Fix a problem of raw option with handler

[Writtic]

• Using raw option with handler, the message is cutted last 1 length

When I test my application with loguru, I found something weird.

logger.add(
        sink=LogstashHandler(host, port, "my-app", tags),
        format=LOGSTASH_FORMAT,
        level=level
    )
logger.opt(raw=True).error("hello")

Result: {... 'message': 'hell' ...}

As you could see, If I use handler with raw option, I couldn't get full message on the log.
So I tried to find this solution then somewhat dealt with it with test code.

[Writtic]

Need to check other conditions of self._writer attributes.

[Delgan]

Awesome, thanks for reporting and investigating this issue!

So, to explain what is happening, one should look here:

loguru/loguru/_logger.py

Lines 716 to 717 in 9250317

	if not is_formatter_dynamic:
	message = message[:-1]

Why am I chopping the last char of the message? Because Loguru automatically adds "\n" at the end of the log messages:

loguru/loguru/_logger.py

Line 794 in 9250317

formatter = format + "\n{exception}"

However, standard logging does the same: Lib/logging/__init__.py#L1084

In order to prevent the message to be displayed with two trailing "\n", I remove the one added by Loguru, but only if the format is not a function (because if it is the case, Loguru does not automatically add the trailing "\n").

The bug occurs because the trailing "\n" is not added by Loguru if raw=True. In such case, there is no "\n" to remove, so the last character is wrongly chopped instead.

Here is a small code snippet to play with:

import logging
import sys
from loguru import logger

logger.remove()
logger.add(logging.StreamHandler(sys.stderr), format="{level.no} {message} [Not Chopped]")

logger.error("Allo?")
logger.opt(raw=True).error("hello")

Your solution may work but I would like to avoid having to dynamically check for attributes at run-time in emit(). Actually, there is a very easy solution: remove if not is_formatter_dynamic: message = message[:-1] and replace it with sink.terminator = "". I did not implement this solution is the first time because I wanted not to mutate the sink object, but this is maybe the best solution considering there is no other easy workaround. 😕

[Writtic]

Thank you for very specific and kind replying!
I'm glad to hear the reason of the problem and what your idea about my request is.
I also hoped to avoid amending object level, but I'm not familiar with the project, so I didn't come up with the better solution.

[Delgan]

I finally fixed this issue in 49c5560. The workaround was quite simple, I just needed to specialize "\n" terminator for both the format and the exception formatter (due to implementation details in logging.Handler). It worries me not to have thought about this sooner... 😁

Anyway, I merged the new unit tests you added, thanks! 😃