minor cleanup

Author: dconeybe

firebase-dataconnect/src/main/kotlin/com/google/firebase/dataconnect/core/FirebaseDataConnectImpl.kt

@@ -421,27 +421,28 @@ internal class FirebaseDataConnectImpl(
       }
     }
 
-    // Register the new "close job", unless there is a "close job" already in progress or one that
-    // completed successfully.
-    val updatedCloseJob =
-      closeJob.updateAndGet { oldCloseJob ->
-        if (oldCloseJob.ref !== null && !oldCloseJob.ref.isCancelled) {
-          oldCloseJob
+    // Register the new "close job". Do not overwrite a close job that is already in progress (to
+    // avoid having more than one close job in progress at a time) or a close job that completed
+    // successfully (since there is nothing to do if a previous close job was successful).
+    val updatedCloseJobRef =
+      closeJob.updateAndGet { oldCloseJobRef: NullableReference<Deferred<Unit>> ->
+        if (oldCloseJobRef.ref !== null && !oldCloseJobRef.ref.isCancelled) {
+          oldCloseJobRef
         } else {
           NullableReference(newCloseJob)
         }
       }
 
-    // If the updated "close job" was the one that we created, then start it!
-    if (updatedCloseJob.ref === newCloseJob) {
-      newCloseJob.start()
-    }
+    // Start the updated "close job" (if it was already started then start() is a no-op).
+    val updatedCloseJob =
+      checkNotNull(updatedCloseJobRef.ref) {
+        "internal error: closeJob.updateAndGet() returned a NullableReference whose 'ref' " +
+          "property was null; however it should NOT have been null (error code y5fk4ntdnd)"
+      }
+    updatedCloseJob.start()
 
-    // Return the job "close job" that is active or already completed so that the caller can await
-    // its result.
-    return checkNotNull(updatedCloseJob.ref) {
-      "updatedCloseJob.ref should not have been null (error code y5fk4ntdnd)"
-    }
+    // Return the "close job", which _may_ already be completed, so the caller can await it.
+    return updatedCloseJob
   }
 
   // The generated SDK relies on equals() and hashCode() using object identity.