bluebird-co

A set of yield handlers for Bluebird coroutines.

Description

This is a port of tj/co generator coroutines to bluebird using Bluebird.addYieldHandler to add in a yield handler that can transform all the types of yieldable values tj/co can into normal promises to resolve.

Combined with Babel's bluebirdCoroutines transformer, you can write easy and comprehensive async/await functions.

Usage

require('bluebird-co') and done.

Usage in detail (to ensure everything works)

bluebird-co works by requiring bluebird and calling Bluebird.coroutine.addYieldHandler to add the appropriate functionality.

However, to ensure everything works you will need to install bluebird before any other module, so it exists in your node_modules folder. Then when you install any other module, including bluebird-co, they will require the already installed copy of bluebird instead of installing another, independent copy in their own node_modules folder.

Likewise, if you intend to override co.wrap, you will have to install co before any module that relies on co, that way koa and the like will use it instead of installing their own copy.

Your package.json should look something like this:

{
    "...": "...",
    "dependencies": {
        "bluebird":     "^2.9.33",
        "co":           "^4.5.4",
        "bluebird-co":  "^1.0.2"
    },
    "...": "..."
}

before installing any other module that relies on those.

#####NOTE: Before you delete your package.json out of frustration You can achieve the desired state of your node_modules by simply installing bluebird, co optionally, then bluebird-co, saving them to your package.json, then deleting your node_modules folder. Then run npm install, and it'll install your dependencies without duplicates.

Example coroutine

var Promise = require('bluebird');
var fs = Promise.promisifyAll(require('fs'));

var myAsyncFunction = Promise.coroutine(function*(){
    var results = yield [Promise.delay( 10 ).return( 42 ),
                         readFileAsync( 'index.js', 'utf-8' ),
                         [1, Promise.resolve( 12 )]];
    
    console.log(results); //[42, "somefile contents", [1, 12]]
});

myAsyncFunction().then(...);

ES7 version

import Promise from 'bluebird';
import {readFile} from 'fs';

let readFileAsync = Promise.promisify(readFile);

async function myAsyncFunction() {
    let results = await [Promise.delay( 10 ).return( 42 ),
                         readFileAsync( 'index.js', 'utf-8' ),
                         [1, Promise.resolve( 12 )]];
                         
    console.log(results); //[42, "somefile contents", [1, 12]]
}

myAsyncFunction().then(...);

For more examples, see the tj/co README and the Bluebird Coroutines API.

Overriding co.wrap

In my own experience, mixing bluebird coroutines and co/co.wrap can result in less than savory stack traces and other things. Here is a simple way to override almost all common usages of the co library.

var Promise = require('bluebird');
var co = require('co');

co.wrap = function(fn) {
    return Promise.coroutine(fn);
}

I've been using this method with Koa and a few other libraries for a while now and it seems to work. However, if a library invokes co directly, it will fail to replace that.

License

The MIT License (MIT)

Copyright (c) 2015 Aaron Trent

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.