allow user to pick a promise lib

[jchip]

Having this module explicitly depend on Q is an inconvenience when user doesn't want to use Q. The browser version also packs a copy of Q, even if we don't want to use Promise or want to use another Promise polyfill.

Would you consider removing explicit dependence on any specific Promise implementation, and allow user to supply a polyfill?

Some ideas:

• expose a swaggerClient.Promise that user can set but assign global Promise to it by default.
• If Promise is not defined, then throw error if usePromise is true.

Q.defer can be implemented using the ES6 Promise:

function defer() {
  var deferred = {};
  deferred.promise = new Promise(function (resolve, reject) {
    deferred.resolve = resolve;
    deferred.reject = reject;
  });

  return deferred;
};

This change would require a major version bump.

[fehguy]

We're working on this for the next version.

[mbana]

Thanks. Would be nice to use this https://github.com/stefanpenner/es6-promise.

[sebinsua]

The best way of doing this is with: any-promise

[fehguy]

This has been done in the 3.x version.