fix(providers/standard): remove premature param value validation in HITLOperator

[antonio-mello-ai]

Summary

Fixes a regression introduced when HITLOperator.validate_params() was extended to call self.params.validate(). HITL params are form fields filled by a human at runtime — validating their values at DAG parse time (__init__) causes ParamValidationError for any param that lacks an explicit default value, breaking DAG import.

Root cause: HITLOperator.__init__ → validate_params() → self.params.validate() → Param.resolve() raises ParamValidationError("No value passed and Param has no default value") if the param has no default. This validation runs at parse time, but no human input exists yet at that point.

Fix: Remove self.params.validate() from validate_params(). Value validation (type, schema, required fields) already happens correctly in validate_params_input() after the human submits the form.

The "_options" key check is preserved — it is a structural constraint that can and should be validated at init time.

Credit to @henry3260 who identified the same fix in #59653, which closed as stale without a review.

Before fixing

# DAG import fails with:
# ParamValidationError: Invalid input for param my_param: No value passed and Param has no default value
HITLOperator(
    task_id="ask_user",
    subject="Please provide input",
    options=["OK"],
    params={"my_param": Param(type="string")},  # no default — valid HITL use case
)

After fixing

# DAG imports successfully. Value is validated when the human submits the form.
HITLOperator(
    task_id="ask_user",
    subject="Please provide input",
    options=["OK"],
    params={"my_param": Param(type="string")},
)

Changes

• providers/standard/src/airflow/providers/standard/operators/hitl.py: removed self.params.validate() from validate_params(); added a docstring clarifying why value validation is intentionally deferred
• providers/standard/tests/unit/standard/operators/test_hitl.py:
  • Renamed test_validate_params parametrize to individual named tests for clarity
  • Removed the ParamValidationError case (wrong-type value at init) — this is no longer expected at init
  • Added test_param_without_default_does_not_raise_on_init — regression test for Regression: DAG import fails with HITLOperator when params have no explicit default (ParamValidationError) #59551
  • Added test_param_with_default_does_not_raise_on_init — happy path
  • Added test_param_with_wrong_value_type_does_not_raise_on_init — confirms value validation is deferred

Closes #59551

---

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In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in airflow-core/newsfragments.

Are there any user-facing changes?

Yes — DAGs using HITLOperator (or any subclass) with params that have no explicit default value will now import successfully, as they should.

Are there any breaking changes?

No. The removed call self.params.validate() was incorrect behavior — it caused ParamValidationError at DAG parse time. Removing it restores correct behavior without impacting any valid use case.

Commit message for squash merge:

fix(providers/standard): remove premature param value validation in HITLOperator

Generated with AI assistance: Implemented with Claude Code. The logic, root cause analysis, and test strategy were reviewed and confirmed correct.

[henry3260]

Thank you for taking this up！

[Shrividya]

Great fix, thanks for taking this on! The root cause explanation in the PR description is really clear.

[jason810496]

Thank you for the fix, LGTM overall.

[Lee-W]

overall looks good

[antonio-mello-ai]

Thanks for the review! All three items addressed:

1. Removed the newsfragment
2. Consolidated the three param validation tests into a single @pytest.mark.parametrize
3. Fixed docstring: DAG -> Dag