I hope fastapi can support TypeVar

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

from typing import TypeVar, Generic

from fastapi import Depends
from sqlalchemy.orm import Session

from app.core.database_engine.db_core import get_db
from app.core.table_class import HasIdTable, DateCreateTable, DateCreateUpdateTable

T = TypeVar('T', bound=HasIdTable)


class DbAdaptor(Generic[T]):
    def __init__(self, db: Session = Depends(get_db)):
        self.db = db

    def add(self, data_element: T, is_commit: bool = True) -> dict:
        if isinstance(data_element, DateCreateTable):
            data_element.create_stamp()
        self.db.add(data_element)
        if is_commit:
            self.db.commit()
        return data_element.get_dict()

    def read_by_id(self, id: int) -> T:
        rt: T = self.db.query(T).filter_by(id=id).first()
        return rt

@bp.post('/create', description='create data to table')
def create(dba: DbAdaptor[SampleTable] = Depends(), data: str = Body(..., embed=True)):
            """create data into the table"""
            data = SampleTable(data=data,
                               link=str(random.randint(0, 99999)),
                               title=data,
                               content=data)
            return dba.add(data)

Description

I’m sorry, I’m no English user but I want to achieve this function.

This is the code in my project, but guess what happened when I opened swagger.

This shouldn’t happen.

I just want to simplify the operation of the database.

I just want to make operating the database easier through my code.

Under normal circumstances, I can do this without thinking about more specific details.

Wanted Solution

I hope it can show a normal swagger.

Wanted Code

null

Alternatives

do not use the typevar, But it’s not fun.

Operating System

macOS

Operating System Details

No response

FastAPI Version

fastapi~=0.68.1

Python Version

python3.8

Additional Context

No response

[JeanArhancet]

I have opened a Pull Request for this issue. I used the functions of Pydantic to retrieve the arguments

[jakub-bacic]

I haven’t checked your code but we just had a similar issue in our project and… it seems that the issue is fixed with python 3.9. Try to check that first and see if that helps.