Improve replacement (#345)

* make ASYNC912 and 913 care about cancel points, and ignore schedule points

* delete now redundant eval files, fix async113 false alarm on [not trio].serve_listeners etc

Author: jakkdl

docs/changelog.rst

@@ -4,6 +4,10 @@ Changelog
 
 `CalVer, YY.month.patch <https://calver.org/>`_
 
+25.2.2
+=======
+- :ref:`ASYNC113 <async113>` now only triggers on ``trio.[serve_tcp, serve_ssl_over_tcp, serve_listeners, run_process]``, instead of accepting anything as the attribute base. (e.g. :func:`anyio.run_process` is not startable).
+
 25.2.1
 =======
 - :ref:`ASYNC912 <async912>` and :ref:`ASYNC913 <async913>` will now trigger if there's no *cancel* points. This means that :func:`trio.open_nursery`/`anyio.create_task_group` will not silence them on their own, unless they're guaranteed to start tasks.

docs/usage.rst

@@ -33,7 +33,7 @@ adding the following to your ``.pre-commit-config.yaml``:
    minimum_pre_commit_version: '2.9.0'
    repos:
    - repo: https://github.com/python-trio/flake8-async
-     rev: 25.2.1
+     rev: 25.2.2
      hooks:
        - id: flake8-async
          # args: [--enable=ASYNC, --disable=ASYNC9, --autofix=ASYNC]

flake8_async/__init__.py

@@ -38,7 +38,7 @@
 
 
 # CalVer: YY.month.patch, e.g. first release of July 2022 == "22.7.1"
-__version__ = "25.2.1"
+__version__ = "25.2.2"
 
 
 # taken from https://github.com/Zac-HD/shed

flake8_async/visitors/visitors.py

@@ -121,10 +121,10 @@ def visit_With(self, node: ast.With | ast.AsyncWith):
             elif get_matching_call(
                 item.context_expr, "create_task_group", base="anyio"
             ):
-                nursery_type = "taskgroup"
+                nursery_type = "task group"
             # check for asyncio.TaskGroup
             elif get_matching_call(item.context_expr, "TaskGroup", base="asyncio"):
-                nursery_type = "taskgroup"
+                nursery_type = "task group"
                 start_methods = ("create_task",)
             else:
                 # incorrectly marked as not covered on py39
@@ -151,12 +151,12 @@ def visit_With(self, node: ast.With | ast.AsyncWith):
 
 
 # used in 113 and 114
-STARTABLE_CALLS = (
+STARTABLE_CALLS = ("serve",)
+TRIO_STARTABLE_CALLS = (
     "run_process",
     "serve_ssl_over_tcp",
     "serve_tcp",
     "serve_listeners",
-    "serve",
 )
 
 
@@ -201,7 +201,11 @@ def is_startable(n: ast.expr, *startable_list: str) -> bool:
             if isinstance(n, ast.Name):
                 return n.id in startable_list
             if isinstance(n, ast.Attribute):
-                return n.attr in startable_list
+                return n.attr in startable_list and not (
+                    n.attr in TRIO_STARTABLE_CALLS
+                    and isinstance(n.value, ast.Name)
+                    and n.value.id != "trio"
+                )
             if isinstance(n, ast.Call):
                 return any(is_startable(nn, *startable_list) for nn in n.args)
             return False
@@ -213,12 +217,16 @@ def is_nursery_call(node: ast.expr):
             ):
                 return False
             var = ast.unparse(node.value)
-            return ("trio" in self.library and var.endswith("nursery")) or (
-                self.variables.get(var, "")
-                in (
-                    "trio.Nursery",
-                    "anyio.TaskGroup",
-                    "asyncio.TaskGroup",
+            return (
+                ("trio" in self.library and var.endswith("nursery"))
+                or ("anyio" in self.library and var.endswith("task_group"))
+                or (
+                    self.variables.get(var, "")
+                    in (
+                        "trio.Nursery",
+                        "anyio.TaskGroup",
+                        "asyncio.TaskGroup",
+                    )
                 )
             )
 
@@ -229,6 +237,7 @@ def is_nursery_call(node: ast.expr):
             and is_startable(
                 node.args[0],
                 *STARTABLE_CALLS,
+                *TRIO_STARTABLE_CALLS,
                 *self.options.startable_in_context_manager,
             )
         ):
@@ -254,7 +263,11 @@ def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef):
             for n in self.walk(*node.args.args, *node.args.kwonlyargs)
         ) and not any(
             node.name == opt
-            for opt in (*self.options.startable_in_context_manager, *STARTABLE_CALLS)
+            for opt in (
+                *self.options.startable_in_context_manager,
+                *STARTABLE_CALLS,
+                *TRIO_STARTABLE_CALLS,
+            )
         ):
             self.error(node, node.name)
 

