Unhelpful error message from logging.config.FileConfig can be improved

[vsajip]

Feature or enhancement

If a configuration file does not exist, the error raised by logging.config.fileConfig doesn't say that the file doesn't exist, instead suggesting that the file has an invalid format. This should be improved so that the correct error message is provided.

Pitch

The improved error message will guide a user to an error such as a typo in the filename more quickly. See for example this question.

Linked PRs

• gh-103606: Improve error message from logging.config.FileConfig #103628
• [3.11] gh-103606: Improve error message from logging.config.FileConfig (GH-103628) #104687
• gh-103606: raise RuntimeError if config file is invalid or empty #104701

[Agent-Hellboy]

Hi, @vsajip can I try to fix this?

[arhadthedev]

@Agent-Hellboy It's an open project, no preliminary assignment is required. The only thing you need is to follow the contributor's manual at https://devguide.python.org/ where conventions and processes are described.

[Agent-Hellboy]

okay, sure

[Agent-Hellboy]

Hi @arhadthedev
my approach would be to check the return value of cp.read(fname, encoding=encoding)

cpython/Lib/logging/config.py

Line 71 in d1e4917

cp.read(fname, encoding=encoding)

It uses configparser to parse the configuration files which suppresses the OSError but it returns an empty list if the file is not present

cpython/Lib/configparser.py

Line 665 in d1e4917

def read(self, filenames, encoding=None):

I will raise a PR which will raise ValueError that the file is not present and will try to include a test for the same

[vsajip]

Wouldn't it be simpler to use e.g. os.path.exists() and then throw a FileNotFoundError if the file doesn't exist? That would be the approach I would have taken.

[arhadthedev]

Because of the easier to ask for forgiveness than permission principle with the very os.path.exists() as an example:

import os

# violates EAFP coding style
if os.path.exists("file.txt"):
    os.unlink("file.txt")

[vsajip]

Yes, but the "file not found" message/FileNotFound exception are more informative than a generic "invalid file" when the file doesn't exist. It's a small point, I suppose; it's easier to ask for forgiveness, but that doesn't mean it's a cast-iron rule.

[Agent-Hellboy]

okay, I will raise FileNotFound before giving the file to the config parser

cpython/Lib/logging/config.py

Line 63 in 6be7aee

if isinstance(fname, configparser.RawConfigParser):

why should I try to parse a file which is not present

[gpshead]

I left some comments on the merged PR... ValueError isn't the right exception to use for things external to the process not related to the variable value itself. I suggest RuntimeError if you don't have your own Error exception class.

[Agent-Hellboy]

sure @gpshead, I will raise a PR

[gpshead]

thanks!