Bug: StrEnum values in task function arguments get converted to strings, breaking method access

[leoperegrino]

Apache Airflow version

Other Airflow 2 version (please specify below)

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

apache/airflow:2.8.1-python3.11

What happened?

I'm running apache/airflow:2.8.1-python3.11 container and working with Enum and StrEnum to help me with the type system. The main difference between these two enum types is that StrEnum when cast to string (f'{MyStrEnum.A}' or str(MyStrEnum.A)) will auto use the .value attribute.

When passing a StrEnum to a tasks decorated function, StrEnum arguments will be cast to string. Calls to StrEnum methods then raise AttributeError. Normal enums work as usual.

What you think should happen instead?

The StrEnum argument should maintain its enum type when passed to the task, just like the regular Enum does. The task function signature indicates that the parameter should be a MyStrEnum instance, not a string.
While StrEnum is designed to automatically convert to string during string operations, this auto-conversion should not happen during parameter passing.

How to reproduce

from enum import Enum
from enum import StrEnum

from airflow.decorators import dag
from airflow.decorators import task


class MyEnum(Enum):
    A = 'A'


class MyStrEnum(StrEnum):
    A = 'A'


@dag(schedule_interval=None)
def enum_dag():

    @task(task_id='test_enum')
    def test_enum(enum: MyEnum):
        return enum.name

    @task(task_id='test_str_enum')
    def test_str_enum(str_enum: MyStrEnum):
        return str_enum.name

    test_enum(enum=MyEnum.A)
    test_str_enum(str_enum=MyStrEnum.A)


enum_dag()

Operating System

Amazon Linux 2023

Versions of Apache Airflow Providers

No response

Deployment

Docker-Compose

Deployment details

No response

Anything else?

test_enum

f063d55d4244
*** Found local files:
***   * /opt/airflow/logs/dag_id=enum_dag/run_id=manual__2025-02-11T16:58:48.370587+00:00/task_id=test_enum/attempt=1.log
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1956} INFO - Dependencies all met for dep_context=non-requeueable deps ti=<TaskInstance: enum_dag.test_enum manual__2025-02-11T16:58:48.370587+00:00 [queued]>
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1956} INFO - Dependencies all met for dep_context=requeueable deps ti=<TaskInstance: enum_dag.test_enum manual__2025-02-11T16:58:48.370587+00:00 [queued]>
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2170} INFO - Starting attempt 1 of 1
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2191} INFO - Executing <Task(_PythonDecoratedOperator): test_enum> on 2025-02-11 16:58:48.370587+00:00
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:60} INFO - Started process 2879665 to run task
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:87} INFO - Running: ['***', 'tasks', 'run', 'enum_dag', 'test_enum', 'manual__2025-02-11T16:58:48.370587+00:00', '--job-id', '6650', '--raw', '--subdir', 'DAGS_FOLDER/enum_dag.py', '--cfg-path', '/tmp/tmppaapxvvf']
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:88} INFO - Job 6650: Subtask test_enum
[2025-02-11, 16:58:50 UTC] {task_command.py:423} INFO - Running <TaskInstance: enum_dag.test_enum manual__2025-02-11T16:58:48.370587+00:00 [running]> on host f063d55d4244
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2480} INFO - Exporting env vars: AIRFLOW_CTX_DAG_OWNER='***' AIRFLOW_CTX_DAG_ID='enum_dag' AIRFLOW_CTX_TASK_ID='test_enum' AIRFLOW_CTX_EXECUTION_DATE='2025-02-11T16:58:48.370587+00:00' AIRFLOW_CTX_TRY_NUMBER='1' AIRFLOW_CTX_DAG_RUN_ID='manual__2025-02-11T16:58:48.370587+00:00'
[2025-02-11, 16:58:50 UTC] {python.py:201} INFO - Done. Returned value was: A
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1138} INFO - Marking task as SUCCESS. dag_id=enum_dag, task_id=test_enum, execution_date=20250211T165848, start_date=20250211T165850, end_date=20250211T165850
[2025-02-11, 16:58:50 UTC] {local_task_job_runner.py:234} INFO - Task exited with return code 0
[2025-02-11, 16:58:50 UTC] {taskinstance.py:3280} INFO - 0 downstream tasks scheduled from follow-on schedule check

