Deno's logger's formatter method doesn't allow not logging a string

[johndeighan]

In my logger config, I have 2 handlers, 'console' and 'file'. Each has its own custom formatter. Then I have a logger named 'debug' that invokes both of these handlers. What I want is to invoke the 'debug' logger with the name of the current main module when it's different than it was when the previous log was output. That way, when I look at the log file, I'll know when the main module was changed (e.g. when Deno.Output was used to execute an external script).

However, I don't want that information to appear in the console. I expected that if my console formatter returned undefined or null, it would prevent output to the console entirely. Unfortunately, it outputs either the string 'undefined' or 'null' instead. I can, in fact, return '' but then a newline still gets output to the console.

This feature request is to find some way to prevent output entirely in a custom formatter.

[bartlomieju]

Is this problem related to https://jsr.io/@std/log? Can you provide some reproduction code?