Node.js pino logger show caller filename and line number

pino_trace_caller.js

import path from 'path'
import pino from 'pino'

const STACKTRACE_OFFSET = 2
const LINE_OFFSET = 7
const { symbols : { asJsonSym} } = pino

function traceCaller (pinoInstance) {
  const get = (target, name) => name === asJsonSym ? asJson : target[name]

  function asJson (...args) {
    args[0] = args[0] || Object.create(null)
    args[0].caller = Error().stack.split('\n').filter(s => !s.includes('node_modules/pino') && !s.includes('node_modules\\pino'))[STACKTRACE_OFFSET].substr(LINE_OFFSET).replace(path.resolve(__dirname, '..'), '')
    return pinoInstance[asJsonSym].apply(this, args)
  }

  return new Proxy(pinoInstance, { get })
}

const logger = traceCaller(pino({
  level: 'debug',
  prettyPrint: {
    colorize: true,
  }
}))

Not so scalable solution, this doesnt work if pino actual methods(info, child etc) are inside some wrappers, sure in such cases it logs line and file of an actual wrapper

Love this! Thanks - thanks - thanks! 👍
As a node ESM version, I had issues with __dirname, also substr() should be replaced by substring()

I'm using dirname(import.meta.url) as a workaround, if in a subfolder, you can call dirname twice
Here's my take on traceCaller, I also modernized the pino instance creation since "prettyPrint" is deprecated.

import { pino } from 'pino'
import { dirname } from 'path'

const STACKTRACE_OFFSET = 2
const LINE_OFFSET = 7
const { symbols: { asJsonSym } } = pino

function traceCaller (pinoInstance) {
  const get = (target, name) => name === asJsonSym ? asJson : target[name]

  function asJson (...args) {
    args[0] = args[0] || Object.create(null)
    args[0].caller = Error().stack.split('\n')
      .filter(s => !s.includes('node_modules/pino') && !s.includes('node_modules\\pino'))[STACKTRACE_OFFSET]
      .substring(LINE_OFFSET).replace(dirname(import.meta.url) + '/', '')

    return pinoInstance[asJsonSym].apply(this, args)
  }

  return new Proxy(pinoInstance, { get })
}

const logger = traceCaller(pino({
  level: 'debug',
  transport: {
    target: 'pino-pretty',
    options: {
      ignore: 'time,pid,hostname'
    }
  }
}))

I wrote a version for Node which provides more information: https://gist.github.com/Caellian/53c91f78f9f54146edc73b4200cd4775

I needed the whole trace and have it be structured. Only works for Node (didn't test in browsers).

But in general, pino allows mixins (now?), so it's better to use those than wrapping the logger:

pino({
  // rest
  mixin: (base, level, logger) => {
    return { /* additional data; added from each log statement */ };
  },
}),

This makes it much more convenient to add trace information.