eyyy stuff just works now

Author: jakkdl

flake8_async/visitors/visitors.py

@@ -254,22 +254,17 @@ def is_nursery_call(node: ast.expr) -> str | None:
                 self.potential_errors[var].append(node)
 
     def visit_AsyncWith(self, node: ast.AsyncWith | ast.With):
-        self.visit_nodes(node.items)
-        self.visit_nodes(node.body)
-        for item in node.items:
-            if (
-                get_matching_call(item.context_expr, "open_nursery", base="trio")
-                or get_matching_call(
-                    item.context_expr, "create_task_group", base="anyio"
-                )
-                or get_matching_call(item.context_expr, "TaskGroup", base="asyncio")
-            ) and isinstance(item.optional_vars, ast.Name):
-
-                self.potential_errors.pop(item.optional_vars.id, None)
+        # Entirely skip any nurseries that doesn't have any yields in them.
+        # This fixes an otherwise very thorny false alarm.
+        # In the worst case this does mean we iterate over the body twice, but might
+        # actually be a performance gain on average due to setting `novisit`
+        if not any(isinstance(n, ast.Yield) for b in node.body for n in ast.walk(b)):
+            self.novisit = True
+            return
 
     # open_nursery/create_task_group only works with AsyncWith, but in case somebody
-    # is doing something very weird we'll be conservative and possibly clear
-    # some potential errors
+    # is doing something very weird we'll be conservative and possibly avoid
+    # some potential false alarms
     visit_With = visit_AsyncWith
 
 

tests/eval_files/async113.py

@@ -150,11 +150,10 @@ async def false_alarm():
     yield
 
 
-# this would ideally error, but not worth the extra logic
 @asynccontextmanager
 async def should_error():
     async with trio.open_nursery() as nursery:
-        nursery.start_soon(my_startable)
+        nursery.start_soon(my_startable)  # ASYNC113: 8
         # overrides the nursery variable
         async with trio.open_nursery() as nursery:
             nursery.start_soon(my_startable)
@@ -169,14 +168,25 @@ async def foo_sync_with_closed():
     yield
 
 
-# this one is surprisingly hard to fix
-# the easiest way would be with a leave_AsyncFunctionDef, but that's only a thing in
-# cst visitors; and we can't do the standard thing of manually visiting children in
-# visit_AsyncFunctionDef because we need the interleaving of the utility visitor.
-# So I either need to convert the visitor to cst, including VisitorTypeTracker, or
-# add logic to Flake8AsyncRunner to also support leave_XXX.
-# The latter is probably not too bad but... a tomorrow problem
+# fixed by entirely skipping nurseries without yields in them
 class FalseAlarm:
     async def __aenter__(self):
         with trio.open_nursery() as nursery:
-            nursery.start_soon(my_startable)  # ASYNC113: 12
+            nursery.start_soon(my_startable)
+
+
+@asynccontextmanager
+async def yield_before_start_soon():
+    with trio.open_nursery() as bar:
+        yield
+        bar.start_soon(my_startable)
+
+
+# This was broken when visit_AsyncWith manually visited subnodes due to not
+# letting TypeTrackerVisitor interject.
+@asynccontextmanager
+async def nested():
+    with trio.open_nursery() as foo:
+        with trio.open_nursery() as bar:
+            bar.start_soon(my_startable)  # error: 12
+            yield