Pre-commit config files using prek syntax contain extra fields like priority: 0 on hooks and minimum_prek_version at the top level. These are accepted by our pydantic models (extra="allow"), but _fancy_model_dump_base_model crashes because for key, value in model: yields extra fields while model.model_fields[key] only contains declared fields.

Fix

In _fancy_model_dump_base_model, use model_fields.get(key) instead of model_fields[key] and branch:

field_info = model.__class__.model_fields.get(key)
if field_info is not None:
    # declared field: check defaults, aliases, reference diffing
    ...
else:
    # extra field: always include, use raw key
    display_key = key

Tests

• Unit tests (TestExtraFields): extra field inclusion, interaction with defaults/references, nested models
• Integration tests: add_repo against YAML with priority, minimum_prek_version, and arbitrary extra keys at top-level/repo/hook levels, verified via parsed YAML structure