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.

Commit to Help

• I commit to help with one of those options 👆

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

[vdwees]

@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 😓

[vdwees]

@Mause sorry, thanks anyway

[vdwees]

I wonder if this old issue is related #1507

[HansBrende]

Is there any way to get @tiangolo 's attention on this issue? There are now at least 4 dupes of this issue (#3686, #3782, #3898, and #4168), and 2 open PRs (#3874 & #4169), each with exactly the same 1-line fix which works perfectly. We're all (anyone using tuples) stuck on version 0.67.0 until something is done...

[elrik75]

It's seems that FastAPI is not actively maintained anymore and nothing seems to be done to allow someone else to do it (source: #3970)
I guess we need to wait for a fork but this could take a lot of time.
I personally modified all the code that needed Tuples to a Dict with 2 keys.
By the way staying in 0.67.0 is not a big deal as there is almost no more evolution.

[vdwees]

It's seems that FastAPI is not actively maintained anymore and nothing seems to be done to allow someone else to do it (source: #3970)

I guess we need to wait for a fork but this could take a lot of time.

I personally modified all the code that needed Tuples to a Dict with 2 keys.

By the way staying in 0.67.0 is not a big deal as there is almost no more evolution.

I understand your frustration, I am also waiting for this to be fixed. However, I don't think your claim of FastAPI being unmaintained is true at all.

For better or for worse, FastAPI is a project that stands on the shoulders of several other projects. Advocating for changes and improvements in those projects takes time. See this comment: https://news.ycombinator.com/item?id=29484907

[yangyaofei]

@elrik75 I have the same thought. Look at the merged PR, most recent PR is doc translations and update dependencies.

Here #1507 (comment) is the answer of this, but I don't think that's is a good solution.

Patching with some workaround(like this PR) is better than waitting for support with bug

[tiangolo]

Thanks for the discussion everyone! This should be solved by #3874

It is available in FastAPI 0.73.0, released in the next hours. 🎉

For more context, check the last comment there: #3874 (comment)

---

In short, using tuples now won't break the rest of Swagger UI.

And although they are supported by OpenAPI 3.1.0, Swagger UI doesn't support OpenAPI 3.1.0 yet. Even though FastAPI already has a couple of corner cases where it is more compatible with 3.1.0, I can't change the generated version yet, as Swagger UI wouldn't render it at all.

So, you can continue using tuples with FastAPI 0.73.0, those tuples won't always be properly rendered in Swagger UI (as they have never been), but now that won't break the rest of Swagger UI, and you will get the proper validation, etc. 🎉

[martinezpl]

This issue is solved and can be closed.

[acidjunk]

@MarioIshac can you close the issue?

[github-actions]

Assuming the original need was handled, this will be automatically closed now. But feel free to add more comments or create new issues or PRs.