flake8-async/issues/156
 

README.md

@@ -25,7 +25,7 @@ pip install flake8-async
 ## List of warnings
 - **ASYNC100**: A `with [trio/anyio].fail_after(...):` or `with [trio/anyio].move_on_after(...):`
   context does not contain any `await` statements.  This makes it pointless, as
-  the timeout can only be triggered by a checkpoint.
+  the timeout can only be triggered by a checkpoint. This check also allows `yield` statements, since checkpoints can happen in the caller we yield to.
 - **ASYNC101**: `yield` inside a trio/anyio nursery or cancel scope is only safe when implementing a context manager - otherwise, it breaks exception handling.
 - **ASYNC102**: It's unsafe to await inside `finally:` or `except BaseException/trio.Cancelled/anyio.get_cancelled_exc_class()/asyncio.exceptions.CancelledError` unless you use a shielded cancel scope with a timeout. This is currently not able to detect asyncio shields.
 - **ASYNC103**: `except BaseException/trio.Cancelled/anyio.get_cancelled_exc_class()/asyncio.exceptions.CancelledError`, or a bare `except:` with a code path that doesn't re-raise. If you don't want to re-raise `BaseException`, add a separate handler for `trio.Cancelled`/`anyio.get_cancelled_exc_class()`/`asyncio.exceptions.CancelledError` before.

flake8_async/__init__.py

@@ -37,7 +37,7 @@
 
 
 # CalVer: YY.month.patch, e.g. first release of July 2022 == "22.7.1"
-__version__ = "24.3.5"
+__version__ = "24.3.6"
 
 
 # taken from https://github.com/Zac-HD/shed

flake8_async/visitors/visitor100.py

@@ -74,9 +74,11 @@ def visit_For(self, node: cst.For):
         if node.asynchronous is not None:
             self.checkpoint()
 
-    def visit_Await(self, node: cst.Await | cst.For | cst.With):
+    def visit_Await(self, node: cst.Await | cst.Yield):
         self.checkpoint()
 
+    visit_Yield = visit_Await
+
     def visit_FunctionDef(self, node: cst.FunctionDef):
         self.save_state(node, "has_checkpoint_stack", copy=True)
         self.has_checkpoint_stack = []

tests/autofix_files/async100.py

@@ -114,3 +114,9 @@ async def more_nested_tests():
     with contextlib.suppress(Exception):
         with open("blah") as file:
             print("foo")
+
+
+# Don't trigger for blocks with a yield statement
+async def foo():
+    with trio.fail_after(1):
+        yield

tests/autofix_files/noqa.py

@@ -1,47 +1,57 @@
 # AUTOFIX
 # NOASYNCIO - does not trigger on ASYNC100
-# ARG --enable=ASYNC100,ASYNC911
+# ARG --enable=ASYNC100,ASYNC911,ASYNC910
 from typing import Any
 
 import trio
 
 
+def foo() -> bool:
+    return False
+
+
 # fmt: off
 async def foo_no_noqa():
-    await trio.lowlevel.checkpoint()
     # ASYNC100: 9, 'trio', 'fail_after'
-    yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
+    if foo():
+        await trio.lowlevel.checkpoint()
+        return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_bare():
     with trio.fail_after(5):  # noqa
-        yield  # noqa
+        if foo():
+            return  # noqa
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100():
     with trio.fail_after(5):  # noqa: ASYNC100
-        await trio.lowlevel.checkpoint()
-        yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
+        if foo():
+            await trio.lowlevel.checkpoint()
+            return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_911():
     # ASYNC100: 9, 'trio', 'fail_after'
-    yield  # noqa: ASYNC911
+    if foo():
+        return  # noqa: ASYNC910
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100_911():
     with trio.fail_after(5):  # noqa: ASYNC100, ASYNC911
-        yield  # noqa: ASYNC911
+        if foo():
+            return  # noqa: ASYNC910
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100_911_500():
     with trio.fail_after(5):  # noqa: ASYNC100, ASYNC911 , ASYNC500,,,
-        yield  # noqa: ASYNC100, ASYNC911 , ASYNC500,,,
+        if foo():
+            return  # noqa: ASYNC100, ASYNC910 , ASYNC500,,,
     await trio.lowlevel.checkpoint()
 # fmt: on
 

