Added static check for conn-fields defined in provider.yaml

[dabla]

Added static check for conn-fields defined in provider.yaml to make sure those correspond with the ones defined in the get_connection_form_widgets method of the corresponding hook.

Add static check: validate conn-fields in provider.yaml against get_connection_form_widgets()

Background

Airflow's connection UI has two layers:

• Legacy Flask UI — driven by get_connection_form_widgets() on each Hook class.
• New React UI — driven by the conn-fields mapping in provider.yaml (and the generated get_provider_info.py).

An existing static check already works in one direction: if a field is declared in provider.yaml conn-fields but absent from get_connection_form_widgets(), it is automatically added to the hook.

What this PR adds

This PR adds the reverse check: fields declared in provider.yaml conn-fields must exist in the corresponding hook's get_connection_form_widgets().

In other words — conn-fields must be a valid subset of the hook's form widgets. It is intentionally not required to be an identical set: some Flask form fields may be deliberately omitted from the new React UI.

The check:

1. Imports the hook class referenced in each connection-types entry.
2. Skips the entry silently when the hook cannot be imported (optional provider dependencies), does not override get_connection_form_widgets(), or has no conn-fields declared (the new UI intentionally exposes no custom fields for that connection type).
3. Reports an error when a key present in conn-fields is not found in get_connection_form_widgets() — those are stale or mistyped field names that the React UI would try to render but the hook doesn't know about.

Error example

Mismatch between `conn-fields` in providers/my_provider/provider.yaml and
`airflow.providers.my_provider.hooks.my_hook.MyHook.get_connection_form_widgets()`
for connection-type 'my_conn_type':
  Fields in provider.yaml conn-fields but NOT in get_connection_form_widgets(): stale_field
How to fix it: Remove the stale key(s) from conn-fields in provider.yaml.

Files changed

File	Change
scripts/ci/prek/check_provider_conn_fields.py	New validation helpers (pure Python, no third-party deps, unit-testable outside Breeze)
scripts/in_container/run_provider_yaml_files_check.py	Wires the new check into the existing provider YAML validation run
scripts/tests/ci/prek/test_check_conn_fields_match_form_widgets.py	Unit tests covering all branches

---

Was generative AI tooling used to co-author this PR?

• [ x ] Yes (please specify the tool below)

Claude Sonnet 4.6 (GitHub Copilot CLI)

---

• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

[potiuk]

Thanks @dabla — nice, well-factored check: the pure helpers in check_provider_conn_fields.py are cleanly separated from the import glue and thoroughly unit-tested, and the subset semantics (React conn-fields ⊆ Flask form widgets) are the right call.

One thing worth flagging on process: the check-provider-yaml-valid prek hook only triggers on provider.yaml changes, so this PR's own CI never actually runs the new check against real providers — only the mocked unit tests ran here. I reproduced the real check locally against the full set of providers that declare conn-fields (installed all 33, ran _get_widget_keys + the subset comparison): 50 connection-type entries validated, 0 stale keys, so it passes cleanly against current main and won't start failing unrelated PRs. Approving on that basis. It might still be worth running prek run check-provider-yaml-valid --all-files once before merge as a belt-and-suspenders check in the full Breeze environment (a handful of hooks — AzureBatchHook etc. — I could only skip locally on optional-dep import errors).

Two non-blocking nits inline (docstring correctness + a coverage note). Neither blocks merge.

---

This review was drafted with AI assistance (Claude Code, Opus 4.8) and may contain mistakes; an Apache Airflow maintainer (@potiuk) has read and confirmed it before posting. For what the project considers a maintainer review, see the contributing guide.

Drafted-by: Claude Code (Opus 4.8); reviewed by @potiuk before posting

[github-actions]

Backport successfully created: v3-3-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-3-test