ASYNC002warningPro

blocking-in-async

Blocking calls in async functions defeat the purpose of async

Applies to: Go, JavaScript, Python, Rust, TypeScript

Why this matters

Async functions are meant to not block while waiting for I/O. If you use blocking calls like time.sleep() or requests.get() inside async code, you block the entire event loop and defeat the purpose of using async.

Catch it before it ships

pip install stablestack # or: npx stablestackstablestack # scans your project, ASYNC002 includedstablestack explain ASYNC002

ASYNC002 is part of the Pro rule set. See pricing — the free tier ships 24 checks with no signup.

False positive in your codebase? Suppress a single line with # noqa: ASYNC002

More Async Safety checks

ASYNC001

missing-await

Calling an async function without await returns a coroutine, not the result

ASYNC003

fire-and-forget-task

Fire-and-forget tasks hide errors and can cause silent failures

ASYNC004

silent-catch

Promise catch handler only logs - errors silently swallowed