[Bug]: splat formatter overrides message property, sometimes

[shawnjones253]

The problem

When using the splat formatter, handling of message properties in meta objects is different than without. Although the docs are technically correct in both cases, it seems weird that the behavior is different with and without splat.

Without splat, docs say meta objects are handled as follows (link):

NOTE: any { message } property in a meta object provided will automatically be concatenated to any msg already provided: For example the below will concatenate 'world' onto 'hello':

logger.log('error', 'hello', { message: 'world' });
logger.info('hello', { message: 'world' });

With splat, docs say meta objects are handled as follows (link):

Any additional splat parameters beyond those needed for the % tokens (aka "metas") are assumed to be objects. Their enumerable properties are merged into the info.

What version of Logform presents the issue?

v2.4.2

What version of Node are you using?

v14.16.1

If this worked in a previous version of Logform, which was it?

No response

Minimum Working Example

With splat

const logger = winston.createLogger({
  format: (() => {
    return combine(
      splat(),
      json()
    );
  })(),
  transports: [new winston.transports.Console()]
});

// looks contrived, but npm's `Request` package throws errors that looks like this
const err = {
  message: "msg2"
}
logger.error('msg1', err)

// outputs:
// {"level":"error","message":"msg2"}

Without splat

const logger = winston.createLogger({
  format: (() => {
    return combine(
      json()
    );
  })(),
  transports: [new winston.transports.Console()]
});

const err = {
  message: "msg2"
}
logger.error('msg1', err)

// outputs:
// {"level":"error","message":"msg1 msg2"}

EDIT: strangely, this problem doesn't occur with regular Error objects, even with splat (maybe because Error's properties are not enumerable?):

// boilerplate same as "with splat" from above

logger.error('msg1', new Error('msg2'))
// outputs: 
// {"level":"error","message":"msg1 msg2","stack":"Error: msg2 ..." }

Additional information

Maybe applicable to winstonjs/winston#2072

🔎 Search Terms

splat format message

[bertho-zero]

This is due to:

https://github.com/winstonjs/winston/blob/3998df01449da35a60cf4b90730b91f4b2466bc5/lib/winston/logger.js#L235-L255

This processing should not exist and should be done by format if desired.