Bug with async callable class dependency in fastapi>=0.123.6

[tanguy-michardiere]

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Example Code

from typing import Annotated

from fastapi import Depends, FastAPI
from fastapi.dependencies.models import Dependant
from uvicorn import run


class Dependency:
    def __init__(self):
        print("init")

    async def __call__(self):
        print("call")


print(Dependant(Dependency).is_coroutine_callable)
# `True` with fastapi>=0.123.6
# `False` with fastapi<0.123.6

app = FastAPI()


@app.get("/")
async def route(*, dependency: Annotated[Dependency, Depends()]):
    await dependency()


run(app)

# then `curl localhost:8000`

Description

File ".venv/lib/python3.14/site-packages/fastapi/dependencies/utils.py", line 647, in solve_dependencies
    solved = await call(**solved_result.values)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'Dependency' object can't be awaited

fastapi.dependencies.models.Dependant incorrectly identifies Dependency as a "coroutine callable", and solve_dependencies then tries to await an instance of Dependency.

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.123.7

Pydantic Version

2.12.5

Python Version

3.14.1

Additional Context

No response

[tirkarthi]

Related : #14448 , #14434

[YuriiMotov]

Here is my attempt to fix this: #14458