Feature request: opt-in flag to require presence of declared optional properties

[dmb225]

Summary

I am wondering if we could add an opt-in flag (require_properties_presence or a shorter name) to also require presence of properties declared in properties (even if not in required)?

Default behavior should stay unchanged and spec-compliant.

Why this is useful

For contract/feature tests, we need to detect missing or accidental field removals inAPI responses.
Today, this requires custom recursive checks on top of openapi-schema-validator.

Environment

• openapi-schema-validator: 0.6.3
• jsonschema: 4.25.1
• Python: 3.12.3
• OpenAPI version used: 3.0.3
• OS: Ubuntu 24.04.2 LTS (Linux)

Minimal reproduction

from openapi_schema_validator import validate, OAS30Validator

schema = {
    "type": "object",
    "properties": {
        "id": {"type": "string"},
        "nickname": {"type": "string"},
    },
    "required": ["id"],
}
instance = {"id": "42"}  # nickname missing

validate(instance, schema, cls=OAS30Validator)  # currently valid

Observed

Validation succeeds because nickname is optional.

Expected (opt-in only)

With a new flag enabled, validation should fail and report missing declared properties.

Proposed API

Example:

validate(..., require_properties_presence=False)  # (default False)

Thanks for your time