Relax future() and future_safe() argument types from Coroutine to Awaitable - #2480
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Both decorators typed their wrapped function argument as returning Coroutine, which rejects any callable typed as returning a plain Awaitable (e.g. an async def that awaits and returns another awaitable, rather than being annotated as returning a Coroutine itself), even though the runtime behavior only relies on awaiting the result. Widen the parameter type to Awaitable and drop the now unused _SecondType TypeVar. Fixes dry-python#2404
sobolevn
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Aug 4, 2026
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Related issues
Closes #2404
What changed
future()andfuture_safe()typed their wrapped function argument as returningCoroutine, which is stricter than needed. A callable typed asCallable[..., Awaitable[T]](for example anasync defthat awaits and returns some other awaitable, rather than one whose own return is annotatedCoroutine) failed type checking even though the decorators only everawaitthe result at runtime.This widens the parameter type on both decorators (and the internal
_future_safe_factoryhelper) toAwaitable, and removes the now unused_SecondTypeTypeVar that only existed to parameterizeCoroutine.Test plan
test_future_decorator.ymlandtest_future_safe_decorator.ymlcovering aCallable[[int], Awaitable[int]]argument that is not itself typed asCoroutine.pytest typesafety/test_future(53 passed)pytest tests -k future(133 passed)mypy returns(no issues)ruff check returns/future.py typesafety/test_future(all checks passed)