Fix race in IntegrationTestingTutorial. (#594)

core/src/main/kotlin/net/corda/core/Utils.kt

@@ -275,11 +275,7 @@ class TransientProperty<out T>(private val initializer: () -> T) {
     @Transient private var v: T? = null
 
     @Synchronized
-    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
-        if (v == null)
-            v = initializer()
-        return v!!
-    }
+    operator fun getValue(thisRef: Any?, property: KProperty<*>) = v ?: initializer().also { v = it }
 }
 
 /**

core/src/main/kotlin/net/corda/core/utilities/Logging.kt

@@ -65,7 +65,7 @@ object LogHelper {
     /**
      * May fail to restore the original level due to unavoidable race if called by multiple threads.
      */
-    inline fun <T> withLevel(logName: String, levelName: String, block: () -> T) = let {
+    inline fun <T> withLevel(logName: String, levelName: String, block: () -> T) = run {
         val level = Level.valueOf(levelName)
         val oldLevel = LogManager.getLogger(logName).level
         Configurator.setLevel(logName, level)

docs/source/example-code/src/integration-test/kotlin/net/corda/docs/IntegrationTestingTutorial.kt

@@ -60,7 +60,7 @@ class IntegrationTestingTutorial {
             // START 4
             val issueRef = OpaqueBytes.of(0)
             val futures = Stack<ListenableFuture<*>>()
-            for (i in 1 .. 10) {
+            (1..10).map { i ->
                 thread {
                     futures.push(aliceProxy.startFlow(::CashIssueFlow,
                             i.DOLLARS,
@@ -69,14 +69,12 @@ class IntegrationTestingTutorial {
                             notary.nodeInfo.notaryIdentity
                     ).returnValue)
                 }
-            }
-            while (!futures.empty()) {
-                futures.pop().getOrThrow()
-            }
+            }.forEach(Thread::join) // Ensure the stack of futures is populated.
+            futures.forEach { it.getOrThrow() }
 
             bobVaultUpdates.expectEvents {
                 parallel(
-                        (1 .. 10).map { i ->
+                        (1..10).map { i ->
                             expect(
                                     match = { update: Vault.Update ->
                                         (update.produced.first().state.data as Cash.State).amount.quantity == i * 100L
@@ -90,13 +88,13 @@ class IntegrationTestingTutorial {
             // END 4
 
             // START 5
-            for (i in 1 .. 10) {
+            for (i in 1..10) {
                 bobProxy.startFlow(::CashPaymentFlow, i.DOLLARS, alice.nodeInfo.legalIdentity).returnValue.getOrThrow()
             }
 
             aliceVaultUpdates.expectEvents {
                 sequence(
-                        (1 .. 10).map { i ->
+                        (1..10).map { i ->
                             expect { update: Vault.Update ->
                                 println("Alice got vault update of $update")
                                 assertEquals((update.produced.first().state.data as Cash.State).amount.quantity, i * 100L)

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

@@ -87,13 +87,8 @@ class FlowStateMachineImpl<R>(override val id: StateMachineRunId,
 
     @Transient private var _resultFuture: SettableFuture<R>? = SettableFuture.create<R>()
     /** This future will complete when the call method returns. */
-    override val resultFuture: ListenableFuture<R> get() {
-        return _resultFuture ?: run {
-            val f = SettableFuture.create<R>()
-            _resultFuture = f
-            return f
-        }
-    }
+    override val resultFuture: ListenableFuture<R>
+        get() = _resultFuture ?: SettableFuture.create<R>().also { _resultFuture = it }
 
     // This state IS serialised, as we need it to know what the fiber is waiting for.
     internal val openSessions = HashMap<Pair<FlowLogic<*>, Party>, FlowSession>()
@@ -456,7 +451,7 @@ private data class FlowHandleImpl<A>(
 }
 
 @CordaSerializable
-private data class FlowProgressHandleImpl<A> (
+private data class FlowProgressHandleImpl<A>(
         override val id: StateMachineRunId,
         override val returnValue: ListenableFuture<A>,
         override val progress: Observable<String>) : FlowProgressHandle<A> {