FastAPI 0.68.0 Breaks Usage of tuple in Input / Output compared to 0.67.0

[MarioIshac]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.

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Example Code

# main.py

import uvicorn
from fastapi import FastAPI, Form

app = FastAPI()

@app.post("/")
def hello(arg: tuple[int, int] = Form(...)) -> str:
    pass

if __name__ == "__main__":
    uvicorn.run("main:app", port=8080)

Description

1. Run pip install uvicorn fastapi==0.68.0.
2. Run python ./main.py
3. Hit localhost:8080/docs, observe internal server error with below validation errors:

pydantic.error_wrappers.ValidationError: 2 validation errors for OpenAPI
components -> schemas -> Body_hello__post -> properties -> arg -> items
  value is not a valid dict (type=type_error.dict)
components -> schemas -> Body_hello__post -> $ref
  field required (type=value_error.missing)

4. Run pip install fastapi==0.67.0
5. Hit localhost:8080/docs, observe that endpoint documentation is successfully generated.

Operating System

Linux

Operating System Details

Ubuntu 20.04

FastAPI Version

0.68.0 has bug, 0.67.0 does not have bug.

Python Version

3.9

Additional Context

Any use of tuple in an input (Form, and BaseModel as JSON) or output (BaseModel as JSON) results in above error.

[Mause]

What are you expecting a tuple in a form field to look like?

[MarioIshac]

What are you expecting a tuple in a form field to look like?

Same as it did in 0.67.0, the generated endpoint docs look like this:

[elrik75]

I use typing.Tuple for geolocation.

class Model(BaseModel):
    name: str
    location: Tuple[float, float]

This seems a legit use of tuple, no?

[HansBrende]

I am also having this same problem, which I fixed by downgrading to fastapi version 0.67.0. Specific stack trace details, etc: #3686 (I closed my issue as it was a duplicate of this issue).

[elrik75]

According to this: https://stackoverflow.com/questions/57464633/how-to-define-a-json-array-with-concrete-item-definition-for-every-index-i-e-a it's possible to have tuples in openapi3.1.

It could be great if @tiangolo could tell us if FastAPI will support Tuples again or if we need adapt our APIs. For now we are stuck in 0.67

[jessekv]

@Mause I have an API that uses tuples in a few places as well. At the moment it looks like I will be forced to pin to 0.67.0 indefinitely to avoid breaking changes to my API. Do you know if there is a plan to fix this regression?

[Mause]

@vdwees I'm not associated with the fastapi project so I can't help you sorry 😓