MemoryHandler can't be setup through a DictConfig if any other logger is setup after it

[TheSylex]

Bug report

Bug description:

This is the logging that's failing.

LOGGING = {
    "version": 1,
    "disable_existing_loggers": False,
    "handlers": {
        "fine-logger1": {
            'level': logging.INFO,
            'formatter': 'verbose-console',
            'class': 'logging.StreamHandler',
            'stream': 'ext://sys.stdout',
        },
        "fine-logger2": {
            "level": logging.INFO,
            "class": "logging.FileHandler",
            "filename": Path("logs/somefilename.log"),
            "mode": "a",
            "formatter": "verbose",
        },
        "fine-logger3": {
            "level": logging.DEBUG,
            "class": "logging.FileHandler",
            "filename": Path("logs/errors/somefilename.log"),
            "delay": True,
            "formatter": "verbose",
        },
        "bugged-logger3": {
            "level": logging.DEBUG,
            "class": "logging.handlers.MemoryHandler",
            "capacity": 9999999,
            "flushLevel": logging.ERROR,
            "target": "fine-logger3",
            "flushOnClose": False,
        },
    },
    "loggers": {
        "bug-logger": {
            "handlers": ["fine-logger1", "fine-logger2", "bugged-logger3"],
            "level": logging.DEBUG,
            "propagate": True
        },
    },
}

After it's been setup, if any other handler is setup afterwards (in my case it's the copernicusmarine logger) the handler bugged-logger3 will have a None inside its target field, as every handler that's not incremental will delete existing unused handlers.

I've dug into the source code of logging and I think I've tracked down where this is happpening, but I'm not really sure on how to fix it. In the config file python3.11/logging/config.py in the configure() function there's a call to _clearExistingHandlers():

            else:
                disable_existing = config.pop('disable_existing_loggers', True)

                _clearExistingHandlers() <-----

                # Do formatters first - they don't refer to anything else
                formatters = config.get('formatters', EMPTY_DICT)
                for name in formatters:
                    try:
                        formatters[name] = self.configure_formatter(
                                                            formatters[name])

If we comment this line, it works completely fine. But I guess this just keeps handlers loaded in memory and that's not a proper solution.

CPython versions tested on:

3.11

Operating systems tested on:

Linux

[picnixz]

Can you test with 3.12+? 3.11 only receives security fixes so we wouldn't correc this bug in 3.11 if there is one.

[TheSylex]

Sorry for the delay, I tested it on 3.12 and it's still happening.

[picnixz]

I'll just keep the type-bug label since it also affects previous versions. So I'll be assuming that it should be backported to all bug-fixes branches.