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Sarj Sarj Sarj Standards

require-pydantic-for-external-json

Proven external JSON record fields are consumed before runtime schema validation.

SARJ411 Rule source Tests Catalog JSON

Why

Annotations, casts, and partial key checks do not validate a wire protocol; a maintained runtime schema makes required fields, types, and protocol versions explicit at the boundary.

Fix

Validate raw JSON with Model.model_validate_json(...) or TypeAdapter(Model).validate_json(...); for an already-decoded response, use model_validate, validate_python, or another maintained runtime schema validator before reading fields.

Examples

Before — flagged External JSON read as a dictionary
protocol.py
import httpx




def fetch() -> object:
    report = httpx.get("https://api.example/report").json()
    return report.get("version")
After — preferred External JSON validated by a boundary model
protocol.py
import httpx
from pydantic import BaseModel




class Report(BaseModel):
    version: int




def fetch() -> Report:
    raw = httpx.get("https://api.example/report").json()
    report = Report.model_validate(raw)
    return report