[RFC] Pluggable log handler

Would you consider a PR that implemented support for globally defaulting log to something other than process.stderr? The way I’d expect this to work is debug would default to stderr unless process[Symbol.for(‘DEBUG_LOG’)] was set. Of course the local self.log would always take precedence.

The motivation for this feature is to allow an application to redirect all debug output to a logger of its choice, without knowing which all dependencies utilize debug.

I’ve chosen a global Symbol to circumvent the issue of multiple versions of debug in codebase.

Happy to submit this. Thoughts?

[Qix-]

It might be much more practical to just have a top level function on the debug instance. However, it’s usually an anti-pattern to modify a package’s state in a way that affects other packages.

EventEmitters are a good candidate here, too.

const debug = require('debug');

debug.on('log', msg => writeToSomeStream(msg));

[Qix-]

Doing a bit of poking around on this today, this appears to be soft-blocked by nodejs/node#40110. Not a deal-breaker but it’ll be less than advantageous without allowing users to do this with ESM modules.

The other issue is code-based linkage. If you add a handler via code instead of pre-loading modules, then we’ll run into the issue of libraries pre-loading their own handlers and causing unexpected output or mis-routed output (potentially) - something that, given the ubiquity of this package, simply won’t do.

There needs to be a way to either prevent or disable added log handlers in application code.