ThenableReference returning PromiseLike - should be Promise?

It looks like when the RTDB were put back in with pr: https://github.com/firebase/firebase-admin-node/pull/140 the interface of ThenableReference changed form extending Promise<any> to PromiseLike<any>.

Is there a reason for this?

PromiseLike does not include a catch declaration for typescript - and so is causing an error. I believe this should be Promise<any> ?

[schmidt-sebastian]

The ES6 type definition for PromiseLike is as follows:

interface PromiseLike<T> {
    /**
     * Attaches callbacks for the resolution and/or rejection of the Promise.
     * @param onfulfilled The callback to execute when the Promise is resolved.
     * @param onrejected The callback to execute when the Promise is rejected.
     * @returns A Promise for the completion of which ever callback is executed.
     */
    then<TResult1 = T, TResult2 = never>(onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | undefined | null, onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null): PromiseLike<TResult1 | TResult2>;
}

This is a little hard to read, but it basically states that you can register an error callback as the second argument to your .then() callback. You can try something like this:

.push({...}).then(onsuccess, onfailure)

Note that the RTDB JS SDK uses PromiseLike in some cases to keep backwards compatibility.

[stevejcox]

Just following up on this, @jshcrowthe - push() seems to return a ThenableReference rather than a Promise. Is there a reason for this? ThenableReference doesn’t have declarations for catch, so not totally sure why it wouldn’t be a Promise too?