ENT-6142 Use ArrayList for SessionState structures (#4169)

Prevent some serialization errors that occur due to serialization
and deserialization of `ArrayList$SubList` found inside the
`SessionState` data structures.

To prevent this, an explicit `ArrayList` is used rather than a `List`.

Overload the `List` operator functions so that `+` returns an
`ArrayList` instead of a `List`.

Create `toArrayList` for a few conversions.

node/src/main/kotlin/net/corda/node/services/statemachine/StateMachineState.kt

@@ -281,7 +281,7 @@ sealed class SessionState {
      * @property rejectionError if non-null the initiation failed.
      */
     data class Initiating(
-            val bufferedMessages: List<Pair<DeduplicationId, ExistingSessionMessagePayload>>,
+            val bufferedMessages: ArrayList<Pair<DeduplicationId, ExistingSessionMessagePayload>>,
             val rejectionError: FlowError?,
             override val deduplicationSeed: String
     ) : SessionState()
@@ -298,7 +298,7 @@ sealed class SessionState {
     data class Initiated(
             val peerParty: Party,
             val peerFlowInfo: FlowInfo,
-            val receivedMessages: List<ExistingSessionMessagePayload>,
+            val receivedMessages: ArrayList<ExistingSessionMessagePayload>,
             val otherSideErrored: Boolean,
             val peerSinkSessionId: SessionId,
             override val deduplicationSeed: String

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/DeliverSessionMessageTransition.kt

@@ -87,7 +87,7 @@ class DeliverSessionMessageTransition(
                 val initiatedSession = SessionState.Initiated(
                         peerParty = event.sender,
                         peerFlowInfo = message.initiatedFlowInfo,
-                        receivedMessages = emptyList(),
+                        receivedMessages = arrayListOf(),
                         peerSinkSessionId = message.initiatedSessionId,
                         deduplicationSeed = sessionState.deduplicationSeed,
                         otherSideErrored = false

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/ErrorFlowTransition.kt

@@ -121,9 +121,9 @@ class ErrorFlowTransition(
             if (sessionState is SessionState.Initiating && sessionState.rejectionError == null) {
                 // *prepend* the error messages in order to error the other sessions ASAP. The other messages will
                 // be delivered all the same, they just won't trigger flow resumption because of dirtiness.
-                val errorMessagesWithDeduplication = errorMessages.map {
+                val errorMessagesWithDeduplication: ArrayList<Pair<DeduplicationId, ExistingSessionMessagePayload>> = errorMessages.map {
                     DeduplicationId.createForError(it.errorId, sourceSessionId) to it
-                }
+                }.toArrayList()
                 sessionState.copy(bufferedMessages = errorMessagesWithDeduplication + sessionState.bufferedMessages)
             } else {
                 sessionState

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/KilledFlowTransition.kt

@@ -7,12 +7,14 @@ import net.corda.node.services.statemachine.Checkpoint
 import net.corda.node.services.statemachine.DeduplicationId
 import net.corda.node.services.statemachine.ErrorSessionMessage
 import net.corda.node.services.statemachine.Event
+import net.corda.node.services.statemachine.ExistingSessionMessagePayload
 import net.corda.node.services.statemachine.FlowError
 import net.corda.node.services.statemachine.FlowRemovalReason
 import net.corda.node.services.statemachine.FlowState
 import net.corda.node.services.statemachine.SessionId
 import net.corda.node.services.statemachine.SessionState
 import net.corda.node.services.statemachine.StateMachineState
+import java.util.ArrayList
 
 class KilledFlowTransition(
     override val context: TransitionContext,
@@ -101,9 +103,9 @@ class KilledFlowTransition(
             if (sessionState is SessionState.Initiating && sessionState.rejectionError == null) {
                 // *prepend* the error messages in order to error the other sessions ASAP. The other messages will
                 // be delivered all the same, they just won't trigger flow resumption because of dirtiness.
-                val errorMessagesWithDeduplication = errorMessages.map {
+                val errorMessagesWithDeduplication: ArrayList<Pair<DeduplicationId, ExistingSessionMessagePayload>> = errorMessages.map {
                     DeduplicationId.createForError(it.errorId, sourceSessionId) to it
-                }
+                }.toArrayList()
                 sessionState.copy(bufferedMessages = errorMessagesWithDeduplication + sessionState.bufferedMessages)
             } else {
                 sessionState

