Log caller function name and line number

[httpdigest]

There does not seem to be a way to log the caller's method name and line number. I know that this has already been requested with #200, but that issue was locked with the reason that such a function would be very slow. Given that a typical application would not excessively log thousands of log statements per second, it does not make a noticeably difference.

As you probably know, JavaScript provides the stack trace in the Error.stack property on construction of a new Error object. However, this is an unstructured string and needs to be parsed.
V8 on the other hand has a feature allowing to retrieve the stack trace in its original structured form (before stringifying). This is described here: https://github.com/v8/v8/wiki/Stack-Trace-API

My current implementation on top of Winston looks like this. (It may not be a good implementation, I'm very new to JavaScript and Node/V8. :) )

// ES2015
const path = require('path');
const winston = require('winston');
function CustomError() {
  // Use V8's feature to get a structured stack trace
  const oldStackTrace = Error.prepareStackTrace;
  const oldLimit = Error.stackTraceLimit;
  try {
    Error.stackTraceLimit = 3; // <- we only need the top 3
    Error.prepareStackTrace = (err, structuredStackTrace) => structuredStackTrace;
    Error.captureStackTrace(this, CustomError);
    this.stack; // <- invoke the getter for 'stack'
  } finally {
    Error.stackTraceLimit = oldLimit;
    Error.prepareStackTrace = oldStackTrace;
  }
}
function getAndFormatStackTraceElement() {
  const stack = new CustomError().stack;
  const CALLER_INDEX = 2; // <- position in stacktrace to find deepest caller
  const element = stack[CALLER_INDEX];
  const fileName = path.basename(element.getFileName());
  return element.getFunctionName() + "(" + fileName + ":" + element.getLineNumber() + ")";
}
module.exports = {
  info(msg, ...vars) {
    winston.info(getAndFormatStackTraceElement() + ': ' + msg, ...vars);
  }
}

Credits go to @addaleax from: nodejs/node#7749 (comment)
The way the string is formatted and the module exports are defined, sure needs reworking, I guess.

This ticket could serve as a discussion on how a good PR would look like for Winston, adding this feature to the library.

[hreimer]

hi, I am trying to use your wrapper right now and get this error:

RangeError: Maximum call stack size exceeded
    at CustomError.get stack [as stack] (native)
    at new CustomError (<filename:lineNumber>)
    at getAndFormatStackTraceElement (<filename:lineNumber>)
    at logger.error (<filename:lineNumber>)

Any idea how I could resolve this?
Did it happen to you too? thanks

[abumq]

Try Easylogging++ binding for node. See original library docs to check the potential of this binding

A simple example

const easyloggingpp = require('easyloggingpp');
const ConfigType = easyloggingpp.ConfigType;
const Level = easyloggingpp.Level;
const logger = easyloggingpp.getLogger('mylogger'); // register logger

easyloggingpp.configureAllLoggers([
    {
        config: ConfigType.Format,
        value: '%levshort %datetime %fbase:%line %msg',  // <-- fbase or file for full path 
    },
    {
        config: ConfigType.Filename,
        value: 'logs/output.log'
    }
]);

logger.info('simple log');
logger.info('array %s', [1, 2, 3]);
var person = { 'name': 'Adam', 'age': 960, }
logger.info('obj %s', person);

logger.error('an error occurred %s', new Error("error msg"));

easyloggingpp.setLogErrorStack(false); // turn stack logging off
logger.fatal('serious error occurred %s', new Error("fatal msg"));
logger.error('an error occurred %s', new Error("error msg"));

Sample output

[Shmee007]

hi, I am trying to use your wrapper right now and get this error:

RangeError: Maximum call stack size exceeded
    at CustomError.get stack [as stack] (native)
    at new CustomError (<filename:lineNumber>)
    at getAndFormatStackTraceElement (<filename:lineNumber>)
    at logger.error (<filename:lineNumber>)

Any idea how I could resolve this?
Did it happen to you too? thanks

In the line
Error.captureStackTrace(this, CustomError)
CustomError is effectively calling itself, so infinite loop and max call stack exceeded.

[Shmee007]

I used @httpdigest solution to create a Static class for what I needed but you can use it as above with winston
usage

const StackElements = require('./stackElements');
consol.log(StackElements.getFormatedStackTraceElement(1)); // 0 for current level, 1 for parent ...

export

const path = require('path');

class V8StackElements {
    static get stack() {
        return this.customStack;
    }

    constructor(callerIndex) {

        // Use V8's feature to get a structured stack trace
        const oldStackTrace = Error.prepareStackTrace;
        const oldLimit = Error.stackTraceLimit;
        try {
            Error.stackTraceLimit = callerIndex + 1; // <- we only want the top couple of elements
            Error.prepareStackTrace = (err, structuredStackTrace) => structuredStackTrace;
            Error.captureStackTrace(this);
            this.customStack = this.stack; // <- invoke the getter for 'stack'
        } finally {
            Error.stackTraceLimit = oldLimit;
            Error.prepareStackTrace = oldStackTrace;
        }
    }
}

class StackElements {
    static getFormatedStackTraceElement(callerIndex) {
        callerIndex = callerIndex + 2; //ignor v8 level and this level
        const stack = new V8StackElements(callerIndex).stack;
        const element = stack[callerIndex];
        const fileName = path.basename(element.getFileName());
        return element.getFunctionName() + "(" + fileName + ":" + element.getLineNumber() + ")";
    }
}

module.exports = StackElements;

I split it to 2 classes to only expose the intended function on the static class

I ended up here as I got stuck with the

'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them

when trying to use Function.caller

[indexzero]

Thanks for the suggestion @httpdigest! But as you said this is a duplicate of #200, so going to close it. Will leave the issue unlocked to keep the discussion going this time.

[yeongjet]

please provide a option to enable this feature, like log4js