FastAPI throws TypeError: Object of type 'type' is not JSON serializable error on creating openapi.json when using a BaseModel which includes Field and a constr object as default.
A MRE:
from fastapi import FastAPI
from pydantic import BaseModel, Field, constr
app = FastAPI()
class CoolModel(BaseModel):
this: str = Field(constr(strip_whitespace=True), min_length=10, max_length=20)
@app.get("/", response_model=CoolModel)
async def something(some_model: CoolModel):
return some_model
Going to http://localhost:8000/openapi.json throws this:
INFO: 127.0.0.1:59046 - "GET /docs HTTP/1.1" 200 OK
INFO: 127.0.0.1:59046 - "GET /openapi.json HTTP/1.1" 500 Internal Server Error
ERROR: Exception in ASGI application
Traceback (most recent call last):
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/uvicorn/protocols/http/h11_impl.py", line 373, in run_asgi
result = await app(self.scope, self.receive, self.send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/uvicorn/middleware/proxy_headers.py", line 75, in __call__
return await self.app(scope, receive, send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/fastapi/applications.py", line 208, in __call__
await super().__call__(scope, receive, send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/applications.py", line 112, in __call__
await self.middleware_stack(scope, receive, send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/middleware/errors.py", line 181, in __call__
raise exc from None
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/middleware/errors.py", line 159, in __call__
await self.app(scope, receive, _send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/exceptions.py", line 82, in __call__
raise exc from None
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/exceptions.py", line 71, in __call__
await self.app(scope, receive, sender)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/routing.py", line 580, in __call__
await route.handle(scope, receive, send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/routing.py", line 241, in handle
await self.app(scope, receive, send)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/starlette/routing.py", line 52, in app
response = await func(request)
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/fastapi/applications.py", line 161, in openapi
return JSONResponse(self.openapi())
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/fastapi/applications.py", line 136, in openapi
self.openapi_schema = get_openapi(
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/fastapi/openapi/utils.py", line 387, in get_openapi
definitions = get_model_definitions(
File "/home/yash/.cache/pypoetry/virtualenvs/projects-api-qgm49pqx-py3.8/lib/python3.8/site-packages/fastapi/utils.py", line 24, in get_model_definitions
m_schema, m_definitions, m_nested_models = model_process_schema(
File "pydantic/schema.py", line 548, in pydantic.schema.model_process_schema
File "pydantic/schema.py", line 589, in pydantic.schema.model_type_schema
File "pydantic/schema.py", line 234, in pydantic.schema.field_schema
File "pydantic/schema.py", line 202, in pydantic.schema.get_field_info_schema
File "pydantic/schema.py", line 899, in pydantic.schema.encode_default
File "pydantic/json.py", line 95, in pydantic.json.pydantic_encoder
TypeError: Object of type 'type' is not JSON serializable
