async100 now ignores trio.open_nursery and anyio.create_task_group

docs/changelog.rst

@@ -4,6 +4,10 @@ Changelog
 
 `CalVer, YY.month.patch <https://calver.org/>`_
 
+24.11.1
+======
+- :ref:`ASYNC100 <async100>` now ignores :func:`trio.open_nursery` and :func:`anyio.create_task_group` as cancellation sources.
+
 24.10.2
 =======
 - :ref:`ASYNC102 <async102>` now also warns about ``await()`` inside ``__aexit__``.

flake8_async/__init__.py

@@ -38,7 +38,7 @@
 
 
 # CalVer: YY.month.patch, e.g. first release of July 2022 == "22.7.1"
-__version__ = "24.10.2"
+__version__ = "24.11.1"
 
 
 # taken from https://github.com/Zac-HD/shed

flake8_async/visitors/visitor91x.py

@@ -25,6 +25,7 @@
     flatten_preserving_comments,
     fnmatch_qualified_name_cst,
     func_has_decorator,
+    identifier_to_string,
     iter_guaranteed_once_cst,
     with_has_call,
 )
@@ -491,12 +492,34 @@ def _is_exception_suppressing_context_manager(self, node: cst.With) -> bool:
             is not None
         )
 
+    def _checkpoint_with(self, node: cst.With):
+        """Conditionally checkpoints entry/exit of With.
+
+        If the with only contains calls to open_nursery/create_task_group, it's a schedule
+        point but not a cancellation point, so we treat it as a checkpoint for async91x
+        but not for async100.
+        """
+        if getattr(node, "asynchronous", None):
+            for item in node.items:
+                if not isinstance(item.item, cst.Call) or not isinstance(
+                    item.item.func, (cst.Attribute, cst.Name)
+                ):
+                    self.checkpoint()
+                    break
+
+                func = identifier_to_string(item.item.func)
+                assert func is not None
+                if func not in ("trio.open_nursery", "anyio.create_task_group"):
+                    self.checkpoint()
+                    break
+            else:
+                self.uncheckpointed_statements = set()
+
     # Async context managers can reasonably checkpoint on either or both of entry and
     # exit.  Given that we can't tell which, we assume "both" to avoid raising a
     # missing-checkpoint warning when there might in fact be one (i.e. a false alarm).
     def visit_With_body(self, node: cst.With):
-        if getattr(node, "asynchronous", None):
-            self.checkpoint()
+        self._checkpoint_with(node)
 
         # if this might suppress exceptions, we cannot treat anything inside it as
         # checkpointing.
@@ -555,8 +578,7 @@ def leave_With(self, original_node: cst.With, updated_node: cst.With):
             self.restore_state(original_node)
             self.uncheckpointed_statements.update(prev_checkpoints)
 
-        if getattr(original_node, "asynchronous", None):
-            self.checkpoint()
+        self._checkpoint_with(original_node)
         return updated_node
 
     # error if no checkpoint since earlier yield or function entry

tests/autofix_files/async100.py

@@ -130,3 +130,14 @@ async def fn(timeout):
             if condition():
                 return
             await trio.sleep(1)
+
+
+async def nursery_no_cancel_point():
+    # error: 9, "trio", "CancelScope"
+    async with anyio.create_task_group():
+        ...
+
+
+async def dont_crash_on_non_name_or_attr_call():
+    async with contextlib.asynccontextmanager(agen_fn)():
+        ...

tests/autofix_files/async100.py.diff

@@ -130,3 +130,16 @@
 
      with contextlib.suppress(Exception):
          with open("blah") as file:
+@@ x,9 x,9 @@
+
+
+ async def nursery_no_cancel_point():
+-    with trio.CancelScope():  # error: 9, "trio", "CancelScope"
+-        async with anyio.create_task_group():
+-            ...
++    # error: 9, "trio", "CancelScope"
++    async with anyio.create_task_group():
++        ...
+
+
+ async def dont_crash_on_non_name_or_attr_call():

tests/autofix_files/async100_trio.py

@@ -0,0 +1,10 @@
+# AUTOFIX
+# ASYNCIO_NO_ERROR # asyncio.open_nursery doesn't exist
+# ANYIO_NO_ERROR # anyio.open_nursery doesn't exist
+import trio
+
+
+async def nursery_no_cancel_point():
+    # error: 9, "trio", "CancelScope"
+    async with trio.open_nursery():
+        ...

tests/autofix_files/async100_trio.py.diff

@@ -0,0 +1,12 @@
+---
++++
+@@ x,6 x,6 @@
+
+
+ async def nursery_no_cancel_point():
+-    with trio.CancelScope():  # error: 9, "trio", "CancelScope"
+-        async with trio.open_nursery():
+-            ...
++    # error: 9, "trio", "CancelScope"
++    async with trio.open_nursery():
++        ...

tests/eval_files/async100.py

@@ -130,3 +130,14 @@ async def fn(timeout):
             if condition():
                 return
             await trio.sleep(1)
+
+
+async def nursery_no_cancel_point():
+    with trio.CancelScope():  # error: 9, "trio", "CancelScope"
+        async with anyio.create_task_group():
+            ...
+
+
+async def dont_crash_on_non_name_or_attr_call():
+    async with contextlib.asynccontextmanager(agen_fn)():
+        ...

tests/eval_files/async100_trio.py

@@ -0,0 +1,10 @@
+# AUTOFIX
+# ASYNCIO_NO_ERROR # asyncio.open_nursery doesn't exist
+# ANYIO_NO_ERROR # anyio.open_nursery doesn't exist
+import trio
+
+
+async def nursery_no_cancel_point():
+    with trio.CancelScope():  # error: 9, "trio", "CancelScope"
+        async with trio.open_nursery():
+            ...