feat(firestore): add addCollectionGroupSnapshotListener

[svrznjak]

Plugin(s)

• Analytics
• App
• App Check
• Authentication
• Crashlytics
• Cloud Firestore
• Cloud Messaging
• Cloud Storage
• Performance
• Remote Config

Current problem

I am not sure but I think there is a very important feature missing. What I am trying to do is addCollectionSnapshotListener on collectionGroup query.
Such a thing can be done with javascript firebase library like this:
const resources = query(collectionGroup(getFirestore(), 'resources'));
onSnapshot(resources, (querySnapshot) => {
querySnapshot.forEach((doc) => {
console.log(doc.data());
});
});

Preferred solution

Since there already are getCollection, addCollectionSnapshotListener and getCollectionGroup functions in API, I would suggest addCollectionGroupSnapshotListener function is added.

I made a quick glance at addCollectionSnapshotListener web code and I think whole function can be copied and only change that is needed is on line 212 where 'collecion' should be changed to 'collectionGroup'.

Alternative options

No response

Additional context

No response

Before submitting

• I have read and followed the feature request guidelines.
• I have attached links to possibly related issues and discussions.

[robingenz]

Thank you for your request. Would you be willing to create a PR?