Inconsistent behavior of execution when using multiple copies of bluebird

1. What version of bluebird is the issue happening on?

v3.5.1

1. What platform and version? (For example Node.js 0.12 or Google Chrome 32)

Node.js 6.8.1 & Node.js 8.11.1

1. Did this issue happen with earlier version of bluebird?

It also happens with bluebird v3.4.7

To replicate:

1. mkdir bluebird-test
2. cd bluebird-test
3. npm init --yes
4. npm i bluebird --save
5. cp -r ./node_modules/bluebird ./node_modules/bluebird2
6. touch index.js
7. copy & paste the following into the index.js
8. node index.js

const Promise = require('bluebird');
const Promise2 = require('bluebird2');

function second() {
    console.log('SECOND');
}

function start() {
    return new Promise(function(resolve, reject) {

        process.nextTick(tick);

        function tick() {
            return setup().catch(function(err) {
                console.log('FIRST');
            });
        }
    });
}

function setup() {
    return Promise.resolve().then(function() {
        //Promise2 executes/is handled differently
        return Promise2.map([1], function() {
            process.nextTick(function() {
                second();
            });
            throw new Error('test error');
        });
    });
}

return start();

stdout:

SECOND
FIRST

expected stdout:

FIRST
SECOND

When only a single bluebird package is used as in the script bellow, I get the expected output;

const Promise = require('bluebird');

function second() {
    console.log('SECOND');
}

function start() {
    return new Promise(function(resolve, reject) {

        process.nextTick(tick);

        function tick() {
            return setup().catch(function(err) {
                console.log('FIRST');
            });
        }
    });
}

function setup() {
    return Promise.resolve().then(function() {
        return Promise.map([1], function() {
            process.nextTick(function() {
                second();
            });
            throw new Error('test error');
        });
    });
}

return start();

This is the case when some dependent npm package requires different version of bluebird or simply project’s dependencies are not flatten out. Understandably this breaks things.

Despite that, Thank you for the amazing library!

[benjamingr]

What’s the implementation reason behind NOT returning the original promise object for object that isAnyBluebirdPromise as it is done:

It might be a different version of bluebird and not contain the same methods - for example Bluebird 2 and Bluebird 3.

[fogine]

Bluebird instances identify each other and do a performance optimization where they don’t need to do the whole ResolveThenableJob dance they need to with native promises.

What’s the implementation reason behind NOT returning the original promise object for object that isAnyBluebirdPromise as it is done: https://github.com/petkaantonov/bluebird/blob/49da1ac256c7ee0fb1e07679791399f24648b933/src/thenables.js#L10