MatrixManAtYrService opened a new issue #21775:
URL: https://github.com/apache/airflow/issues/21775
### Apache Airflow version
2.2.4 (latest released)
### What happened
This DAG has a problem: star-expansion can't be used on XComArgs
```
from airflow import DAG
from airflow.decorators import task
from datetime import datetime
@task
def xcomify():
return [1, 2]
@task
def add(a, b):
return a + b
with DAG(dag_id="some_numbers", start_date=datetime(1970, 1, 1)) as the_dag:
add(*xcomify())
```
If you check it for errors like `python dags/the_dag.py` it'll just hang
without error output until interrupted.
If you include it in your dags folder, you'll get an error:
> Broken DAG: [/usr/local/airflow/dags/star_pos_expansion.py] Traceback
(most recent call last):
> File
"/usr/local/lib/python3.9/site-packages/airflow/models/xcom_arg.py", line 63,
in __init__
> def __init__(self, operator: BaseOperator, key: str = XCOM_RETURN_KEY):
> File "/usr/local/lib/python3.9/site-packages/airflow/utils/timeout.py",
line 37, in handle_timeout
> raise AirflowTaskTimeout(self.error_message)
> airflow.exceptions.AirflowTaskTimeout: DagBag import timeout for
/usr/local/airflow/dags/star_pos_expansion.py after 30.0s.
> Please take a look at these docs to improve your DAG import time:
> *
http://apache-airflow-docs.s3-website.eu-central-1.amazonaws.com/docs/apache-airflow/latest/best-practices.html#top-level-python-code
> *
http://apache-airflow-docs.s3-website.eu-central-1.amazonaws.com/docs/apache-airflow/latest/best-practices.html#reducing-dag-complexity,
PID: 169
### What you expected to happen
A more specific error, and faster. Something that warns that XComArgs can't
be expanded as if they were lists (which they might reference, but which is not
known by Airflow at dag-parse time).
### How to reproduce
Run a python file containing the dag above. Notice that it runs forever
without error.
Add it to your dags list. Notice that you get a timeout error instead of
something useful.
### Operating System
docker/debian
### Versions of Apache Airflow Providers
N/A
### Deployment
Astronomer
### Deployment details
`astro dev start`
Dockerfile:
```
FROM quay.io/astronomer/ap-airflow:2.2.4-onbuild
```
### Anything else
_No response_
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [X] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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