tests/autofix_files/async100.py

@@ -140,3 +140,77 @@ async def dont_crash_on_non_name_or_attr_call():
 async def another_weird_with_call():
     async with a().b():
         ...
+
+
+# ---open_nursery / create_task_group stuff---
+
+
+async def nursery_no_cancel_point():
+    # error: 9, "trio", "CancelScope"
+    async with trio.open_nursery():
+        ...
+
+
+# but it is a cancel point if the nursery contains a call to start_soon()
+
+
+async def nursery_start_soon():
+    with trio.CancelScope():
+        async with trio.open_nursery() as n:
+            n.start_soon(trio.sleep, 0)
+
+
+async def nursery_start_soon_misnested():
+    async with trio.open_nursery() as n:
+        # error: 13, "trio", "CancelScope"
+        n.start_soon(trio.sleep, 0)
+
+
+async def nested_scope():
+    with trio.CancelScope():
+        with trio.CancelScope():
+            async with trio.open_nursery() as n:
+                n.start_soon(trio.sleep, 0)
+
+
+async def nested_nursery():
+    with trio.CancelScope():
+        async with trio.open_nursery() as n:
+            async with trio.open_nursery() as n2:
+                n2.start_soon(trio.sleep, 0)
+
+
+async def nested_function_call():
+
+    # error: 9, "trio", "CancelScope"
+    async with trio.open_nursery() as n:
+
+        def foo():
+            n.start_soon(trio.sleep, 0)
+
+        # a false alarm in case we call foo()... but we can't check if they do
+        foo()
+
+
+# insert cancel point on nursery exit, not at the start_soon call
+async def cancel_point_on_nursery_exit():
+    with trio.CancelScope():
+        async with trio.open_nursery() as n:
+            # error: 17, "trio", "CancelScope"
+            n.start_soon(trio.sleep, 0)
+
+
+# async100 does not consider *redundant* cancel scopes
+async def redundant_cancel_scope():
+    with trio.CancelScope():
+        with trio.CancelScope():
+            await trio.lowlevel.checkpoint()
+
+
+# but if it did then none of these scopes should be marked redundant
+# The inner checks task startup, the outer checks task exit
+async def nursery_exit_blocks_with_start():
+    with trio.CancelScope():
+        async with trio.open_nursery() as n:
+            with trio.CancelScope():
+                await n.start(trio.sleep, 0)

tests/autofix_files/async100.py.diff

@@ -96,14 +96,15 @@
              await trio.sleep_forever()
 -        with trio.CancelScope():  # error: 13, "trio", "CancelScope"
 -            ...
-+        # error: 13, "trio", "CancelScope"
-+        ...
-
+-
 -    with trio.fail_after(1):  # error: 9, "trio", "fail_after"
 -        with trio.CancelScope():  # error: 13, "trio", "CancelScope"
 -            ...
 -        with trio.CancelScope():  # error: 13, "trio", "CancelScope"
 -            ...
++        # error: 13, "trio", "CancelScope"
++        ...
++
 +    # error: 9, "trio", "fail_after"
 +    # error: 13, "trio", "CancelScope"
 +    ...
@@ -119,14 +120,72 @@
 -    with trio.fail_after(1):  # error: 9, "trio", "fail_after"
 -        with contextlib.suppress(Exception):
 -            print("foo")
-+    # error: 9, "trio", "fail_after"
-     with contextlib.suppress(Exception):
+-    with contextlib.suppress(Exception):
 -        with trio.fail_after(1):  # error: 13, "trio", "fail_after"
 -            print("foo")
++    # error: 9, "trio", "fail_after"
++    with contextlib.suppress(Exception):
 +        print("foo")
 +    with contextlib.suppress(Exception):
 +        # error: 13, "trio", "fail_after"
 +        print("foo")
 
      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 trio.open_nursery():
+-            ...
++    # error: 9, "trio", "CancelScope"
++    async with trio.open_nursery():
++        ...
+
+
+ # but it is a cancel point if the nursery contains a call to start_soon()
+@@ x,8 x,8 @@
+
+ async def nursery_start_soon_misnested():
+     async with trio.open_nursery() as n:
+-        with trio.CancelScope():  # error: 13, "trio", "CancelScope"
+-            n.start_soon(trio.sleep, 0)
++        # error: 13, "trio", "CancelScope"
++        n.start_soon(trio.sleep, 0)
+
+
+ async def nested_scope():
+@@ x,22 x,22 @@
+
+ async def nested_function_call():
+
+-    with trio.CancelScope():  # error: 9, "trio", "CancelScope"
+-        async with trio.open_nursery() as n:
+-
+-            def foo():
+-                n.start_soon(trio.sleep, 0)
+-
+-            # a false alarm in case we call foo()... but we can't check if they do
+-            foo()
++    # error: 9, "trio", "CancelScope"
++    async with trio.open_nursery() as n:
++
++        def foo():
++            n.start_soon(trio.sleep, 0)
++
++        # a false alarm in case we call foo()... but we can't check if they do
++        foo()
+
+
+ # insert cancel point on nursery exit, not at the start_soon call
+ async def cancel_point_on_nursery_exit():
+     with trio.CancelScope():
+         async with trio.open_nursery() as n:
+-            with trio.CancelScope():  # error: 17, "trio", "CancelScope"
+-                n.start_soon(trio.sleep, 0)
++            # error: 17, "trio", "CancelScope"
++            n.start_soon(trio.sleep, 0)
+
+
+ # async100 does not consider *redundant* cancel scopes