update error descriptions in README to better reflect which errors work with which library, and minor updates. 102/103/104 now sees asyncio.exceptions.CancelledError as a critical exception. Fix import/arg detection of asyncio. add asyncio102_asyncio. add async103_all_imported. Finally make test_anyio_from_config autodetect the correct line number. Fix BASE_LIBRARY marker being interpreted as a bool. Make #NOTRIO/#NOASYNCIO/#NOANYIO run the visitor but ignore the result, instead of skipping, to check it doesn't crash. Generalize error-message-library-check.

Author: jakkdl

README.md

@@ -23,47 +23,47 @@ pip install flake8-async
 ```
 
 ## List of warnings
-
-- **ASYNC100**: A `with trio.fail_after(...):` or `with trio.move_on_after(...):`
+- **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.
-- **ASYNC101**: `yield` inside a 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` unless you use a shielded
-  cancel scope with a timeout.
-- **ASYNC103**: `except BaseException`, `except trio.Cancelled` 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` before.
-- **ASYNC104**: `Cancelled` and `BaseException` must be re-raised - when a user tries to `return` or `raise` a different exception.
-- **ASYNC105**: Calling a trio async function without immediately `await`ing it.
+- **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.
+- **ASYNC104**: `trio.Cancelled`/`anyio.get_cancelled_exc_class()`/`asyncio.exceptions.CancelledError`/`BaseException` must be re-raised. The same as ASYNC103, except specifically triggered on `return` or a different exception being raised.
+- **ASYNC105**: Calling a trio async function without immediately `await`ing it. This is only supported with trio functions, but you can get similar functionality with a type-checker.
 - **ASYNC106**: `trio`/`anyio`/`asyncio` must be imported with `import trio`/`import anyio`/`import asyncio` for the linter to work.
-- **ASYNC109**: Async function definition with a `timeout` parameter - use `trio.[fail/move_on]_[after/at]` instead
-- **ASYNC110**: `while <condition>: await trio.sleep()` should be replaced by a `trio.Event`.
+- **ASYNC109**: Async function definition with a `timeout` parameter - use `[trio/anyio].[fail/move_on]_[after/at]` instead.
+- **ASYNC110**: `while <condition>: await [trio/anyio].sleep()` should be replaced by a `[trio|anyio].Event`.
 - **ASYNC111**: Variable, from context manager opened inside nursery, passed to `start[_soon]` might be invalidly accessed while in use, due to context manager closing before the nursery. This is usually a bug, and nurseries should generally be the inner-most context manager.
 - **ASYNC112**: Nursery body with only a call to `nursery.start[_soon]` and not passing itself as a parameter can be replaced with a regular function call.
 - **ASYNC113**: Using `nursery.start_soon` in `__aenter__` doesn't wait for the task to begin. Consider replacing with `nursery.start`.
 - **ASYNC114**: Startable function (i.e. has a `task_status` keyword parameter) not in `--startable-in-context-manager` parameter list, please add it so ASYNC113 can catch errors when using it.
-- **ASYNC115**: Replace `trio.sleep(0)` with the more suggestive `trio.lowlevel.checkpoint()`.
-- **ASYNC116**: `trio.sleep()` with >24 hour interval should usually be `trio.sleep_forever()`.
+- **ASYNC115**: Replace `[trio|anyio].sleep(0)` with the more suggestive `[trio|anyio].lowlevel.checkpoint()`.
+- **ASYNC116**: `[trio|anyio].sleep()` with >24 hour interval should usually be `[trio|anyio].sleep_forever()`.
 - **ASYNC118**: Don't assign the value of `anyio.get_cancelled_exc_class()` to a variable, since that breaks linter checks and multi-backend programs.
 
 ### Warnings for blocking sync calls in async functions
-- **ASYNC200**: User-configured error for blocking sync calls in async functions. Does nothing by default, see [`trio200-blocking-calls`](#trio200-blocking-calls) for how to configure it.
-- **ASYNC210**: Sync HTTP call in async function, use `httpx.AsyncClient`.
+Note: 22X, 23X and 24X has not had asyncio-specific suggestions written.
+- **ASYNC200**: User-configured error for blocking sync calls in async functions. Does nothing by default, see [`async200-blocking-calls`](#async200-blocking-calls) for how to configure it.
+- **ASYNC210**: Sync HTTP call in async function, use `httpx.AsyncClient`. This and the other ASYNC21x checks look for usage of `urllib3` and `httpx.Client`, and recommend using `httpx.AsyncClient` as that's the largest http client supporting anyio/trio.
 - **ASYNC211**: Likely sync HTTP call in async function, use `httpx.AsyncClient`. Looks for `urllib3` method calls on pool objects, but only matching on the method signature and not the object.
 - **ASYNC212**: Blocking sync HTTP call on httpx object, use httpx.AsyncClient.
