mehmax opened a new issue #18840:
URL: https://github.com/apache/airflow/issues/18840
### Apache Airflow version
2.1.0
### Operating System
CentOs 7
### Versions of Apache Airflow Providers
_No response_
### Deployment
Other
### Deployment details
_No response_
### What happened
This example DAG
task 1 is assigned to task group 1 and pushes return_value to xcom
task 2 reads return_value of task 1 and echos it.
```
from datetime import datetime
from airflow import DAG
from airflow.operators.bash import BashOperator
from airflow.utils.task_group import TaskGroup
with DAG(dag_id='test_xcom', start_date=datetime(2021, 6, 1),
schedule_interval='@once') as dag:
with TaskGroup(group_id='group1') as g1:
t1 = BashOperator(
task_id='task1',
bash_command='echo abcde',
do_xcom_push=True
)
t2 = BashOperator(
task_id='task2',
bash_command='''echo {{ ti.xcom_pull(task_ids='task1') }}''',
dag=dag
)
g1 >> t2
```
The problem is, that `xcom_pull(task_ids='task1')` is always returning None
even though it was pushed correctly:
### What you expected to happen
Task 2 should be able to read xcom from task 1
### How to reproduce
Try this DAG:
```
from datetime import datetime
from airflow import DAG
from airflow.operators.bash import BashOperator
from airflow.utils.task_group import TaskGroup
with DAG(dag_id='test_xcom', start_date=datetime(2021, 6, 1),
schedule_interval='@once') as dag:
with TaskGroup(group_id='group1') as g1:
t1 = BashOperator(
task_id='task1',
bash_command='echo abcde',
do_xcom_push=True
)
t2 = BashOperator(
task_id='task2',
bash_command='''echo {{ ti.xcom_pull(task_ids='task1') }}''',
dag=dag
)
g1 >> t2
```
let it run and look into the logfile:
```
[2021-10-08 16:39:44,898] {subprocess.py:52} INFO - Tmp dir root location:
/tmp
[2021-10-08 16:39:44,899] {subprocess.py:63} INFO - Running command:
['bash', '-c', 'echo None']
[2021-10-08 16:39:44,906] {subprocess.py:75} INFO - Output:
[2021-10-08 16:39:44,907] {subprocess.py:79} INFO - None
[2021-10-08 16:39:44,907] {subprocess.py:83} INFO - Command exited with
return code 0
[2021-10-08 16:39:44,920] {taskinstance.py:1184} INFO - Marking task as
SUCCESS. dag_id=test_xcom, task_id=task2, execution_date=20211008T143942,
start_date=20211008T143944, end_date=20211008T143944
[2021-10-08 16:39:44,931] {taskinstance.py:1245} INFO - 0 downstream tasks
scheduled from follow-on schedule check
[2021-10-08 16:39:44,970] {local_task_job.py:151} INFO - Task exited with
return code 0
```
### Anything else
For checking if there was something else wrong, I tried the exact same DAG,
but without TaskGroup.
```
from datetime import datetime
from airflow import DAG
from airflow.operators.bash import BashOperator
with DAG(dag_id='test_xcom2', start_date=datetime(2021, 6, 1),
schedule_interval='@once') as dag:
t1 = BashOperator(
task_id='task1',
bash_command='echo abcde',
do_xcom_push=True
)
t2 = BashOperator(
task_id='task2',
bash_command='''echo {{ ti.xcom_pull(task_ids='task1') }}''',
dag=dag
)
t1 >> t2
```
With This DAG xcom_pull is working:
```
[2021-10-08 16:39:41,502] {subprocess.py:52} INFO - Tmp dir root location:
/tmp
[2021-10-08 16:39:41,502] {subprocess.py:63} INFO - Running command:
['bash', '-c', 'echo abcde']
[2021-10-08 16:39:41,514] {subprocess.py:75} INFO - Output:
[2021-10-08 16:39:41,514] {subprocess.py:79} INFO - abcde
[2021-10-08 16:39:41,514] {subprocess.py:83} INFO - Command exited with
return code 0
[2021-10-08 16:39:41,549] {taskinstance.py:1184} INFO - Marking task as
SUCCESS. dag_id=test_xcom2, task_id=task2, execution_date=20211008T143938,
start_date=20211008T143941, end_date=20211008T143941
[2021-10-08 16:39:41,561] {taskinstance.py:1245} INFO - 0 downstream tasks
scheduled from follow-on schedule check
[2021-10-08 16:39:41,589] {local_task_job.py:151} INFO - Task exited with
return code 0
```
### 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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