fix: append error cause when using logger.child()

[2013xile]

Add error.cause when cloning error info in logger.child()

[HenriqueSilverio]

Just tried to run it here and got "cause":{}.

Runtime

• Node.js: 22.12.0
• npm: 11.0.0

Minimum Working Example

const winston = require('winston')

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

const childLogger = logger.child()

const error = new Error('Something went wrong', { cause: new Error('The devil is in the details') })

childLogger.error(error)

Output

{"cause":{},"level":"error","message":"Something went wrong","stack":"Error: Something went wrong\n    at Object.<anonymous> (/home/Code/winston-debug/index.js:14:15)\n    at Module._compile (node:internal/modules/cjs/loader:1546:14)\n    at Object..js (node:internal/modules/cjs/loader:1689:10)\n    at Module.load (node:internal/modules/cjs/loader:1318:32)\n    at Function._load (node:internal/modules/cjs/loader:1128:12)\n    at TracingChannel.traceSync (node:diagnostics_channel:315:14)\n    at wrapModuleLoad (node:internal/modules/cjs/loader:218:24)\n    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:170:5)\n    at node:internal/main/run_main_module:36:49"}

[2013xile]

Hi @HenriqueSilverio ,
This is because the default console transport doesn’t output the cause information. I recommend to customize a transport. For example:

const winston = require('./lib/winston')

class CustomTransport extends winston.Transport {
  log(info, callback) {
    const { level, message, stack, cause } = info;
    console.error({
      level,
      message,
      stack,
    });
    if (cause) {
      console.error({
        level,
        message: cause.message,
        stack: cause.stack
      })
    }
    callback(null, true);
  }
}

const logger = winston.createLogger({
  format: winston.format.combine(
    winston.format.json(),
  ),
  transports: [
    new CustomTransport(),
  ],
})

const childLogger = logger.child()

const error = new Error('Something went wrong', { cause: new Error('The devil is in the details') })

childLogger.error(error)

[HenriqueSilverio]

Hi @2013xile!
Maybe I'm missing something, but if we need to create a custom transport for the error to show, what exactly is the PR fixing?

[2013xile]

Hi @2013xile! Maybe I'm missing something, but if we need to create a custom transport for the error to show, what exactly is the PR fixing?

Without the changes in this PR, even a custom transport cannot retrieve the cause object. The console transport cannot output the cause information because it does not parse the cause object. I prefer not to modify this, as everyone may have different requirements for how the cause information is output.

[HenriqueSilverio]

Without the changes in this PR, even a custom transport cannot retrieve the cause object.

Got it! I've tried here and it worked as you said. Thanks for clarifying that!