RN Partial Subscription missing addListener

[sambwest]

Background

I use realm on the server using Node and in React Native. On the server this issue doesn't happen, it is only in React native

Goals

Attach a listener to an object subscription

Expected Results

The listener is attached.

Actual Results

subscription.addListener is not a function. It does return an object, but it doesn't have any of the methods in the docs. The objects are subscribed to ok.

Steps to Reproduce

Try and add a listener to a object subscription in React Native

Code Sample

I'm actually using the listener function from your tests but the same thing happens using vanilla.

  subscribe (results) {
    const subscription = results.subscribe()
    return new Promise((resolve, reject) => {
      subscription.addListener((subscription, state) => {
        if (state === Realm.Sync.SubscriptionState.Complete) {
          resolve()
        }
        else if (state === Realm.Sync.SubscriptionState.Error) {
          reject()
        }
      })
      setTimeout(() => reject('listener never called'), 5000)
    })
  }

let objs = realm.objects('User');
await subscribe(objs);

Normal example

let objs = realm.objects('User');
let sub = objs.subscribe();
sub.addListener((subscription, state) => {
...
})

Version of Realm and Tooling

• Realm JS SDK Version: 2.8.3
• Node or React Native: 0.55.4
• Client OS & Version:
• Which debugger for React Native: Chrome

[kneth]

Just to clarify: subscribe() does not return an object which has methods like addListener()? And you only observe this with React Native?

[sambwest]

Exactly. Only in react native. The exact same code works in node. The documentation here says it should return a Realm.Sync.Subscription. (https://realm.io/docs/javascript/latest/api/Realm.Results.html#subscribe). See comment in code below.

let objs = realm.objects('User');
let sub = objs.subscribe();

// here typeof sub.addListener === 'undefined' 

sub.addListener((subscription, state) => {
...
})

[kneth]

I have started implemented what is needed in #1902 but I don't expect to finish it until late next week.