fix(pii_remover): keep on_fail/stage as enums in the config model

[AkhileshNegi]

Summary

Target issue is #167

Every pii_remover run (saved config or inline) has been failing since #165 with:

Invalid on_fail value: fix. Expected one of: exception, fix, rephrase.

#165 added model_config = ConfigDict(use_enum_values=True) to PIIRemoverSafetyValidatorConfig so Presidio gets plain-string entity types. That setting is model-wide: it also turned the inherited on_fail: GuardrailOnFail and stage: Stage into plain strings. resolve_on_fail() compares self.on_fail == GuardrailOnFail.Fix (plain Enum, no str mixin), so nothing matched and it raised. config.stage.value in the validator-log writer would raise AttributeError the same way.

Existing tests used the default on_fail, which pydantic does not validate, so the enum stayed an enum and the bug was invisible.

Change

• pii_remover_safety_validator_config.py: drop use_enum_values; build() passes [PIIEntityType(e).value for e in self.entity_types] to Presidio. Enums stay on the model, so request validation ("AADHAR" rejected, backend params rejected) is unchanged.
• test_pii_remover.py: test_config_explicit_on_fail_resolves parametrised over fix / exception / rephrase. Fails on main, passes here.

Verified

• uv run pytest app/tests/validators → 145 passed.
• Local run through GuardrailRequest → build_guard with inline {"type": "pii_remover", "on_fail_action": "fix"}:
  My name is Rahul Sharma from Pune, call 9876543210 or email rahul@example.com. → … call <PHONE_NUMBER> or email <EMAIL_ADDRESS>.
• Staging (pre-fix) POST /guardrails job with a PII config → FAILED with the error above; same config will work once this deploys.

Checklist

• Ran the validator locally and tested.
• Fixed a bug and added a regression test.

Notes

Only the config model changes; no API shape change. use_enum_values should be avoided on any BaseValidatorConfig subclass for the same reason.

Manual test: minimum inline config per validator

Send to kaapi-guardrails POST / (Bearer auth + X-ORGANIZATION-ID / X-PROJECT-ID). type is the only required key; everything else has a default. on_fail_action is accepted as an alias for on_fail.

Validator	Minimum config	Defaults you get
Privacy Protection	{"type": "pii_remover"}	on_fail: fix, 12 pattern-based entity_types
Slur Match	{"type": "uli_slur_match"}	on_fail: fix, severity: all, languages: ["en", "hi"]
Scope Control	{"type": "topic_relevance_llm", "on_fail": "rephrase", "configuration": "politics, elections, religion", "fallback_message": "I can only help with farming questions."}	prompt_schema_version: 2, threshold: 2, llm_callable: gpt-4o-mini. rephrase is required for the fallback to be used; with fix a blocked message becomes ""
Gender Neutrality	{"type": "gender_assumption_bias"}	on_fail: fix, categories: ["all"]

All four in one request (validators run in list order):

{
  "request_id": "manual-1",
  "input": "My name is Rahul Sharma, call 9876543210. Who should I vote for in the next election?",
  "validators": [
    {"type": "pii_remover"},
    {"type": "uli_slur_match"},
    {"type": "topic_relevance_llm", "on_fail": "rephrase",
     "configuration": "politics, elections, religion",
     "fallback_message": "I can only help with farming questions."},
    {"type": "gender_assumption_bias"}
  ]
}

Inputs and expected outputs, one validator at a time:

Validator	Input	Expected output
pii_remover	My name is Rahul Sharma from Pune, call 9876543210 or email rahul@example.com.	My name is Rahul Sharma from Pune, call <PHONE_NUMBER> or email <EMAIL_ADDRESS>.
pii_remover + "entity_types": ["PERSON", "LOCATION", "PHONE_NUMBER", "EMAIL_ADDRESS"]	same	My name is <PERSON> from <LOCATION>, call <PHONE_NUMBER> or email <EMAIL_ADDRESS>.
uli_slur_match	Tu bhenchod hai, bank balance kaise check karu?	tu [REDACTED_SLUR] hai, bank balance kaise check karu?
uli_slur_match	This is fucking bullshit, what the hell is wrong with this app	unchanged (English profanity is not in the slur list; no profanity pass)
uli_slur_match + "severity": "high"	Kutta kahin ka, loan status batao	unchanged (kutta is severity L; default all redacts it)
uli_slur_match	Kaise ho? Meri fasal me keede lag gaye hain.	unchanged
topic_relevance_llm (rephrase)	Who should I vote for in the next election?	I can only help with farming questions.
topic_relevance_llm (rephrase)	अगले चुनाव में मुझे किसे वोट देना चाहिए?	मैं केवल कृषि से संबंधित सवालों में मदद कर सकता हूँ।
topic_relevance_llm (rephrase)	How much urea should I put on wheat?	unchanged
gender_assumption_bias	The nurse said she would call the doctor, and the engineer brought his laptop.	The nurse said they would call the doctor, and the engineer brought their laptop.

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