-- **ASYNC220**: Sync process call in async function, use `await nursery.start(trio.run_process, ...)`.
-- **ASYNC221**: Sync process call in async function, use `await trio.run_process(...)`.
-- **ASYNC222**: Sync `os.*` call in async function, wrap in `await trio.to_thread.run_sync()`.
-- **ASYNC230**: Sync IO call in async function, use `trio.open_file(...)`.
-- **ASYNC231**: Sync IO call in async function, use `trio.wrap_file(...)`.
-- **ASYNC232**: Blocking sync call on file object, wrap the file object in `trio.wrap_file()` to get an async file object.
-- **ASYNC240**: Avoid using `os.path` in async functions, prefer using `trio.Path` objects.
+- **ASYNC220**: Sync process call in async function, use `await nursery.start([trio|anyio].run_process, ...)`.
+- **ASYNC221**: Sync process call in async function, use `await [trio|anyio].run_process(...)`.
+- **ASYNC222**: Sync `os.*` call in async function, wrap in `await [trio|anyio].to_thread.run_sync()`.
+- **ASYNC230**: Sync IO call in async function, use `[trio|anyio].open_file(...)`.
+- **ASYNC231**: Sync IO call in async function, use `[trio|anyio].wrap_file(...)`.
+- **ASYNC232**: Blocking sync call on file object, wrap the file object in `[trio|anyio].wrap_file()` to get an async file object.
+- **ASYNC240**: Avoid using `os.path` in async functions, prefer using `[trio|anyio].Path` objects.
 
 ### Warnings disabled by default
-- **ASYNC900**: Async generator without `@asynccontextmanager` not allowed.
-- **ASYNC910**: Exit or `return` from async function with no guaranteed checkpoint or exception since function definition.
+- **ASYNC900**: Async generator without `@asynccontextmanager` not allowed. You might want to enable this on a codebase since async generators are inherently unsafe and cleanup logic might not be performed. See https://github.com/python-trio/flake8-async/issues/211 and https://discuss.python.org/t/using-exceptiongroup-at-anthropic-experience-report/20888/6 for discussion.
+- **ASYNC910**: Exit or `return` from async function with no guaranteed checkpoint or exception since function definition. You might want to enable this on a codebase to make it easier to reason about checkpoints, and make the logic of ASYNC911 correct.
 - **ASYNC911**: Exit, `yield` or `return` from async iterable with no guaranteed checkpoint since possible function entry (yield or function definition)
   Checkpoints are `await`, `async for`, and `async with` (on one of enter/exit).
 
 ### Removed Warnings
+- **TRIOxxx**: All error codes are now renamed ASYNCxxx
 - **TRIO107**: Renamed to TRIO910
 - **TRIO108**: Renamed to TRIO911
 - **TRIO117**: Don't raise or catch `trio.[NonBase]MultiError`, prefer `[exceptiongroup.]BaseExceptionGroup`. `MultiError` was removed in trio==0.24.0.

flake8_async/visitors/helpers.py

@@ -237,6 +237,9 @@ def has_exception(node: ast.expr) -> str | None:
             "trio.Cancelled",
             "anyio.get_cancelled_exc_class()",
             "get_cancelled_exc_class()",
+            "asyncio.exceptions.CancelledError",
+            "exceptions.CancelledError",
+            "CancelledError",
         ):
             return name
         return None

flake8_async/visitors/visitor103_104.py

@@ -22,8 +22,30 @@
 _suggestion_dict: dict[tuple[str, ...], str] = {
     ("anyio",): "anyio.get_cancelled_exc_class()",
     ("trio",): "trio.Cancelled",
+    ("asyncio",): "asyncio.exceptions.CancelledError",
 }
-_suggestion_dict[("anyio", "trio")] = "[" + "|".join(_suggestion_dict.values()) + "]"
+# TODO: ugly
+for a, b in (("anyio", "trio"), ("anyio", "asyncio"), ("asyncio", "trio")):
+    _suggestion_dict[(a, b)] = (
+        "[" + "|".join((_suggestion_dict[(a,)], _suggestion_dict[(b,)])) + "]"
+    )
+_suggestion_dict[
+    (
+        "anyio",
+        "asyncio",
+        "trio",
+    )
+] = (
+    "["
+    + "|".join(
+        (
+            _suggestion_dict[("anyio",)],
+            _suggestion_dict[("asyncio",)],
+            _suggestion_dict[("trio",)],
+        )
+    )
+    + "]"
+)
 
 _error_codes = {
     "ASYNC103": _async103_common_msg,
@@ -56,6 +78,7 @@ def visit_ExceptHandler(self, node: ast.ExceptHandler):
         marker = critical_except(node)
 
         if marker is None:
+            # not a critical exception handler
             return
 
         # If previous excepts have handled trio.Cancelled, don't do anything - namely
@@ -69,14 +92,21 @@ def visit_ExceptHandler(self, node: ast.ExceptHandler):
         ):
             error_code = "ASYNC103"
             self.cancelled_caught.add("anyio")
+        elif marker.name in (
