Chain dependencies between multiple promises

[roek5803]

Motivation: Why do you think this is important?

Right now to chain tasks which returns None within a workflow you can do that in multiple ways. One of the ways is with >>, though when doing it you can only chain 2 promises like: promise1 >> promise2, but you can not chain more promises like: promise1 >> promise2 >> promise3 then i get this error: TypeError: unsupported operand type(s) for >>: 'NoneType' and 'VoidPromise'.

Goal: What should the final outcome look like, ideally?

It would be good if you can use this syntax in order to chain multiple (more than 2) promises like this:

from time import sleep

from flytekit import task, workflow


@task
def task_a():
    sleep(4)
    print("task_a")


@task
def task_b():
    sleep(1)
    print("task_b")


@task
def task_c():
    print("task_c")


@workflow
def my_wf():
    promise1 = task_a()
    promise2 = task_b()
    promise3 = task_c()

    promise1 >> promise2 >> promise3


if __name__ == "__main__":
    my_wf()

Also this should be possible:

@workflow
def my_wf():
    task_a() >> task_b() >> task_c()

Describe alternatives you've considered

This is just an improvement of existing functionality.

Propose: Link/Inline OR Additional context

I didn't spend yo much time looking into how it should be fixed, but i guess it would be here: https://github.com/flyteorg/flytekit/blob/0bd3261c7567b0e25fa4cac88c883279b8752447/flytekit/core/promise.py#L350 where the function __rshift__ needs to return other promise

Are you sure this issue hasn't been raised already?

• Yes

Have you read the Code of Conduct?

• Yes

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