GCSToGCSOperator source_objects failing to parse xcom

[blaklaybul]

Apache Airflow Provider(s)

google

Versions of Apache Airflow Providers

10.15.0

Apache Airflow version

2.7.3

Operating System

debian

Deployment

Astronomer

Deployment details

Using astro runtime 9.15.0

What happened

The GCSToGCSOperator is throwing an error when trying to pass task output into the source_objects field.

 File "/usr/local/lib/python3.11/site-packages/airflow/providers/google/cloud/transfers/gcs_to_gcs.py", line 211, in __init__
    if source_objects and any(WILDCARD in obj for obj in source_objects):
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/airflow/models/xcom_arg.py", line 268, in __iter__
    raise TypeError("'XComArg' object is not iterable")

What you think should happen instead

This operator should be able to handle xcom, and we have no issue using the GCSToBigQueryOperator in the same way

How to reproduce

@task
def return_files():
    files = ['a','b','c','d']
    return files

files = return_files()

 extract_files = GCSToGCSOperator(
        task_id="fetch_data",
        source_bucket="source_bucket_name",
        source_objects=files,
        destination_bucket="dest_bucket_name",
        destination_object="foo",
        dag=dag,
    )

files >> extract_files

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[boring-cyborg[bot]]

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[potiuk]

You are not supposed to pass task results (which are dynamic) as initialization parameters in classic operator. This is not going to work - in classic operators the only way to get parameters dynamically resolved during execution is to use jinja templates.

If you want to pass the list, you need to pass it as jinja template where you pull parameters from xcom and use "render as native object". Or you can write what GCS to GCS operator does using hooks in taskflow-annotated task similarly to what is described in https://medium.com/apache-airflow/generic-airflow-transfers-made-easy-5fe8e5e7d2c2