Combine child metadata with additional metadata

I’m not sure this is a bug or feature request. I’ll use the bug template since it also contains the behavior I’d expect.

Please tell us about your environment:

• winston version?
  • winston@2
  • winston@3
• node -v outputs: v12.14.0
• Operating System? (Windows, macOS, or Linux) Linux
• Language? (all | TypeScript X.X | ES6/7 | ES5 | Dart) ES6/7

What is the problem?

There seems to be no way to combine child metadata with additional properties. In fact, I find the multiple api signatures in which one can log a message to be quite conflicting/confusing. For example, consider this code:

const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.printf(({ message, prefix}) => `[${prefix}]: ${message}`),
  defaultMeta: { prefix: 'root' },
  transports: [new winston.transports.Console()],
});

logger.info('foo 1', { foo: 'bar' });
logger.log('info','foo 2');
logger.log('info','foo 3', {});
logger.log({ level: 'info', message: 'foo 4' });

const childLogger = logger.child({ prefix: 'child' });
childLogger.info('foo 5', { foo: 'bar' });
childLogger.log('info','foo 6');
childLogger.log('info','foo 7', {});
childLogger.log({ level: 'info', message: 'foo 8' });

All of these are valid, but produce different/unexpected results:

[root]: foo 1
[undefined]: foo 2
[root]: foo 3
[root]: foo 4
[root]: foo 5
[child]: foo 6
[root]: foo 7
[root]: foo 8

What do you expect to happen instead?

I can’t really find an api reference, so it’s hard to know what is to be expected and what not. But I would expect that when I create a child logger with metadata, the metadata acts in the way the default metadata on the logger works. Because now, there is no way to add in additional properties in a log call, without losing the metadata passed in to the child logger.

So I would expect that I can still call childLogger.log('info', 'message', { additionalProp: 'foo' }) and still have the prefix=child property in the metadata. And in fact, I would expect this to be the case for any of the example calls to childLogger.

[traceon]

@aressler38 I took a more radical and seemingly consistent approach in #1879. Reused your test though.

[maverick1872]

Closing as this issue is being consolidated into #2029