Prefect Tasks do not seem to cache when invoked in a map

Hi,

Trying to get the Prefect cache to work for a mapped task. It seems like the tasks are correctly cached, but something about the function signature prevents the cache from correctly being recalled. New to prefect, so definitely may just be operator error…

from prefect import Flow, task
from prefect.schedules import IntervalSchedule
import pendulum
from prefect.engine.cache_validators import all_inputs
import time

# Define flow run frequency
refresh_schedule = IntervalSchedule(
    start_date=pendulum.parse("2019-01-01"),
    interval=pendulum.duration(minutes=1)
)



@task
def a():
    return [1,2]

@task(
    cache_for=pendulum.duration(hours=1),
    cache_validator=all_inputs)
def b(a):
    time.sleep(2.5)
    
    

with Flow("test_flow", schedule=refresh_schedule) as test_flow:
    z = a()
    b.map(a=z)


test_flow.run()

[jeremiahpslewis]

Just read your PR, was curious to see what changes you needed to make. As part of going through the code, I saw a couple of changes that might improve readability / take advantage of the any short-circuiting in python. Please let me know what you think. 😃 https://github.com/PrefectHQ/prefect/pull/1072

[jeremiahpslewis]

Great! Looking forward to a fix, love the lib. And thanks for the quick response!! 😄