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/StartedFlowTransition.kt

@@ -250,7 +250,7 @@ class StartedFlowTransition(
                     if (messages.isEmpty()) {
                         someNotFound = true
                     } else {
-                        newSessionMessages[sessionId] = sessionState.copy(receivedMessages = messages.subList(1, messages.size).toList())
+                        newSessionMessages[sessionId] = sessionState.copy(receivedMessages = messages.subList(1, messages.size).toArrayList())
                         // at this point, we've already checked for errors and session ends, so it's guaranteed that the first message will be a data message.
                         resultMessages[sessionId] = if (messages[0] is EndSessionMessage) {
                             throw UnexpectedFlowEndException("Received session end message instead of a data session message. Mismatched send and receive?")
@@ -285,7 +285,7 @@ class StartedFlowTransition(
             }
             val initialMessage = createInitialSessionMessage(sessionState.initiatingSubFlow, sourceSessionId, sessionState.additionalEntropy, null)
             val newSessionState = SessionState.Initiating(
-                    bufferedMessages = emptyList(),
+                    bufferedMessages = arrayListOf(),
                     rejectionError = null,
                     deduplicationSeed = sessionState.deduplicationSeed
             )
@@ -324,7 +324,7 @@ class StartedFlowTransition(
             val deduplicationId = DeduplicationId.createForNormal(checkpoint, index++, sessionState)
             val initialMessage = createInitialSessionMessage(uninitiatedSessionState.initiatingSubFlow, sourceSessionId, uninitiatedSessionState.additionalEntropy, message)
             newSessions[sourceSessionId] = SessionState.Initiating(
-                    bufferedMessages = emptyList(),
+                    bufferedMessages = arrayListOf(),
                     rejectionError = null,
                     deduplicationSeed = uninitiatedSessionState.deduplicationSeed
             )
@@ -375,7 +375,10 @@ class StartedFlowTransition(
                             if (sessionState.receivedMessages.isNotEmpty() && sessionState.receivedMessages.first() is ErrorSessionMessage) {
                                 val errorMessage = sessionState.receivedMessages.first() as ErrorSessionMessage
                                 val exception = convertErrorMessageToException(errorMessage, sessionState.peerParty)
-                                val newSessionState = sessionState.copy(receivedMessages = sessionState.receivedMessages.subList(1, sessionState.receivedMessages.size), otherSideErrored = true)
+                                val newSessionState = sessionState.copy(
+                                    receivedMessages = sessionState.receivedMessages.subList(1, sessionState.receivedMessages.size).toArrayList(),
+                                    otherSideErrored = true
+                                )
                                 val newCheckpoint = startingState.checkpoint.addSession(sessionId to newSessionState)
                                 newState = startingState.copy(checkpoint = newCheckpoint)
                                 listOf(exception)

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/Transition.kt

@@ -24,6 +24,37 @@ interface Transition {
         val continuation = build(builder)
         return TransitionResult(builder.currentState, builder.actions, continuation)
     }
+
+    /**
+     * Add [element] to the [ArrayList] and return the list.
+     *
+     * Copy of [List.plus] that returns an [ArrayList] instead.
+     */
+    operator fun <T> ArrayList<T>.plus(element: T) : ArrayList<T> {
+        val result = ArrayList<T>(size + 1)
+        result.addAll(this)
+        result.add(element)
+        return result
+    }
+
+    /**
+     * Add [elements] to the [ArrayList] and return the list.
+     *
+     * Copy of [List.plus] that returns an [ArrayList] instead.
+     */
+    operator fun <T> ArrayList<T>.plus(elements: Collection<T>) : ArrayList<T> {
+        val result = ArrayList<T>(this.size + elements.size)
+        result.addAll(this)
+        result.addAll(elements)
+        return result
+    }
+
+    /**
+     * Convert the [List] into an [ArrayList].
+     */
+    fun <T> List<T>.toArrayList() : ArrayList<T> {
+        return ArrayList(this)
+    }
 }
 
 class TransitionContext(

node/src/main/kotlin/net/corda/node/services/statemachine/transitions/UnstartedFlowTransition.kt

@@ -6,6 +6,7 @@ import net.corda.node.services.statemachine.ConfirmSessionMessage
 import net.corda.node.services.statemachine.DataSessionMessage
 import net.corda.node.services.statemachine.DeduplicationId
 import net.corda.node.services.statemachine.ExistingSessionMessage
+import net.corda.node.services.statemachine.ExistingSessionMessagePayload
 import net.corda.node.services.statemachine.FlowStart
 import net.corda.node.services.statemachine.FlowState
 import net.corda.node.services.statemachine.SenderDeduplicationId
@@ -50,9 +51,9 @@ class UnstartedFlowTransition(
                         appName = initiatingMessage.appName
                 ),
                 receivedMessages = if (initiatingMessage.firstPayload == null) {
-                    emptyList()
+                    arrayListOf()
                 } else {
-                    listOf(DataSessionMessage(initiatingMessage.firstPayload))
+                    arrayListOf<ExistingSessionMessagePayload>(DataSessionMessage(initiatingMessage.firstPayload))
                 },
                 deduplicationSeed = "D-${initiatingMessage.initiatorSessionId.toLong}-${initiatingMessage.initiationEntropy}",
                 otherSideErrored = false