[BUG] None should not be allows as maptask output

[hamersaw]

Describe the bug

Using None as a maptask output can cause undefined behavior when executing, especially when used with min_success_ratio.

Expected behavior

None should probably not be allowed as a maptask output type. A comprehensive test to determine the correct behavior should be scoped here.

Additional context to reproduce

This workflow will fail:

@task
def hello_none(name: str) -> None:
    if name == "b":
        raise Exception("B is not allowed")

    return

@workflow
def test_hello():
    map_task(hello_none, min_success_ratio=0.1)(name=["a", "b", "c"])

whereas this workflow completes without any output values:

@task
def hello_none(name: str) -> None:
    return

@workflow
def test_hello():
    map_task(hello_none, min_success_ratio=0.1)(name=["a", "b", "c"])

Screenshots

No response

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

• Yes

Have you read the Code of Conduct?

• Yes

[pvditt]

This was not an issue with the ArrayNode implementation for maptasks. For some reason flyteorg/flytekit#2242 fixes it for legacy maptasks. Looked into for longer than I should've and couldn't quickly figure out why.