Fix types for Object Listener (#4338)

When a class extends Realm.Object, adding a listener to an instance of the
object would not correctly type the object returned in the callback.
With this change, the callback returns an object of the same type as the
instance it was called from.

.gitignore-revs

@@ -1,3 +1,4 @@
 c76131748cbb048e78a987eb234d8a9609e26430
 f38d8cf7cac992767a451d2f3cf3310e3546bf6f
 fa80f12bf3fbfe1337ae69e12c59051fac347001
+99e64a8e990d2579bcfe382f755edbc61f70af4e

packages/realm-react/src/useObject.tsx

@@ -28,15 +28,21 @@ export function createUseObject(useRealm: () => Realm) {
     );
 
     useEffect(() => {
-      const listenerCallback: Realm.ObjectChangeCallback = (_, changes) => {
+      const listenerCallback: Realm.ObjectChangeCallback<T & Realm.Object> = (_, changes) => {
         if (changes.changedProperties.length > 0) {
           setObject(() => realm.objectForPrimaryKey(type, primaryKey) ?? null);
         } else if (changes.deleted) {
           setObject(null);
         }
       };
-      object?.addListener(listenerCallback);
-      return () => object?.removeListener(listenerCallback);
+      if (object !== null) {
+        object.addListener(listenerCallback);
+      }
+      return () => {
+        if (object !== null) {
+          object.removeListener(listenerCallback);
+        }
+      };
     }, [realm, object, type, primaryKey]);
 
     return object;

types/index.d.ts

@@ -199,12 +199,12 @@ declare namespace Realm {
         [keys: string]: any;
     }
 
-    interface ObjectChangeSet {
+    interface ObjectChangeSet<T> {
         deleted: boolean;
-        changedProperties: string[]
+        changedProperties: (keyof T)[]
     }
 
-    type ObjectChangeCallback = (object: Object, changes: ObjectChangeSet) => void;
+    type ObjectChangeCallback<T> = (object: T, changes: ObjectChangeSet<T>) => void;
 
     /**
      * Object
@@ -251,16 +251,16 @@ declare namespace Realm {
         /**
          * @returns void
          */
-        addListener(callback: ObjectChangeCallback): void;
+        addListener(callback: ObjectChangeCallback<this>): void;
 
-        removeListener(callback: ObjectChangeCallback): void;
+        removeListener(callback: ObjectChangeCallback<this>): void;
 
         removeAllListeners(): void;
 
         /**
          * @returns string
          */
-        getPropertyType(propertyName: string) : string;
+        getPropertyType(propertyName: string): string;
     }
 
     /**