+            "asyncio.exceptions.CancelledError",
+            "exceptions.CancelledError",
+            "CancelledError",
+        ):
+            error_code = "ASYNC103"
+            self.cancelled_caught.add("asyncio")
         else:
             if self.cancelled_caught:
                 return
             if len(self.library) < 2:
                 error_code = f"ASYNC103_{self.library_str}"
             else:
                 error_code = f"ASYNC103_{'_'.join(sorted(self.library))}"
-            self.cancelled_caught.update("trio", "anyio")
+            self.cancelled_caught.update("trio", "anyio", "asyncio")
 
         # Don't save the state of cancelled_caught, that's handled in Try and would
         # reset it between each except

flake8_async/visitors/visitor91x.py

@@ -93,6 +93,9 @@ def copy(self):
 
 
 def checkpoint_statement(library: str) -> cst.SimpleStatementLine:
+    # logic before this should stop code from wanting to insert the non-existing
+    # asyncio.lowlevel.checkpoint
+    assert library != "asyncio"
     return cst.SimpleStatementLine(
         [cst.Expr(cst.parse_expression(f"await {library}.lowlevel.checkpoint()"))]
     )
@@ -111,6 +114,7 @@ def __init__(self):
         self.noautofix: bool = False
         self.add_statement: cst.SimpleStatementLine | None = None
 
+        # used for inserting import if there's none
         self.explicitly_imported_library: dict[str, bool] = {
             "trio": False,
             "anyio": False,
@@ -250,8 +254,12 @@ def __init__(self, *args: Any, **kwargs: Any):
         self.try_state = TryState()
 
     def should_autofix(self, node: cst.CSTNode, code: str | None = None) -> bool:
-        return not self.noautofix and super().should_autofix(
-            node, "ASYNC911" if self.has_yield else "ASYNC910"
+        return (
+            not self.noautofix
+            and super().should_autofix(
+                node, "ASYNC911" if self.has_yield else "ASYNC910"
+            )
+            and self.library != ("asyncio",)
         )
 
     def checkpoint_statement(self) -> cst.SimpleStatementLine:
@@ -359,7 +367,9 @@ def leave_Return(
     ) -> cst.Return:
         if not self.async_function:
             return updated_node
-        if self.check_function_exit(original_node):
+        if self.check_function_exit(original_node) and self.should_autofix(
+            original_node
+        ):
             self.add_statement = self.checkpoint_statement()
         # avoid duplicate error messages
         self.uncheckpointed_statements = set()

flake8_async/visitors/visitor_utility.py

@@ -136,11 +136,17 @@ def __init__(self, *args: Any, **kwargs: Any):
         # see imports
         if self.options.anyio:
             self.add_library("anyio")
+        if self.options.asyncio:
+            self.add_library("asyncio")
 
     def visit_Import(self, node: cst.Import):
         for alias in node.names:
             if m.matches(
-                alias, m.ImportAlias(name=m.Name("trio") | m.Name("anyio"), asname=None)
+                alias,
+                m.ImportAlias(
+                    name=m.Name("trio") | m.Name("anyio") | m.Name("asyncio"),
+                    asname=None,
+                ),
             ):
                 assert isinstance(alias.name.value, str)
                 self.add_library(alias.name.value)

tests/eval_files/anyio_trio.py

@@ -2,6 +2,7 @@
 # ARG --enable=ASYNC220
 # NOTRIO
 # NOASYNCIO
+# set base library so trio doesn't get replaced when running with anyio
 # BASE_LIBRARY anyio
 
 # anyio eval will automatically prepend this test with `--anyio`

tests/eval_files/async102.py

@@ -1,5 +1,6 @@
 # type: ignore
 # NOASYNCIO
+# asyncio has different mechanisms for shielded scopes, so would raise additional errors in this file.
 from contextlib import asynccontextmanager
 
 import trio

tests/eval_files/async102_anyio.py

@@ -1,9 +1,12 @@
 # type: ignore
+# NOTRIO
+# NOASYNCIO
+# BASE_LIBRARY anyio
+# this test will raise the same errors with trio/asyncio, despite [trio|asyncio].get_cancelled_exc_class not existing
+# marked not to run the tests though as error messages will only refer to anyio
 import anyio
 from anyio import get_cancelled_exc_class
 
-# this one is fine to also run with trio
-
 
 async def foo(): ...
 

tests/eval_files/async102_asyncio.py

@@ -0,0 +1,39 @@
+# type: ignore
+# NOANYIO
+# NOTRIO
+# BASE_LIBRARY asyncio
+from contextlib import asynccontextmanager
+
+import asyncio
+
+
+async def foo():
+    # asyncio.move_on_after does not exist, so this will raise an error
+    try:
+        ...
