Hey all. I've been struggling recently with a type error from Pyright with my flows. I've just upgra...

Nash Taylor

12/17/2024, 3:45 AM

Hey all. I've been struggling recently with a type error from Pyright with my flows. I've just upgraded to Prefect 3.1.7. I'll thread the error I'm getting so they don't clutter. When I decorate a flow simply with

@flow

, everything is fine. When I try to add arguments, such as

@flow(task_runner=ThreadPoolTaskRunner(max_workers=3))

, I get the error in the thread. Thanks in advance for any help!

Nash Taylor

12/17/2024, 3:45 AM

Copy code

Argument of type "ThreadPoolTaskRunner" cannot be assigned to parameter "task_runner" of type "TaskRunner[PrefectFuture[R@flow]] | None" in function "flow"
  Type "ThreadPoolTaskRunner" is incompatible with type "TaskRunner[PrefectFuture[R@flow]] | None"
    "ThreadPoolTaskRunner" is incompatible with "TaskRunner[PrefectFuture[R@flow]]"
      Type parameter "F@TaskRunner" is invariant, but "PrefectConcurrentFuture[Unknown]" is not the same as "PrefectFuture[R@flow]"
    "ThreadPoolTaskRunner" is incompatible with "None"PylancereportArgumentType

Damien

12/18/2024, 9:32 AM

Might be related to this issue https://github.com/PrefectHQ/prefect/issues/16396

Joe

01/02/2025, 9:08 PM

I'm running into this problem as well. Looking at the source code, I see task_runner is of type None, which is very odd.

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