ThenableReference returning PromiseLike - should be Promise?

[stevejcox]

It looks like when the RTDB were put back in with pr: #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 ?

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[hiranya911]

PromiseLike is what is used in JS SDK, where the RTDB code actually resides.

@jshcrowthe wdyt?

[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?

[jshcrowthe]

I am probably the wrong guy for the "why?" question here. I'll reassign to @schmidt-sebastian who can probably give us a better clue of what is going on.

[ezos86]

@stevejcox
I notice this too. If I push a null value into a location. I don't get a .catch(function(error)} - even though firebase couldn't make the insert into the DB. in the browser, it would return a console error, but the node SDK just treats the .then not a .catch.

[pontius-g]

When we use .catch() for .push() - SDK tells we're wrong!
When we don't - debugger tells - we didn't .catch() an error from Promise!
Think, it's better for push() to become a promise...
Or please, offer more elegant suggestion.

[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.

[pontius-g]

Thanks a lot, my bad to not following a reference.
I'll try your solution instead of "temporary .push() replacement" - .set(this.db.createPushId(), data)