test_str_enum

f063d55d4244
*** Found local files:
***   * /opt/airflow/logs/dag_id=enum_dag/run_id=manual__2025-02-11T16:58:48.370587+00:00/task_id=test_str_enum/attempt=1.log
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1956} INFO - Dependencies all met for dep_context=non-requeueable deps ti=<TaskInstance: enum_dag.test_str_enum manual__2025-02-11T16:58:48.370587+00:00 [queued]>
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1956} INFO - Dependencies all met for dep_context=requeueable deps ti=<TaskInstance: enum_dag.test_str_enum manual__2025-02-11T16:58:48.370587+00:00 [queued]>
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2170} INFO - Starting attempt 1 of 1
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2191} INFO - Executing <Task(_PythonDecoratedOperator): test_str_enum> on 2025-02-11 16:58:48.370587+00:00
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:60} INFO - Started process 2879664 to run task
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:87} INFO - Running: ['***', 'tasks', 'run', 'enum_dag', 'test_str_enum', 'manual__2025-02-11T16:58:48.370587+00:00', '--job-id', '6649', '--raw', '--subdir', 'DAGS_FOLDER/enum_dag.py', '--cfg-path', '/tmp/tmp5lou4idb']
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:88} INFO - Job 6649: Subtask test_str_enum
[2025-02-11, 16:58:50 UTC] {task_command.py:423} INFO - Running <TaskInstance: enum_dag.test_str_enum manual__2025-02-11T16:58:48.370587+00:00 [running]> on host f063d55d4244
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2480} INFO - Exporting env vars: AIRFLOW_CTX_DAG_OWNER='***' AIRFLOW_CTX_DAG_ID='enum_dag' AIRFLOW_CTX_TASK_ID='test_str_enum' AIRFLOW_CTX_EXECUTION_DATE='2025-02-11T16:58:48.370587+00:00' AIRFLOW_CTX_TRY_NUMBER='1' AIRFLOW_CTX_DAG_RUN_ID='manual__2025-02-11T16:58:48.370587+00:00'
[2025-02-11, 16:58:50 UTC] {taskinstance.py:2698} ERROR - Task failed with exception
Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.11/site-packages/airflow/models/taskinstance.py", line 433, in _execute_task
    result = execute_callable(context=context, **execute_callable_kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.11/site-packages/airflow/decorators/base.py", line 241, in execute
    return_value = super().execute(context)
                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.11/site-packages/airflow/operators/python.py", line 199, in execute
    return_value = self.execute_callable()
                   ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/airflow/.local/lib/python3.11/site-packages/airflow/operators/python.py", line 216, in execute_callable
    return self.python_callable(*self.op_args, **self.op_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/airflow/dags/enum_dag.py", line 27, in test_str_enum
    return str_enum.name
           ^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'name'
[2025-02-11, 16:58:50 UTC] {taskinstance.py:1138} INFO - Marking task as FAILED. dag_id=enum_dag, task_id=test_str_enum, execution_date=20250211T165848, start_date=20250211T165850, end_date=20250211T165850
[2025-02-11, 16:58:50 UTC] {standard_task_runner.py:107} ERROR - Failed to execute job 6649 for task test_str_enum ('str' object has no attribute 'name'; 2879664)
[2025-02-11, 16:58:50 UTC] {local_task_job_runner.py:234} INFO - Task exited with return code 1
[2025-02-11, 16:58:50 UTC] {taskinstance.py:3280} INFO - 0 downstream tasks scheduled from follow-on schedule check

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[boring-cyborg[bot]]

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[potiuk]

StrEnum is not supported for Python < 3.11. I doubt we want to add conditional code for Python 3.9 and 3.10 to handle StrEnums and Airflow is 3.9+ currently. I will convert it to a discussion - if more discussion is needed.