Child property binding duplicated when property appears in log statement

[jcald1]

Summary

I set up a property ("a") in the child binding then I logged an object containing that same property name ("a"). Instead of overriding the binding value, the key is duplicated in the JSON.

Code

const logger = require('pino')()
logger.info('test')

const child = logger.child({a: 'prop', b: 'prop' })
child.info('test')
child.info({a: 'new prop'})

Output

{"level":30,"time":1554156372574,"pid":9088,"hostname":"MLP-0U8HV2H","msg":"test","v":1}
{"level":30,"time":1554156372575,"pid":9088,"hostname":"MLP-0U8HV2H","a":"prop","b":"prop","msg":"test","v":1}
{"level":30,"time":1554156372575,"pid":9088,"hostname":"MLP-0U8HV2H","a":"prop","b":"prop","a":"new prop","v":1}

[davidmarkclements]

Yes this is expected behavior, it’s a performance trade off

[davidmarkclements]

It’s documented here http://getpino.io/#/docs/child-loggers?id=duplicate-keys-caveat

[github-actions]

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