Dynamic Task Mapping Skips Before Upstream Has Started

[hoiekim]

Apache Airflow version

Other Airflow 2/3 version (please specify below)

If "Other Airflow 2/3 version" selected, which one?

3.0.6

What happened?

"Dynamic Task Mapping Skips Before Upstream Has Started"

This is a similar bug as https://github.com/apache/airflow/issues/28973

Difference is that adding "trigger_rule": TriggerRule.NONE_FAILED_MIN_ONE_SUCCESS makes the bug happens.

What you think should happen instead?

Should not skip tasks

How to reproduce

from datetime import datetime

from airflow import DAG
from airflow.operators.empty import EmptyOperator
from airflow.decorators import dag, task, task_group
from airflow.utils.trigger_rule import TriggerRule


@task
def get_the_list():
    return ["one", "two", "three"]


@task
def process_something(x: str, y: str, **kwargs):
    output = f"{x}_{y}"
    print(output)
    return output


@task_group
def the_task_group(x: str, y: str, **kwargs):
    start = EmptyOperator(task_id="start")

    something = process_something(x, y)
    another = process_something(something)

    end = EmptyOperator(task_id="end")

    start >> something >> another >> end


@dag(
    default_args={
        "start_date": datetime(year=2025, month=12, day=1),
        "trigger_rule": TriggerRule.NONE_FAILED_MIN_ONE_SUCCESS,
    }
)
def dtm_bug_reproduce_dag():
    start = EmptyOperator(task_id="start")
    end = EmptyOperator(task_id="end")

    the_list = get_the_list()

    mapped_group = (
        the_task_group
        .partial(x="base")
        .expand(y=the_list)
    )

    start >> the_list >> mapped_group >> end


dag = dtm_bug_reproduce_dag()

Operating System

MWAA

Versions of Apache Airflow Providers

No response

Deployment

Amazon (AWS) MWAA

Deployment details

No response

Anything else?

I was able to reproduce the bug with the attached snippet in 3.0.6. I haven't tried it in the latest version but I did search through the issues and haven't found it reported so I think it's likely that it's not yet fixed.

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

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