matterrr opened a new issue, #37977:
URL: https://github.com/apache/airflow/issues/37977
### Apache Airflow version
2.8.2
### If "Other Airflow 2 version" selected, which one?
_No response_
### What happened?
The arg `include_prior_dates` in `TaskInstance.xcom_pull()` has the
following definition:
> :param include_prior_dates: If False, only XComs from the current
> execution_date are returned. If *True*, XComs from previous
dates
> are returned as well.
In practice, `xcom_pull(key="<some_key>", include_prior_dates=True)` only
returns a single xcom (the most recent prior DAG run) when only the `key` is
specified. I think it would only return multiple xcoms if multiple `task_ids`
are specified, or the xcom(s) was pushed from a mapped task.
### What you think should happen instead?
I think that the `include_prior_dates` being plural implies that
`xcom_pull(key="<some_key>", include_prior_dates=True)` _should_ return an
`array` of xcoms for all `dag_runs`. This is even consistent with the wording
in the `get_many()` function called in `xcom_pull()`:
> :param include_prior_dates: If *False* (default), only XComs from
the
> specified DAG run are returned. If *True*, all matching XComs
are
> returned regardless of the run it belongs to.
But strangely, the `get_one()` function in `BaseXCom` has this wording:
> :param include_prior_dates: If *False* (default), only XCom from
the
> specified DAG run is returned. If *True*, **the latest
matching XCom is
> returned regardless of the run it belongs to**.
At the least, the wording `include_prior_dates` should be changed to
`include_prior_date` (singular) if xcoms from _only_ the previous DAG run will
ever be returned.
### How to reproduce
h3. Example Code
```
import logging
import sys
from datetime import datetime
from airflow.decorators import dag, task
default_args = {
"owner": "airflow",
"depends_on_past": False,
"start_date": datetime(2021, 1, 1),
"retries": 0,
}
logger = logging.getLogger(__name__)
@dag(
dag_id="test.xcom",
default_args=default_args,
schedule=None,
)
def test_xcom():
@task()
def get_recent_xcom(**context):
from datetime import datetime
ti = context["ti"]
xcom_results = ti.xcom_pull(key="test_xcom",
include_prior_dates=True)
print(f"{xcom_results=}")
ti.xcom_push(key="test_xcom", value=f"{datetime.now()}")
get_recent_xcom()
test_xcom()
dag.doc_md = """This test DAG logs the xcom."""
```
h3. Steps
1. Run the DAG, noting the xcom value will be `None` for the first run
2. Run the DAG subsequent times, noting the `xcom_pull()` only ever returns
a single value from the previous DAG run
### Operating System
Debian GNU/Linux 11 (bullseye)
### Versions of Apache Airflow Providers
_No response_
### Deployment
Docker-Compose
### 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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