[BUG] MessagePack Decoder Fails to Deserialize Union with more than two non-None variants

[mao3267]

Describe the bug

Mentioned in flyteorg/flytekit#2859, while using dataclasses with union properties that have more than two non-None variants, the msgpack decoder will fail to decode the binary back to dataclass. Currently, I have raised an issue at Fatal1ty/mashumaro#255 describing this problem.

from dataclasses import dataclass
from flytekit import task
from flytekit.types.file import FlyteFile
from typing import Union
from flytekit.image_spec import ImageSpec


flytekit_hash = "d4171c3cd79ed406988d4213e4e79ee2b0bd2a93"
flytekit = f"git+https://github.com/mao3267/flytekit.git@{flytekit_hash}"

image_spec = ImageSpec(
    name="serialize-union-1",
    packages=[flytekit],
    builder="default",
    registry="localhost:30000",
    apt_packages=["git", "gh"],
)

@dataclass
class DC:
    ff: Union[None, int, FlyteFile]

@task(container_image=image_spec)
def t_dc() -> DC:
    return DC(ff="s3://path")

Expected behavior

The expected output should be something like DC(ff=/var/folders/nc/zmjfff853y33j17lwwdk299w0000gn/T/flyte-h8b6o6_w/sandbox/local_flytekit/9489edd65d6ce1b52fa248a4ba0ba6a4/path), where ff is a FlyteFile type.

Current Output: DC(ff={'path': 's3://path'}), where the ff is a dict.

Additional context to reproduce

No response

Screenshots

No response

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

• Yes

Have you read the Code of Conduct?

• Yes

[Future-Outlier]

this is fixed by mashumaro!

[eapolinario]

Can you add a unit test to show that this works?