What is the correct way of using Bluebird for Mongoose promises?

Choose the Mongoose way:

mongoose.Promise = require('bluebird');

That's because Mongoose already supports promises (besides also accepting callbacks); the above code just replaces Mongoose's own promise library (mpromise) by Bluebird (which is probably faster, better tested, and has more utility functions available).

Bluebird's promisify*() is meant to allow code that doesn't already use promises (purely callback-based functions) to return promises.

From Bluebird doc

Promise.promisifyAll(    Object target,    [Object {        suffix: String="Async",        multiArgs: boolean=false,        filter: boolean function(String name, function func, Object target, boolean passesDefaultFilter),        promisifier: function(function originalFunction, function defaultPromisifier)    } options] ) -> Object

as you can see, by default, promisifyAll add suffix 'Asyns', so if you are using this way of promisification:

var Promise = require("bluebird");Promise.promisifyAll(require("mongoose"));

the async version of User.findById will be User.findByIdAsync

what about mongoose.Promise

then you use promise library like

mongoose.Promise = require('bluebird');

built-in promise mechanism replaced by library: query.exec().constructor replaced by require('bluebird') so instead .exec() for return promise, you can use bluebird probabilities directly for mongoose queries like

User.findOne({}).then(function(user){    // ..})  

For those of you using TypeScript, the correct way is:

(<any>mongoose).Promise = YOUR_PROMISE;

From the documentation:

Typescript does not allow assigning properties of imported modules. To avoid compile errors use one of the options below in your code:(<any>mongoose).Promise = YOUR_PROMISE;require('mongoose').Promise = YOUR_PROMISE;import mongoose = require('mongoose'); mongoose.Promise = YOUR_PROMISE;