Once we added our own OpenAPI hook, it became easy to extend FastAPI's generation. The PinwheelPublicBaseModel.generate_examples() function is a custom method that finds the referenced Pydantic model in our codebase and produces a JSON example of that model.

pinwheel.app.py

import types

from fastapi import FastAPI

from pinwheel.openapi import custom_openapi

app = FastAPI()
app.openapi = types.MethodType(custom_openapi, app)

pinwheel.openapi.py

from typing import Dict

from fastapi import FastAPI
from fastapi.openapi.utils import get_openapi

from pinwheel.models import PinwheelPublicBaseModel

def add_examples_to_schema(openapi_schema: Dict) -> None:
    for path, verbs in openapi_schema["paths"].items():
        for verb, request in verbs.items():
            success_response = request["responses"]["200"]["content"]["application/json"]
            response_model_ref = success_response["schema"]["$ref"]
            success_response["examples"] = PinwheelPublicBaseModel.generate_examples(
                response_model_ref
            )

def custom_openapi(app: FastAPI, *args, **kwargs) -> Dict:
    """
    A custom wrapper around FastAPI's OpenAPI generator. 
    """
    openapi_schema = get_openapi(
        title="Pinwheel",
        description="Pinwheel is the API for Payroll",
        version="1.0.0",
        routes=app.routes
    )
    add_examples_to_schema(openapi_schema)
    app.openapi_schema = openapi_schema
    return app.openapi_schema