Breaking change in dependency type inspection in FastAPI 0.123.7 #14464
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Example Code# /// script
# requires-python = "==3.14.*"
# dependencies = [
# "fastapi==0.123.7",
# "uvicorn",
# ]
# ///
from __future__ import annotations
from typing import TYPE_CHECKING, Annotated
from fastapi import Depends, FastAPI
if TYPE_CHECKING:
from collections.abc import AsyncGenerator
app = FastAPI()
class DummyClient:
async def get_people(self) -> list:
return ["John Doe", "Jane Doe"]
async def close(self) -> None: ...
async def get_client() -> AsyncGenerator[DummyClient, None]:
client = DummyClient()
yield client
await client.close()
Client = Annotated[DummyClient, Depends(get_client)]
@app.get("/")
async def get_people(client: Client) -> list:
return await client.get_people()
if __name__ == "__main__":
import uvicorn
uvicorn.run(app, host="0.0.0.0", port=8000)DescriptionThis code works under FastAPI < 0.123.7, but fails with newer releases: traceback
Operating SystemmacOS Operating System DetailsNo response FastAPI Version0.123.9 Pydantic VersionMA Python Version3.14.0 Additional ContextMoving the from __future__ import annotations
+ from collections.abc import AsyncGenerator
- from typing import TYPE_CHECKING, Annotated
+ from typing import Annotated
from fastapi import Depends, FastAPI
- if TYPE_CHECKING:
- from collections.abc import AsyncGeneratorNote: seems like #11355 introduced the change. |
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Replies: 6 comments 6 replies
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I think #11355 should be reverted, given the very confusing effects it has (see here). |
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Agreed this is a breaking change, it also forces non-runtime requirements (e.g. type/stub files) to be installed within releases, bloating install size which shouldn't be required. e.g. |
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It looks like it is related: |
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Also have another repro without the use of |
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You didn't have that error because With changes you made it's now valid example that demonstrates the issue from another side. Thanks! Minimized code example could look like: main.py from __future__ import annotations
import typing as t
import fastapi
from .config import get_settings
if t.TYPE_CHECKING:
import config
app = fastapi.FastAPI()
@app.get("/")
async def dummy(
settings: config.Settings = fastapi.Depends(get_settings),
) -> str:
return "Dummy"config.py class Settings:
pass
def get_settings() -> Settings:
return Settings()With latest FastAPI version it raises |
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Thanks for the additional explaination. I have tested your reduced example, the relativ import I have updated my example based on your version above, but kept my version on a second branch. |
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Thanks for the very simple replicable example @edgarrmondragon! 🚀 I used it in the tests. I created an issue here for completeness: #14484 This should be solved by #14485 It's available in FastAPI 0.124.2, just released 🎉 |
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Thanks for the fix. Can confirm that my issue is also fixed. |
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Thanks for the quick fix @tiangolo! |
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Thanks for the very simple replicable example @edgarrmondragon! 🚀
I used it in the tests.
I created an issue here for completeness: #14484
This should be solved by #14485
It's available in FastAPI 0.124.2, just released 🎉