#3887 [BUG] `map_task` with `partial` and `List` inputs error message Issue created by constanceferragu Describe the bug When running

map_task

with

partial

and fixed

List

inputs, the error message

ValueError: Map tasks do not support partial tasks with lists as inputs.

does not appear when the

List

input is the output of a previous task. Flyte does not recognise that the output of a task is a

List

here. This is linked to #3884. Expected behavior This error message should always appear when a

List

is input, otherwise it can be very difficult to debug. In some cases, the function will run with no error but the output will be wrong. Additional context to reproduce

@task 
def get_x() -> List[float]:
    return [1.0, 2.4, 3.9]
@task
def t1(x: List[float], y: float) -> List[float]:
    return x + [y]

@workflow
def wf(y: List[float]) -> List[List[float]]:
   x = get_x()
   partial_t1 = partial(t1, x=x)
   return map_task(partial_t1)(y=y)

When running

wf(y=[0.1, 0.3, 0.5, 0.7, 0.9])

,

t1

will be mapped according to

x=[1.0, 2.4, 3.9]

. Three map tasks will run, one for each value in

x

. The output will be

[1.0, 2.4, 3.9, 0.3], 
       [1.0, 2.4, 3.9, 0.5]]

instead of

[1.0, 2.4, 3.9, 0.3], 
       [1.0, 2.4, 3.9, 0.5], 
       [1.0, 2.4, 3.9, 0.7],  
       [1.0, 2.4, 3.9, 0.9]]

No error message will be thrown. Screenshots No response Are you sure this issue hasn't been raised already? ☑︎ Yes Have you read the Code of Conduct? ☑︎ Yes flyteorg/flyte