The big question I have is: Would being able to output debug messages to the web browser be useful enough to make it work implement?
Currently, the Koha logs are very verbose. If we replace all occurrences of 'warn' to use this module and display them to the web browser, the users will be unhappy. I think it is preferable to manage and encapsule potential errors and display an adapted message for each them. Yes I know it is a big work :-/ But simply it could be possible to display only error message. For developpers I think it is not very useful to display debug messages (just my opinion).
Could you test and sign-off my patch if you agree with the Koha::Utils::Logger module and/or propose changes ?
I think the option of outputting too much to the screen is better than not outputting enough. I think the one really useful area for screen output of debugging messages would be when selecting circulation rules. This is an area where I have had many libraries submitting bugs that were in reality just circulation rules not set up correctly. I think it would be good to have the GET debug flag choose a level of output. Stuff like circulation rules would be level 1 ( info ). I think you patch looks good, but switching it to log4perl would be better. Many here are suggesting they want to output to the syslog, which log4perl supports. In can output to stderr, syslong, and a log file simultaneously. Kyle