tests/autofix_files/noqa.py.diff

@@ -1,31 +1,35 @@
 ---
 +++
-@@ x,8 x,9 @@
+@@ x,9 x,10 @@
 
  # fmt: off
  async def foo_no_noqa():
 -    with trio.fail_after(5):  # ASYNC100: 9, 'trio', 'fail_after'
--        yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
-+    await trio.lowlevel.checkpoint()
+-        if foo():
+-            return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
 +    # ASYNC100: 9, 'trio', 'fail_after'
-+    yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
++    if foo():
++        await trio.lowlevel.checkpoint()
++        return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
      await trio.lowlevel.checkpoint()
 
 
-@@ x,13 x,14 @@
-
+@@ x,14 x,15 @@
  async def foo_noqa_100():
      with trio.fail_after(5):  # noqa: ASYNC100
-+        await trio.lowlevel.checkpoint()
-         yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
+         if foo():
++            await trio.lowlevel.checkpoint()
+             return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
      await trio.lowlevel.checkpoint()
 
 
  async def foo_noqa_911():
 -    with trio.fail_after(5):  # ASYNC100: 9, 'trio', 'fail_after'
--        yield  # noqa: ASYNC911
+-        if foo():
+-            return  # noqa: ASYNC910
 +    # ASYNC100: 9, 'trio', 'fail_after'
-+    yield  # noqa: ASYNC911
++    if foo():
++        return  # noqa: ASYNC910
      await trio.lowlevel.checkpoint()
 
 

tests/eval_files/async100.py

@@ -114,3 +114,9 @@ async def more_nested_tests():
     with contextlib.suppress(Exception):
         with open("blah") as file:
             print("foo")
+
+
+# Don't trigger for blocks with a yield statement
+async def foo():
+    with trio.fail_after(1):
+        yield

tests/eval_files/noqa.py

@@ -1,45 +1,55 @@
 # AUTOFIX
 # NOASYNCIO - does not trigger on ASYNC100
-# ARG --enable=ASYNC100,ASYNC911
+# ARG --enable=ASYNC100,ASYNC911,ASYNC910
 from typing import Any
 
 import trio
 
 
+def foo() -> bool:
+    return False
+
+
 # fmt: off
 async def foo_no_noqa():
     with trio.fail_after(5):  # ASYNC100: 9, 'trio', 'fail_after'
-        yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
+        if foo():
+            return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_bare():
     with trio.fail_after(5):  # noqa
-        yield  # noqa
+        if foo():
+            return  # noqa
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100():
     with trio.fail_after(5):  # noqa: ASYNC100
-        yield  # ASYNC911: 8, "yield", Statement("function definition", lineno-2)
+        if foo():
+            return  # ASYNC910: 12, "return", Statement("function definition", lineno-3)
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_911():
     with trio.fail_after(5):  # ASYNC100: 9, 'trio', 'fail_after'
-        yield  # noqa: ASYNC911
+        if foo():
+            return  # noqa: ASYNC910
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100_911():
     with trio.fail_after(5):  # noqa: ASYNC100, ASYNC911
-        yield  # noqa: ASYNC911
+        if foo():
+            return  # noqa: ASYNC910
     await trio.lowlevel.checkpoint()
 
 
 async def foo_noqa_100_911_500():
     with trio.fail_after(5):  # noqa: ASYNC100, ASYNC911 , ASYNC500,,,
-        yield  # noqa: ASYNC100, ASYNC911 , ASYNC500,,,
+        if foo():
+            return  # noqa: ASYNC100, ASYNC910 , ASYNC500,,,
     await trio.lowlevel.checkpoint()
 # fmt: on