fix serialize_template_field handling callable value in dict

[wjddn279]

closed: #63334

Cause

The serialization result of the DAG is as follows.

{
  "__var": {
    "op_args": [],
    "task_id": "consume",
    "ui_color": "#ffefeb",
    "op_kwargs": "{'values': [3, 1, 2], 'sort_key': <function unstable_dag.<locals>.<lambda> at 0xf2dc11567e20>}",
    "task_type": "_PythonDecoratedOperator",
    "retry_delay": 300.0,
    "_task_module": "airflow.providers.standard.decorators.python",
    "_operator_name": "@task",
    "template_fields": [
      "templates_dict",
      "op_args",
      "op_kwargs"
    ],
    "_needs_expansion": false,
    "python_callable_name": "consume",
    "template_fields_renderers": {
      "op_args": "py",
      "op_kwargs": "py",
      "templates_dict": "json"
    }
  },

When serializing a dict containing lambda function definitions, the object's id value is reflected as-is, causing version changes on every serialization. The root cause is that when a dict contains callable objects, is_jsonable returns False, and since the dict itself is not callable, it falls through to that code path.

Solution

I added logic to filter out this case and convert callable objects consistently within the existing dict handling (sorting) logic. I have confirmed locally that this resolves the issue.

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[Copilot]

Pull request overview

Fixes non-deterministic DAG serialization when templated dict fields contain callable values (e.g., lambdas), preventing serialized output from changing on every run due to function object addresses.

Changes:

• Sanitizes callable values during recursive dict sorting in serialize_template_field.
• Refactors callable stringification into a helper for consistent formatting.
• Adds unit tests intended to validate stable serialization when dicts contain callables.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
airflow-core/src/airflow/serialization/helpers.py	Makes callable values in dicts serialize to a stable string during recursive sorting.
airflow-core/tests/unit/serialization/test_helpers.py	Adds regression tests around dicts containing callables to prevent unstable serialization.