openapi render crashes with response_class of Tuple

[toppk]

Describe the bug
openapi schema generation crashes when given a tuple as response_class. all the other behavior is working properly, just the openapi renderer. I think this is because tuples in openapi aren't supported that well. see this comment for a suggestion

OAI/OpenAPI-Specification#1026 (comment)

There should be some way to properly degrade this.

To Reproduce
Steps to reproduce the behavior:

1. run this code:
   ====
   from fastapi import FastAPI
   from pydantic import BaseModel
   from typing import Tuple

class Test(BaseModel):
name: str

app = FastAPI()

@app.get("/", response_model=Tuple[bool,Test])
async def root():
return True, {'name': 'Ken'}

2. navigate to h**p://localhost:8000/docs

Expected behavior

I'd expect openapi docs

import fastapi
print(fastapi.version)
0.35.0

(fastapi) [toppk@static fastapi]$ python --version
Python 3.6.9

• Python version, get it with:

python --version

Additional context
Add any other context about the problem here.

For reference here is the ouput I'm getting on the console:

$ uvicorn test-fastapi:app
INFO: Started server process [1976904]
INFO: Waiting for application startup.
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: ('127.0.0.1', 56070) - "GET / HTTP/1.1" 200
INFO: ('127.0.0.1', 56070) - "GET /docs HTTP/1.1" 200
INFO: ('127.0.0.1', 56070) - "GET /openapi.json HTTP/1.1" 500
ERROR: Exception in ASGI application
Traceback (most recent call last):
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/uvicorn/protocols/http/httptools_impl.py", line 375, in run_asgi
result = await app(self.scope, self.receive, self.send)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/applications.py", line 133, in call
await self.error_middleware(scope, receive, send)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/middleware/errors.py", line 177, in call
raise exc from None
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/middleware/errors.py", line 155, in call
await self.app(scope, receive, send)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y/lib/python3.6/site-packages/starlette/exceptions.py", line 73, in call
raise exc from None
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/exceptions.py", line 62, in call
await self.app(scope, receive, sender)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/routing.py", line 592, in call
await route(scope, receive, send)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/routing.py", line 208, in call
await self.app(scope, receive, send)
File "/home/toppk/.local/share/virtualenvs/fastapi-R7xES2y_/lib/python3.6/site-packages/starlette/routing.py", line 41, in app
response = await func(request)
File "./fastapi/applications.py", line 87, in openapi
return JSONResponse(self.openapi())
File "./fastapi/applications.py", line 79, in openapi
openapi_prefix=self.openapi_prefix,
File "./fastapi/openapi/utils.py", line 272, in get_openapi
return jsonable_encoder(OpenAPI(**output), by_alias=True, include_none=False)
File "pydantic/main.py", line 270, in pydantic.main.BaseModel.init
File "pydantic/main.py", line 697, in pydantic.main.validate_model
pydantic.error_wrappers.ValidationError: 7 validation errors
paths -> / -> get -> responses -> default
field required (type=value_error.missing)
content -> application/json -> schema -> items
value is not a valid dict (type=type_error.dict)
content -> application/json -> schema -> items
value is not none (type=type_error.none.allowed)
content -> application/json -> schema -> $ref
field required (type=value_error.missing)
content -> application/json -> schema
value is not none (type=type_error.none.allowed)
responses -> 200 -> content
value is not none (type=type_error.none.allowed)
paths -> / -> get
value is not none (type=type_error.none.allowed)

[toppk]

here is a copy of the test case for reference.
test-fastapi.py.txt

[haizaar]

@toppk
It will really help if you apply a proper formatting to your issue.

[dmontagu]

@toppk The closest you can get with the openapi spec is probably equivalent to what is (or should be) generated by:

from pydantic import conlist

@app.get("/", response_model=conlist(Union[bool,Test], min_items=2, max_items=2))

(Note: I don't think this is actually generating the complete openapi schema properly; the min/max items count is not specified and I'm not exactly sure why.)

But given the weak support for tuple in openapi spec, 1) I'm not sure it makes sense for FastAPI to support this, and 2) I would strongly preference creating a model for your response with named fields, rather than returning a tuple. If you are creating the server it seems like this should be within your control (unless you have backwards compatibility requirements).

[tiangolo]

@toppk as @dmontagu , tuples with exact values inside are explicitly unsupported by OpenAPI (there are notes stating that in the spec).

So, yeah, I think the best you can do is something like what @dmontagu suggests. Or better, if you can, make it a Pydantic model with 2 fields. It would also probably be a lot easier to use for your API users.

[github-actions[bot]]

Assuming the original issue was solved, it will be automatically closed now. But feel free to add more comments or create new issues.