Disposer does not cleanup after rejection

Good day everyone,

today I encountered an issue with the Disposer object which looked pretty nice at first glance but seems to be a tricky to use.

First things first:

• Bluebird version: 3.5.0
• Platform: Windows 7 (x64)
• Node version: 4.4.3

“Did this issue happen with earlier versions of bluebird”? I am not sure. First I thought it worked with 3.3.5 but that was not the case.

The issue

Alright, I might not use the correct approach to use Disposers and Promise.using so please let me know when I failed that regard - if I didn’t mess up it might be my understanding of Disposers and resources in general; Again, please let me know.

Code explains better than my linguistic skills would allow:

'use strict';

const Promise = require('bluebird');

function eww() {
  return Promise.reject(new Error('evil issue'))
    .delay(100)
    .disposer(() => {
      console.log('should be called but never is');
    });
}

Promise.using(eww(), () => {
  console.log('positive case - never called');
})
.catch((err) => {
  console.log('failed as expected - resource is not cleaned up.');
})

The basic issue is that my disposer function is never called which should be a Bluebird issue. The reason being - again, my understanding - that whenever I attempt to claim a resource, the disposer always takes care about the proper cleanup.

Currently, when my resource claiming function (eww() from the example) fails, I have to manually clean up my mess - which may is impossible when I wrap my code behind the disposer.

The problem is this code chunk.

The issue is not to be mistaken with this issue. I suspect it never worked like I thought it would…

Can anyone confirm this behavior? I wonder if this is intended. If I have to manually clean up after disposers, I rather not use them at all. The caller should not care about cleaning up in such cases - especially in rejection cases.

Edit: I changed the code within the using.js to the following (resource method):

Disposer.prototype.resource = function () {
        if (this.promise().isFulfilled()) {
            return this.promise().value();
        }
        if (this.promise().isRejected()) {
            return this.promise().reason();
        }
        return NULL;
    };

This causes the disposer to work as intended. If this is a proper change to you, let me know and I’ll PR you it.

Best regards, Philipp

[petkaantonov]

Disposer cannot be called because there is nothing to call it with.

[ptusch]

@benjamingr Ahh, I just read your comment there. I didn’t know that a .disposer function requires to guarantee no throw.

Thanks for the link!