Bluebird 3.x performance in webpack

This issue seems totally bizarre to me. I’m not sure whether to file it under webpack or Bluebird, but since it may be affecting other bluebird users I’ll file it here.

I’ve been finding that Bluebird’s performance in the browser has been pretty shoddy since I upgraded to bluebird 3.

In an effort to diagnose the problem, I started conducting some tests here: https://github.com/suprememoocow/bluebird-webpack-perf

The results are strange to say the least, but here’s some of what I’m seeing:

• A simple Promise.reduce with an array of 100 values takes 2ms when run in Chrome 64bit on OSX. The exact same code, when processed through webpack takes 500ms.
• You can compare the implementations here: https://github.com/suprememoocow/bluebird-webpack-perf/blob/master/bluebird-no-webpack.html and https://github.com/suprememoocow/bluebird-webpack-perf/blob/master/bluebird-with-webpack.js
• In an effort to isolate the problem, I’ve minimized the processing that webpack does with the following settings:

      module: {
        noParse: [
          /bluebird\/js\/browser\/bluebird\.js/
        ]
      },
      node: {
        console: false,
        global: false,
        process: false,
        Buffer: false,
        __filename: false,
        __dirname: false,
        setImmediate: false
      },

• Changing these settings hasn’t helped.
• Downgrading to Bluebird 2.x.x fixes the problem.

I’ll conduct some further tests and see if I can get to the bottom of the problem

[suprememoocow]

Doing some profiling I noticed that bluebird is capturing long stack traces even though I have

Promise.config({
    warnings: false,
    longStackTraces: false, // <-- Turn off long stack traces
    cancellation: true
  });

This would explain why Chrome is getting the performance hit, but not Firefox or Safari.

Upon further investigation, it looks like the __DEBUG__ constant is being set to true for the build of js/browser/bluebird.js if you compare:

js/browser/bluebird.js:658:var debugging =!!(true || util.env("BLUEBIRD_DEBUG") ||

to the original source, here: https://github.com/petkaantonov/bluebird/blob/master/src/debuggability.js#L18

[suprememoocow]

@petkaantonov, I am using the npm module, which references js/browser/browser.js, which is currently built with __DEBUG__ set to true. #898 is my attempt at changing this.

References: require('bluebird') package.json