format.errors not working on transport level

Please tell us about your environment:

• winston version?
  • winston@2
  • winston@3
• node -v outputs: v12.16.1
• Operating System? macOS
• Language? TypeScript ^3.9.7

What is the problem?

When I use format.errors({stack: true}) on logger configuration level, it works as expected. The logger parses JavaScript Error object and prints correctly.

import { createLogger, format, transports } from 'winston';

const logFormatter = format.printf((info) => {
  let { timestamp, level, stack, message } = info;
  message = stack || message;
  return `${timestamp} ${level}: ${message}`;
});

const logToConsole = createLogger({
  level: 'info',
  format: format.errors({ stack: true }),
  transports: [
    new transports.Console({
      format: format.combine(format.colorize(), format.simple(), format.timestamp(), logFormatter),
    }),
  ],
});

const err = new Error('network');
logToConsole.error(err);

Output:

2021-01-22T06:55:25.500Z error: Error: network
    at Object.<anonymous> (/Users/ldu020/workspace/github.com/mrdulin/expressjs-research/src/stackoverflow/65822479/index.ts:19:13)
    at Module._compile (internal/modules/cjs/loader.js:1158:30)
    at Module.m._compile (/Users/ldu020/workspace/github.com/mrdulin/expressjs-research/node_modules/ts-node/src/index.ts:858:23)
    at Module._extensions..js (internal/modules/cjs/loader.js:1178:10)
    at Object.require.extensions.<computed> [as .ts] (/Users/ldu020/workspace/github.com/mrdulin/expressjs-research/node_modules/ts-node/src/index.ts:861:12)
    at Module.load (internal/modules/cjs/loader.js:1002:32)
    at Function.Module._load (internal/modules/cjs/loader.js:901:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12)
    at main (/Users/ldu020/workspace/github.com/mrdulin/expressjs-research/node_modules/ts-node/src/bin.ts:227:14)
    at Object.<anonymous> (/Users/ldu020/workspace/github.com/mrdulin/expressjs-research/node_modules/ts-node/src/bin.ts:513:3)

I think the format.errors({ stack: true }) can be used on transport level too. But it doesn’t.

import { createLogger, format, transports } from 'winston';

const logFormatter = format.printf((info) => {
  let { timestamp, level, stack, message } = info;
  message = stack || message;
  return `${timestamp} ${level}: ${message}`;
});

const logToConsole = createLogger({
  level: 'info',
  // format: format.errors({ stack: true }),
  transports: [
    new transports.Console({
      format: format.combine(
        format.errors({ stack: true }),
        format.colorize(),
        format.simple(),
        format.timestamp(),
        logFormatter,
      ),
    }),
  ],
});

const err = new Error('network');
logToConsole.error(err);

Output:

2021-01-22T06:58:00.582Z error: undefined

What do you expect to happen instead?

I think the configuration of the logger level is a global configuration, and the configuration of the transport level is the configuration for each transport, and has the highest priority, covering the global configuration.

They are should have the same output.

[MinusFour]

The winston-transport module “clones” the info object being formatted:

https://github.com/winstonjs/winston-transport/blob/e4a6ce1a0b788d4fe56b4be94c30a3bebe96c2e2/index.js#L90-L94

This leads to only copying enumerable properties, which on Error objects not even message is. So the object itself is pretty much blank at that point (at the very least devoid of any Error properties).

Since the error formatter is expecting an Error (or at least an error object inside a message property) it does nothing.

An alternative that could work as it is right now:

logToConsole.error({
   message: err
});

Which I guess you can monkey patch on the class instance.

const logError = logToConsole.error.bind(logToConsole);
logToConsole.error = (message) => logError({ message });

I’ll just point out that the log formatter (that is, the one that’s on the logger itself) does not receive a copy of an object but the object itself.

[OktarinTentakel]

Any news on this?