fix: nested non-DAG with-statement prematurely exits DAG context in version inflation checker

[kalluripradeep]

Closes #68796

What's the problem?

AirflowRuntimeVaryingValueChecker.visit_With() called exit_dag_context() unconditionally at the end of every with-statement. When a non-DAG with-statement (e.g. with open(...) as f) was nested inside a DAG with-block, it would reset is_in_dag_context=False. Any tasks constructed after the nested with — but still inside the DAG block — were invisible to the checker and never flagged for runtime-varying values even when they used datetime.now(), random(), etc.

with DAG('my_dag') as dag:
    with open('file.txt') as f:   # <-- this incorrectly exited DAG context
        data = f.read()
    # BUG: datetime.now() not flagged — checker thinks we're outside DAG
    t1 = BashOperator(task_id='t', bash_command=str(datetime.now()))

Root cause

# visit_With (before fix) — unconditional, wrong
self.dag_detector.exit_dag_context()

Fix

Guard the call with if is_with_dag_context so only the with-statement that actually entered the DAG context exits it.

if is_with_dag_context:
    self.dag_detector.exit_dag_context()

Changes

• airflow-core/src/airflow/utils/dag_version_inflation_checker.py — one-line guard
• airflow-core/tests/unit/utils/test_dag_version_inflation_checker.py — 4 regression tests