I have come across what appears to be a bug with partitioned assets. I have created an example completely devoid of any custom code. If you take this example and materialize the job with the date of 2023-03-02 it works, no problem. If you materialize the asset with it's first possible date of 2023-03-01 then the first asset's return value that is passed to the second asset (which should be a simple string) will in fact be a None and the second asset will blow up. I am on dagster 1.1.13.

from dagster import asset, define_asset_job, build_schedule_from_partitioned_job, DailyPartitionsDefinition

@asset(config_schema={},

partitions_def=DailyPartitionsDefinition(start_date='2023-03-01'))

def first_asset(context) -> str:

part_date_str = context.asset_partition_key_for_output()

return part_date_str + " This text came from first asset"

@asset(config_schema={},

partitions_def=DailyPartitionsDefinition(start_date='2023-03-01'))

def second_asset(context, first_asset) -> None:

part_date_str = context.asset_partition_key_for_output()

<http://context.log.info|context.log.info>("first asset returned: " + first_asset)

return None

example_job = define_asset_job("example_job", selection=["*second_asset"],

partitions_def=DailyPartitionsDefinition(start_date='2023-03-01'), config={})

example_schedule = build_schedule_from_partitioned_job(example_job,

name="Daily_Partitioned_Job_For_example_job",

minute_of_hour=15, hour_of_day=7)