IllegalArgumentException thrown when List<Deferred<T>>.awaitAll() is used on List<TransactionResult<T>>

[emanguy]

Assume augmentItem(item) is just a private function which executes 3 queries across various tables and I have nested transactions enabled on the DB.

If I do:

newSuspendedTransaction(Dispatchers.IO) {
  val listOfItems = /* Transaction extension, invokes suspendedTransaction and does a query */
  val results = listOfItems.suspendedTransactionAsync { augmentItem(item) }.awaitAll()
}

It will fail on the awaitAll, saying the transaction is already closed.

On the other hand, the following works:

newSuspendedTransaction(Dispatchers.IO) {
  val listOfItems = /* Transaction extension, invokes suspendedTransaction and does a query */
  val results = listOfItems.suspendedTransactionAsync { augmentItem(item) }.map { it.await() }
}

I'm 99% certain this is a bug given TransactionResult inherits from Deferred. This occurs on Exposed 1.17.6.

[Tapac]

I'm 99% certain this is a bug given TransactionResult inherits from Deferred.

You are right. After some debug I faced that only inheritors of async could work normally with awaitAll while TransactionResult just delegates to async.

I thinking about remove TransactionResult and just use a simple async instead. What do you think?

[emanguy]

Yeah, that seems to be a good way to move forward. Let me know if I can do anything to help.