Swagger的Bluebird Promise：return不是函数

Question

I'm using Swagger to create my JS API client for calling a set of REST endpoints. I'm configuring the Swagger client to use Promises ( new Swagger({ spec: spec, usePromise: true }) ).

I require Bluebird before Swagger, to use Bluebird promises. But my app is blowing up when trying to use Promise.return .

The code looks like

client.user.get_db_user(db).return("foo");

where client is the Swagger reference.

The error I get is

app: TypeError: client.user.get_db_user(...).return is not a function

It works if I replace return with then(() => value) . return is supposed to be shorthand for this sort of use of then .

After investigating, I see it's failing on promises returned by the Swagger client.

What's happening?

Answer 1

It doesn't appear that you can tell Swagger to use Bluebird promises. But, in specific places where you want to use Bluebird's methods, you can "cast" a Swagger promise to a Bluebird promise and then use Bluebird's features. To convert a promise like that, you just wrap it in Promise.resolve() :

const Promise = require('bluebird');

Promise.resolve(client.user.get_db_user(db)).return(...)

Although in this specific case, since .return() is just there to save you some typing, it isn't really a net savings after you've wrapped the previous promise in Promise.resolve() . But, for more meaningful methods like .map() or something like that, it might be more useful.

Answer 2

It turns out that Swagger uses the Q promise library explicitly under the hood.

Bluebird and Q are partially compatible, so many things work fine. The problem happens when trying to use parts of the Bluebird API that Q doesn't have.

In particular, Bluebird has "return", whereas Q does not.

The easiest answer is to use the then construction discussed in the question.

Other possible solutions I have yet to try:

1. Use the "bluebird-q" project to replace Q with Bluebird.
2. promisifyAll Swagger instead of using Swagger's built-in promise support.