+    finally:
+        with asyncio.move_on_after(deadline=30) as s:
+            s.shield = True
+            await foo()  # error: 12, Statement("try/finally", lineno-5)
+
+    try:
+        pass
+    finally:
+        await foo()  # error: 8, Statement("try/finally", lineno-3)
+
+    # asyncio.CancelScope does not exist, so this will raise an error
+    try:
+        pass
+    finally:
+        with asyncio.CancelScope(deadline=30, shield=True):
+            await foo()  # error: 12, Statement("try/finally", lineno-4)
+
+    # TODO: I think this is the asyncio-equivalent, but functionality to ignore the error
+    # has not been implemented
+
+    try:
+        ...
+    finally:
+        await asyncio.shield(  # error: 8, Statement("try/finally", lineno-3)
+            asyncio.wait_for(foo())
+        )

tests/eval_files/async103_all_imported.py

@@ -0,0 +1,79 @@
+# NOASYNCIO
+# NOANYIO - don't run it with substitutions
+import anyio
+import trio
+import asyncio
+from asyncio.exceptions import CancelledError
+from asyncio import exceptions
+
+try:
+    ...
+except trio.Cancelled:  # ASYNC103: 7, "trio.Cancelled"
+    ...
+except (
+    anyio.get_cancelled_exc_class()  # ASYNC103: 4, "anyio.get_cancelled_exc_class()"
+):
+    ...
+except CancelledError:  # ASYNC103: 7, "CancelledError"
+    ...
+except:  # safe
+    ...
+
+# reordered
+try:
+    ...
+except (
+    asyncio.exceptions.CancelledError  # ASYNC103: 4, "asyncio.exceptions.CancelledError"
+):
+    ...
+except (
+    anyio.get_cancelled_exc_class()  # ASYNC103: 4, "anyio.get_cancelled_exc_class()"
+):
+    ...
+except trio.Cancelled:  # ASYNC103: 7, "trio.Cancelled"
+    ...
+except:  # safe
+    ...
+
+# asyncio supports all three ways of importing asyncio.exceptions.CancelledError
+try:
+    ...
+except exceptions.CancelledError:  # ASYNC103: 7, "exceptions.CancelledError"
+    ...
+
+# catching any one of the exceptions in multi-library files will suppress errors on the bare except. It's unlikely a try block contains code that can raise multiple ones.
+try:
+    ...
+except (
+    anyio.get_cancelled_exc_class()  # ASYNC103: 4, "anyio.get_cancelled_exc_class()"
+):
+    ...
+except:  # safe ?
+    ...
+
+try:
+    ...
+except trio.Cancelled:  # ASYNC103: 7, "trio.Cancelled"
+    ...
+except:  # safe ?
+    ...
+
+try:
+    ...
+except (
+    asyncio.exceptions.CancelledError  # ASYNC103: 4, "asyncio.exceptions.CancelledError"
+):
+    ...
+except:  # safe ?
+    ...
+
+# Check we get the proper suggestion when all are imported
+try:
+    ...
+except BaseException:  # ASYNC103_anyio_asyncio_trio: 7, "BaseException"
+    ...
+
+try:
+    ...
+except:  # ASYNC103_anyio_asyncio_trio: 0, "bare except"
+    ...

tests/eval_files/async118.py

@@ -1,4 +1,7 @@
+# NOTRIO
+# NOASYNCIO
 # This raises the same errors on trio/asyncio, which is a bit silly, but inconsequential
+# marked not to run the tests though as error messages will only refer to anyio
 from typing import Any
 
 import anyio

tests/test_config_and_args.py

@@ -174,13 +174,24 @@ def test_anyio_from_config(tmp_path: Path, capsys: pytest.CaptureFixture[str]):
         "subprocess.Popen",
         "[anyio|trio]",
     )
-    err_file = str(Path(__file__).parent / "eval_files" / "anyio_trio.py")
-    expected = f"{err_file}:12:5: ASYNC220 {err_msg}\n"
+    err_file = Path(__file__).parent / "eval_files" / "anyio_trio.py"
+
+    # find the line with the expected error
+    for i, line in enumerate(err_file.read_text().split("\n")):
+        if "# ASYNC220: " in line:
+            # line numbers start at 1, enumerate starts at 0
+            lineno = i + 1
+            break
+    else:
+        raise AssertionError("could not find error in file")
+
+    # construct the full error message
+    expected = f"{err_file}:{lineno}:5: ASYNC220 {err_msg}\n"
     from flake8.main.cli import main
 
     returnvalue = main(
         argv=[
-            err_file,
+            str(err_file),
             "--config",
             str(tmp_path / ".flake8"),
         ]