Add default log_config on uvicorn.run()

[Kludex]

I broke the logs because of this. 😞

I don't know how I didn't catch this... It's too simple...

Anyway, moment of shame here. This application doesn't show any logs:

import uvicorn
from fastapi import FastAPI

app = FastAPI() 
@app.get("/")
def index(): 
    return {"home": "index"}

if __name__==  "__main__": 
    uvicorn.run("main:app", port=8100)

The reason is that I've set the default of log_config to None, instead of LOGGING_CONFIG.

EDIT: The funny thing is that I noticed this behavior, and I thought the problem was the computer (mac)... 🤦

[adriangb]

Was this the previous default? Where (in what commit) was it changed?

[adriangb]

Suggested change

	log_config: typing.Optional[typing.Union[dict, str]] = LOGGING_CONFIG,
	log_config: typing.Optional[typing.Union[typing.Mapping[str, Any], str]] = LOGGING_CONFIG,

At least this way we'll get an error from the type checker if we try to mutate the default argument.

[Kludex]

I'm going to merge #1539 after this PR.

[Kludex]

But it wouldn't make any difference for here...

[Kludex]

Default values were added on: #1423

[adriangb]

I see, so before we were just setting it to this if it wasn't in kwargs:

uvicorn/uvicorn/main.py

Line 405 in 4e8781c

"log_config": LOGGING_CONFIG if log_config is None else log_config,

So I guess we just got it wrong in #1423

This is an easy 👍 then.

[adriangb]

One last thing: should we remove Optional then? You either use the default mapping or you pass in a mapping. Or does None have a meaning now?

[Kludex]

None always had a meaning. Which is to not set what is in the LOGGING_CONFIG i.e. just not set anything for loggers...

The mistake here was to set None as default on the run().

[adriangb]

But before if you passed None you got LOGGING_CONFIG so None had not meaning:

uvicorn/uvicorn/main.py

Line 422 in 11d28e2

log_config=LOGGING_CONFIG if log_config is None else log_config,

[Kludex]

Via CLI it was never supposed to accept None. But via code, it was always allowed:

uvicorn/uvicorn/config.py

Line 399 in 11d28e2

if self.log_config is not None:

[adriangb]

Hmm okay ✅