uvicorn.run env_file Not Passed Correctly

[oliv10]

Initial Checks

• I confirm this was discussed, and the maintainers suggest I open an issue.
• I'm aware that if I created this issue without a discussion, it may be closed without a response.

Discussion Link

https://github.com/encode/uvicorn/discussions/2328

Description

When passing a .env file with the uvicorn.run command it does not properly pass its information on to the uvicorn and FastAPI application.

Example Code

### Test Code


import uvicorn
import fastapi
from pydantic_settings import BaseSettings
import argparse
import logging
from logging import getLogger


class Settings(BaseSettings):
    DEBUG: bool = False



SETTINGS = Settings()
app = fastapi.FastAPI()



Logger = getLogger("uvicorn")
if SETTINGS.DEBUG:
    Logger.setLevel(logging.DEBUG)
    Logger.debug("Debug Mode Enabled")
else:
    Logger.setLevel(logging.INFO)



@app.get("/")
async def root():
    if SETTINGS.DEBUG:
        return {"message": "DEBUG World"}
    else:
        return {"message": "Hello World"}


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("--env-file", type=str, default=".env")
    args = parser.parse_args()
    
    uvicorn.run(app, env_file=args.env_file)

.env file

DEBUG=True

Test Cases

Incorrect Output

python3 ./test_uvicorn.py

INFO:     Loading environment from '.env'
INFO:     Started server process [279760]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     127.0.0.1:40028 - "GET / HTTP/1.1" 200 OK

Correct Output

uvicorn test_uvicorn:app --env-file .env

INFO:     Loading environment from '.env'
DEBUG:    Debug Mode Enabled
INFO:     Started server process [280032]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
DEBUG:    DEBUG
INFO:     127.0.0.1:60288 - "GET / HTTP/1.1" 200 OK

Python, Uvicorn & OS Version

Running uvicorn 0.29.0 with CPython 3.12.2 on Linux

Important

• We're using Polar.sh so you can upvote and help fund this issue.
• We receive the funding once the issue is completed & confirmed by you.
• Thank you in advance for helping prioritize & fund our backlog.

[oliv10]

Maybe relates to #1319 and #1372.

[saparmuratx]

I faced similar problem trying to debug my FastAPI project.
uvicorn keeps ignoring specified --env-file

When uvicorn server is launched like this:

uvicorn src.main:app --reload --env-file src/.env 

with specified src/.env,
it seems to ignore specified env file at all and use global environment variables.

After some time trying to fix it, I have found the culprit.
VS Code automatically loads .env file from default workspace folder for Python.

I think if terminal session has environment variables uvicorn will use them regardless of specified .env file. So after changing the .env file, restarting of terminal is required to load new values.

[hanchchch]

I know it's a bit late to answer but leaving it for whom may ran into the same problem.

The problem is that the SETTINGS is a global variable which is defined whenever this code is imported/executed, since it's not wrapped as a function.

class Settings(BaseSettings):
    DEBUG: bool = False


SETTINGS = Settings()
app = fastapi.FastAPI()

Uvicorn loads the env file here, inside the uvicorn.run. SETTINGS is being define before you call uvicorn.run when the env file is not loaded yet. That's why your env file is not reflected to the SETTINGS.

To solve this problem you need to wrap the settings variable into a function.

def get_settings():
    return Settings()

Then, call it when it's obviously after uvicorn.run is already called.

@app.get("/")
async def root():
    # this is invoked when the http requests arrive here.
    # thus, this can not be invoked before the server started to run.
    if get_settings().DEBUG:
        return {"message": "DEBUG World"}
    else:
        return {"message": "Hello World"}

Even better with dependency injection.

from fastapi import Depends
from typing_extensions import Annotated

AppSettings = Annotated[config.Settings, Depends(get_settings)]

@app.get("/")
async def root(settings: AppSettings):
    if settings.DEBUG:
        return {"message": "DEBUG World"}
    else:
        return {"message": "Hello World"}