[Bug]: cannot extend winston.logger

[tomaswarynyca]

🔎 Search Terms

class extend, extend logger

The problem

TypeError: Class extends value undefined is not a constructor or null

What version of Winston presents the issue?

v3.8.1

What version of Node are you using?

v16.16.0

If this worked in a previous version of Winston, which was it?

No response

Minimum Working Example

import * as winston from 'winston'

class LogService extends winston.Logger {
  private static instance: LogService

  constructor () {
    super({
      level: process.env.LOG_LEVEL ?? 'info',
      exitOnError: false,
      format: winston.format.combine(winston.format.timestamp(), winston.format.json()),
    })
  }

  static getInstance = (): LogService => {
    if (LogService.instance == null) { LogService.instance = new LogService() }
    return LogService.instance
  }
}

export default LogService

[jianzhou520]

same issue

[Faithfinder]

So, Logger is a class because of the latest version update - #2157
However, it's simply not exported from https://github.com/winstonjs/winston/blob/master/lib/winston.js

There's even a warning that it's not allowed:

winston/lib/winston.js

Lines 175 to 176 in acaa95b

	// Throw a useful error when users attempt to run `new winston.Logger`.
	warn.moved(exports, 'createLogger', 'Logger');

Personally, I would like to extend the Logger as well. My purpose is providing default messages for common situations, for example:

    logEntityDeleted = (entity: EntityLike, additionalMetadata?: Record<string, unknown>): void => {
        this.log({
            level: 'audit',
            message: `${entityToString(entity)}, was deleted`,
            eventType: 'deleteEntity',
            entity: entity.constructor.name,
            entityId: entity.id,
            entityName: entity?.name,
            ...additionalMetadata,
        });
    };

I think the fix is as simple as exporting the Logger class, though that warning shows that it's not exported intentionally.

[ludgerey]

Having a similar issue with Transport. Is this related?

class WinstonEventEmitterTransport extends Transport {
                                           ^
TypeError: Class extends value undefined is not a constructor or null

Update: Fixed it by setting "esModuleInterop": true" in tsconfig.json.

[mikebarr24]

Having a similar issue with Transport. Is this related?

class WinstonEventEmitterTransport extends Transport {
                                           ^
TypeError: Class extends value undefined is not a constructor or null

Not sure if I've understood correctly but I am able to extend from Transport class using the 'winston-transport' module.

[ludgerey]

Having a similar issue with Transport. Is this related?

class WinstonEventEmitterTransport extends Transport {
                                           ^
TypeError: Class extends value undefined is not a constructor or null

Not sure if I've understood correctly but I am able to extend from Transport class using the 'winston-transport' module.

I got my specific problem fixed by by setting "esModuleInterop": true" in tsconfig.json. Sorry for the late update.

[marc-wilson]

+1

[DABH]

This should be solved via #2181 and will go out in the next release