carp warn user from perspective of caller and already ignore Log::Log4perl::Appender-Class

[Sadrak]

The carp()-Message from Log::Log4perl::Appender jump over the important package who call the log-method and report from the next package. Simple remove the increase for $Carp::CarpLevel fix the problem.

From the Carp pod for carp():

# warn user (from perspective of caller)
carp "string trimmed to 80 chars";

Short example:

$ cat <<EOF > test.pl 
package Test;
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init($ERROR);
sub test { ERROR undef; }
package main;
Test::test();
EOF

$ perl test.pl 
Warning: Log message argument #1 undefined at test.pl line 6.
Use of uninitialized value in join or string at /usr/local/lib/perl5/site_perl/5.32.1/Log/Log4perl/Appender.pm line 189.
2021/03/05 07:33:45

This should say the error occur in line 4 not line 6.

[mohawk2]

This would be a break in the API; $caller_depth is documented in the FAQ in several places. From an application's point of view, it's going to be rare that a logger-calling function is directly responsible for the undef being passed into Log4perl, instead it will normally be due to the function's caller (e.g. in your example, it might be because it should have passed an argument and didn't).

I'm not totally opposed to this idea, but you need to make a stronger case that such a change would be worth the harm it would cause.