MaiHoangViet1809 opened a new issue, #27952:
URL: https://github.com/apache/airflow/issues/27952
### Apache Airflow version
2.4.3
### What happened
when use output from task decorator as parameter (external_task_ids) in
ExternalTaskSensor, it show up this log:
Broken DAG: [*******/airflow/dags/TEST_NEW_PIPELINE.py] Traceback (most
recent call last):
File
"*******/env3.10.5/lib/python3.10/site-packages/airflow/models/baseoperator.py",
line 408, in apply_defaults
result = func(self, **kwargs, default_args=default_args)
File
"*******/env3.10.5/lib/python3.10/site-packages/airflow/sensors/external_task.py",
line 164, in __init__
if external_task_ids and len(external_task_ids) >
len(set(external_task_ids)):
TypeError: object of type 'PlainXComArg' has no len()
### What you think should happen instead
this document
https://airflow.apache.org/docs/apache-airflow/stable/tutorial/taskflow.html
show that we can use it without any warning, note about it.
I think need to fix the line in error log:
"if external_task_ids and len(external_task_ids) >
len(set(external_task_ids)):"
### How to reproduce
```
from airflow.decorators import dag, task
from airflow.operators.python import get_current_context
from airflow.sensors.external_task import ExternalTaskSensor
from datetime import datetime
configure = {"dag_id": "test_new_skeleton",
"schedule": None,
"start_date": datetime(2022,1,1),
}
@task
def preprocess_dependency() -> list:
return ["random-task-name"]
@dag(**configure)
def pipeline():
t_preprocess = preprocess_dependency()
task_dependency = ExternalTaskSensor(task_id=f"Check_Dependency",
external_dag_id='random-dag-name-that-exist',
external_task_ids=t_preprocess ,
poke_interval=60,
mode="reschedule",
timeout=172800,
allowed_states=['success'],
failed_states=['failed', 'skipped'],
check_existence=True,)
dag = pipeline()
```
### Operating System
REHL 7
### Versions of Apache Airflow Providers
_No response_
### Deployment
Virtualenv installation
### Deployment details
_No response_
### 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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