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Sarj Code Standards

no-generic-json-parser

Parse consumed JSON fields with a bespoke declarative model instead of an open JSON parser.

SARJ552 Rule source Tests Catalog JSON

Why

An open JSON domain validates syntax and value kinds without declaring required fields or their relationships; consumers must then reconstruct the contract manually.

Fix

Declare only the fields the consumer needs in a named Pydantic model and use model_validate_json or model_validate. Allow unrelated fields when the wire contract permits them. Document an exact-code exception for genuinely schema-agnostic infrastructure.

Examples

Before — flagged An open JSON mapping does not declare the response fields
tests/test_api.py
from pydantic import JsonValue, RootModel




class Response(RootModel[dict[str, JsonValue]]):
    pass
After — preferred Declare just the field this consumer needs
tests/test_api.py
from pydantic import BaseModel




class Response(BaseModel):
    version: int