Can't set global `log()` function overriding namespaces ones

[piranna]

On the example located at https://github.com/debug-js/debug#output-streams, it shows that's possible to set custom log() functions for each namespace, but also that setting it directly on the debug module takes precedence and will be used instead of the namespace ones. This is specially useful in my use case, since I want to capture Mediasoup debuging Logger and redirect it to Moleculer logger. Problem is that according to

debug/src/common.js

Lines 112 to 113 in c0805cc

	const logFn = self.log || createDebug.log;
	logFn.apply(self, args);

namespaces log() function has absolute priority, so it's not possible to do it globally, and it's not possible to directly bind on top of Mediasoup Loggers since they are private, so I'm in an end road.

Since the linken example at https://github.com/debug-js/debug/blob/master/examples/node/stdout.js doesn't exists too, I'm not sure if the documentation is outdated or wrong, or if setting debug.log() should effectively override per-namespace log() function and this is in fact a bug. Besides fixing this one way or another, how can I solve my problem of redirect Mediasoup log messages to Moleculer?

[Qix-]

Yes but self.log shouldn't be set to anything.

Welcome to Node.js v17.3.1.
Type ".help" for more information.
> const debug = require('debug');
undefined
> debug.log
[Function: log]
> d1 = debug('foo:bar')
[Function: debug] {
  namespace: 'foo:bar',
  useColors: true,
  color: 4,
  extend: [Function: extend],
  destroy: [Function: deprecated],
  enabled: [Getter/Setter],
  inspectOpts: {}
}
> d1.log
undefined
> d1.enabled = true
true
> d1('test')
  foo:bar test +0ms
undefined
> debug.log = (...args) => console.error('MY DEBUG:', ...args);
[Function (anonymous)]
> d1('test')
MY DEBUG:   foo:bar test +24s
undefined

This works for me on the latest version. Can you reproduce that locally?

[piranna]

This works for me on the latest version.

It's not the same case here, that works because d1.log is undefined, but at Mediasoup https://github.com/versatica/mediasoup/blob/4783b3dde93d43b5b120a8088af873aa5661202f/node/src/Logger.ts#L27-L29 d1.log is set to a function, the same as what the example in the docs says:

debug/README.md

Lines 254 to 272 in c0805cc

	```js
	var debug = require('debug');
	var error = debug('app:error');
	// by default stderr is used
	error('goes to stderr!');
	var log = debug('app:log');
	// set this namespace to log via console.log
	log.log = console.log.bind(console); // don't forget to bind to console!
	log('goes to stdout');
	error('still goes to stderr!');
	// set all output to go via console.info
	// overrides all per-namespace log settings
	debug.log = console.info.bind(console);
	error('now goes to stdout via console.info');
	log('still goes to stdout, but via console.info now');
	```

With d1.log set to a function as debug documentation example does (and also Mediasoup does too), it fails.

[piranna]

How can I help you with that? It's tagged as question, but it's also a bug on docs and/or actual implementation. How can we move this forward?

[Qix-]

I'm not sure what you want. If you specify a logger on individual debug instances, of course it will override the global logger. That's well defined.

What behavior would you like to see happen?

[piranna]

What behavior would you like to see happen?

According to the docs example, if you define a logger in debug instance, it will override all the ones from its parent debug instances, but if you define a global logger, it will override all the debug instances. The example in the docs is very explicit about this behaviour:

debug/README.md

Lines 254 to 272 in c0805cc

	```js
	var debug = require('debug');
	var error = debug('app:error');
	// by default stderr is used
	error('goes to stderr!');
	var log = debug('app:log');
	// set this namespace to log via console.log
	log.log = console.log.bind(console); // don't forget to bind to console!
	log('goes to stdout');
	error('still goes to stderr!');
	// set all output to go via console.info
	// overrides all per-namespace log settings
	debug.log = console.info.bind(console);
	error('now goes to stdout via console.info');
	log('still goes to stdout, but via console.info now');
	```

[Qix-]

You're right, GitHub has a scrollbar on mobile and I missed it in your other comment. My apologies.

PR welcome to fix the docs. There isn't a great way to fix this that won't break a bunch of people unfortunately. I need to think about how to approach this for v5.

[piranna]

Thing is, it seems like this was the previous behaviour, but can't find the actual reference.

[shryao1]

This is interesting