Traceback is being logged unexpectedly

[Jakobovski]

I am trying to log with a custom JSON serialization and include the traceback and exception details in the JSON. I used patch() in order to do this.

Unexpectedly, unless i add the following line record['exception'] = None to patching() loguru will log the traceback in a non-JSON format even though I am using format="{extra[serialized]}"

See the code below

Am i doing something wrong or is this a bug?

import sys
import traceback

from loguru import logger

def serialize(record):
    error = record["exception"]
    if error:  # only set when exception.
        exception = {
            "type": error.type.__name__,
            "value": str(error.value),
            "traceback": "".join(traceback.format_exception(*error)),
        }
    else:
        exception = None

    subset = {
        "timestamp": record["time"].timestamp() * 1000,  # Should be in milliseconds for Datadog
        "message": record["message"],
        "level": record["level"].name,
        "status": str(record["level"].name),
        "logger": {"thread_name": str(record["thread"].name)},
        "file": f"{record['file']}",
        "function": f"{record['function']}",
        "line": f"{record['line']}",
        "module": f"{record['module']}",
        "name": f"{record['name']}",
        "process": f"{record['process']}",
        "thread": f"{record['thread']}",
        "exception": exception
    }
    return json.dumps(subset)

def patching(record):
    record["extra"]["serialized"] = serialize(record)
   # record['exception'] = None

logger.remove(0)  # Remove the original logger
logger = logger.patch(patching)
logger.add(sys.stdout, format="{extra[serialized]}")

def log_exception():
    try:
        open("fakefile.txt")
    except:
        logger.exception('')

log_exception()

[Delgan]

Hey @Jakobovski.

When format is a str, Loguru automatically appends "\n{exception}" to the format for convenience.

You can disable this by using a formatting function instead of a string:

logger.add(sys.stdout, format=lambda r: "{extra[serialized]}")