Winston not displaying error details

I think what you're missing is format.errors({ stack: true }) in winston.createLogger.

const logger = winston.createLogger({  level: 'debug',  format: format.combine(    format.errors({ stack: true }),    print,  ),  transports: [new transports.Console()],});

See this GitHub thread for more information.

The reason this is happening is because the interesting Error object properties, like .stack, are non-enumerable. Some functions check if the their parameters are Error instances, like console.error, and other functions ignore all non-enumerable properties, like winston.<log-level> and JSON.stringify.

> console.error(new Error('foo'))Error: foo    at repl:1:15    at Script.runInThisContext (vm.js:124:20)    ...(abbr)> JSON.stringify(new Error('foo'))'{}'

All that said, it's horrible usability to have an error logger essentially ignore errors... I just lost too much time to this.

A quick and dirty way would be to log err.stack:

logger.error(err.stack);

A more elaborate method would be to implement a custom format specifically for Error instances. There's some example code on how to implement that in this Github issue.

Using format.

const { combine, timestamp, label, printf } = winston.format;const myFormat = printf(info => {    if(info instanceof Error) {        return `${info.timestamp} [${info.label}] ${info.level}: ${info.message} ${info.stack}`;    }    return `${info.timestamp} [${info.label}] ${info.level}: ${info.message}`;});winston.createLogger({    level: "info",    format: combine(        winston.format.splat(),        label({ label: filename}),        timestamp(),        myFormat,    ),    transports: [    //    // - Write to all logs with level `info` and below to `combined.log`    // - Write all logs error (and below) to `error.log`.    //        new winston.transports.File({ filename: path.join(os.tmpdir(), "test", "test.log"), level: "info" }),    ],});