enable rule for asyncio, add more details to rule explanation. Extend…

… tests to be more thorough with state management.

docs/rules.rst

@@ -84,7 +84,7 @@ _`ASYNC120` : await-in-except
     This is currently not able to detect asyncio shields.
 
 _`ASYNC121`: control-flow-in-taskgroup
-    `return`, `continue`, and `break` inside a :ref:`taskgroup_nursery` can lead to counterintuitive behaviour. Refactor the code to instead cancel the :ref:`cancel_scope` inside the TaskGroup/Nursery and place the statement outside of the TaskGroup/Nursery block. See `Trio issue #1493 <https://github.com/python-trio/trio/issues/1493>`.
+    `return`, `continue`, and `break` inside a :ref:`taskgroup_nursery` can lead to counterintuitive behaviour. Refactor the code to instead cancel the :ref:`cancel_scope` inside the TaskGroup/Nursery and place the statement outside of the TaskGroup/Nursery block. In asyncio a user might expect the statement to have an immediate effect, but it will wait for all tasks to finish before having an effect. See `Trio issue #1493 <https://github.com/python-trio/trio/issues/1493>` for further issues specific to trio/anyio.
 
 
 Blocking sync calls in async functions

flake8_async/visitors/visitors.py

@@ -371,7 +371,7 @@ def visit_AsyncWith(self, node: ast.AsyncWith):
                 self.unsafe_stack.append("nursery")
             elif get_matching_call(
                 item.context_expr, "create_task_group", base="anyio"
-            ):
+            ) or get_matching_call(item.context_expr, "TaskGroup", base="asyncio"):
                 self.unsafe_stack.append("task group")
 
     def visit_While(self, node: ast.While | ast.For):

tests/eval_files/async121.py

@@ -1,12 +1,21 @@
-# ASYNCIO_NO_ERROR # not a problem in asyncio
+# ASYNCIO_NO_ERROR # checked in async121_asyncio.py
 # ANYIO_NO_ERROR # checked in async121_anyio.py
 
 import trio
 
 
+def condition() -> bool:
+    return False
+
+
 async def foo_return():
     async with trio.open_nursery():
-        return  # ASYNC121: 8, "return", "nursery"
+        if condition():
+            return  # ASYNC121: 12, "return", "nursery"
+        while condition():
+            return  # ASYNC121: 12, "return", "nursery"
+
+    return  # safe
 
 
 async def foo_return_nested():
@@ -26,7 +35,9 @@ async def foo_while_continue_safe():
 async def foo_while_continue_unsafe():
     while True:
         async with trio.open_nursery():
-            continue  # ASYNC121: 12, "continue", "nursery"
+            if condition():
+                continue  # ASYNC121: 16, "continue", "nursery"
+        continue  # safe
 
 
 async def foo_for_continue_safe():
@@ -38,7 +49,9 @@ async def foo_for_continue_safe():
 async def foo_for_continue_unsafe():
     for _ in range(5):
         async with trio.open_nursery():
-            continue  # ASYNC121: 12, "continue", "nursery"
+            if condition():
+                continue  # ASYNC121: 16, "continue", "nursery"
+        continue  # safe
 
 
 # break
@@ -51,7 +64,9 @@ async def foo_while_break_safe():
 async def foo_while_break_unsafe():
     while True:
         async with trio.open_nursery():
-            break  # ASYNC121: 12, "break", "nursery"
+            if condition():
+                break  # ASYNC121: 16, "break", "nursery"
+        continue  # safe
 
 
 async def foo_for_break_safe():
@@ -63,4 +78,20 @@ async def foo_for_break_safe():
 async def foo_for_break_unsafe():
     for _ in range(5):
         async with trio.open_nursery():
-            break  # ASYNC121: 12, "break", "nursery"
+            if condition():
+                break  # ASYNC121: 16, "break", "nursery"
+        continue  # safe
+
+
+# nested nursery
+async def foo_nested_nursery():
+    async with trio.open_nursery():
+        if condition():
+            return  # ASYNC121: 12, "return", "nursery"
+        async with trio.open_nursery():
+            if condition():
+                return  # ASYNC121: 16, "return", "nursery"
+        if condition():
+            return  # ASYNC121: 12, "return", "nursery"
+    if condition():
+        return  # safe

tests/eval_files/async121_anyio.py

@@ -1,4 +1,4 @@
-# ASYNCIO_NO_ERROR # not a problem in asyncio
+# ASYNCIO_NO_ERROR # checked in async121_asyncio.py
 # TRIO_NO_ERROR # checked in async121.py
 # BASE_LIBRARY anyio
 

tests/eval_files/async121_asyncio.py

@@ -0,0 +1,69 @@
+# ANYIO_NO_ERROR
+# TRIO_NO_ERROR # checked in async121.py
+# BASE_LIBRARY asyncio
+# TaskGroup was added in 3.11, we run type checking with 3.9
+# mypy: disable-error-code=attr-defined
+
+import asyncio
+
+
+async def foo_return():
+    async with asyncio.TaskGroup():
+        return  # ASYNC121: 8, "return", "task group"
+
+
+async def foo_return_nested():
+    async with asyncio.TaskGroup():
+
+        def bar():
+            return  # safe
+
+
+# continue
+async def foo_while_continue_safe():
+    async with asyncio.TaskGroup():
+        while True:
+            continue  # safe
+
+
+async def foo_while_continue_unsafe():
+    while True:
+        async with asyncio.TaskGroup():
+            continue  # ASYNC121: 12, "continue", "task group"
+
+
+async def foo_for_continue_safe():
+    async with asyncio.TaskGroup():
+        for _ in range(5):
+            continue  # safe
+
+
+async def foo_for_continue_unsafe():
+    for _ in range(5):
+        async with asyncio.TaskGroup():
+            continue  # ASYNC121: 12, "continue", "task group"
+
+
+# break
+async def foo_while_break_safe():
+    async with asyncio.TaskGroup():
+        while True:
+            break  # safe
+
+
+async def foo_while_break_unsafe():
+    while True:
+        async with asyncio.TaskGroup():
+            break  # ASYNC121: 12, "break", "task group"
+
+
+async def foo_for_break_safe():
+    async with asyncio.TaskGroup():
+        for _ in range(5):
+            break  # safe
+
+
+async def foo_for_break_unsafe():
+    for _ in range(5):
+        async with asyncio.TaskGroup():
+            break  # ASYNC121: 12, "break", "task group"