Fix double spending of inputs issue on ledger level in test dsl. (#15)

* Fix double spending of inputs issue on ledger level in test dsl.

* Address PR comments.

core/src/main/kotlin/net/corda/core/contracts/TransactionVerification.kt

@@ -107,7 +107,6 @@ sealed class TransactionVerificationException(val tx: LedgerTransaction, cause:
         override val message: String?
             get() = "Missing required encumbrance ${missing} in ${inOut}"
     }
-
     enum class Direction {
         INPUT,
         OUTPUT

finance/src/test/kotlin/net/corda/contracts/asset/CashTests.kt

@@ -717,4 +717,39 @@ class CashTests {
         // Test that summing everything fails because we're mixing units
         states.sumCash()
     }
+
+    // Double spend.
+    @Test
+    fun chainCashDoubleSpendFailsWith() {
+        ledger {
+            unverifiedTransaction {
+                output("MEGA_CORP cash") {
+                    Cash.State(
+                            amount = 1000.DOLLARS `issued by` MEGA_CORP.ref(1, 1),
+                            owner = MEGA_CORP_PUBKEY
+                    )
+                }
+            }
+
+            transaction {
+                input("MEGA_CORP cash")
+                output("MEGA_CORP cash".output<Cash.State>().copy(owner = DUMMY_PUBKEY_1))
+                command(MEGA_CORP_PUBKEY) { Cash.Commands.Move() }
+                this.verifies()
+            }
+
+            tweak {
+                transaction {
+                    input("MEGA_CORP cash")
+                    // We send it to another pubkey so that the transaction is not identical to the previous one
+                    output("MEGA_CORP cash".output<Cash.State>().copy(owner = ALICE_PUBKEY))
+                    command(MEGA_CORP_PUBKEY) { Cash.Commands.Move() }
+                    this.verifies()
+                }
+                this.fails()
+            }
+
+            this.verifies()
+        }
+    }
 }

test-utils/src/main/kotlin/net/corda/testing/TestDSL.kt

@@ -79,6 +79,7 @@ sealed class EnforceVerifyOrFail {
 }
 
 class DuplicateOutputLabel(label: String) : Exception("Output label '$label' already used")
+class DoubleSpentInputs(ids: List<SecureHash>) : Exception("Transactions spend the same input. Conflicting transactions ids: '$ids'")
 class AttachmentResolutionException(attachmentId: SecureHash) : Exception("Attachment with id $attachmentId not found")
 
 /**
@@ -167,7 +168,7 @@ data class TestLedgerDSLInterpreter private constructor (
     companion object {
         private fun getCallerLocation(): String? {
             val stackTrace = Thread.currentThread().stackTrace
-            for (i in 1 .. stackTrace.size) {
+            for (i in 1..stackTrace.size) {
                 val stackTraceElement = stackTrace[i]
                 if (!stackTraceElement.fileName.contains("DSL")) {
                     return stackTraceElement.toString()
@@ -182,8 +183,10 @@ data class TestLedgerDSLInterpreter private constructor (
             val transaction: WireTransaction,
             val location: String?
     )
+
     class VerifiesFailed(transactionName: String, cause: Throwable) :
             Exception("Transaction ($transactionName) didn't verify: $cause", cause)
+
     class TypeMismatch(requested: Class<*>, actual: Class<*>) :
             Exception("Actual type $actual is not a subtype of requested type $requested")
 
@@ -249,7 +252,6 @@ data class TestLedgerDSLInterpreter private constructor (
             }
             labelToOutputStateAndRefs[label] = wireTransaction.outRef(index)
         }
-
         transactionMap[wireTransaction.id] =
                 WireTransactionWithLocation(transactionLabel, wireTransaction, transactionLocation)
 
@@ -279,10 +281,20 @@ data class TestLedgerDSLInterpreter private constructor (
 
     override fun verifies(): EnforceVerifyOrFail {
         try {
+            val usedInputs = mutableSetOf<StateRef>()
             services.recordTransactions(transactionsUnverified.map { SignedTransaction(it.serialized, listOf(NullSignature), it.id) })
             for ((key, value) in transactionWithLocations) {
-                value.transaction.toLedgerTransaction(services).verify()
-                services.recordTransactions(SignedTransaction(value.transaction.serialized, listOf(NullSignature), value.transaction.id))
+                val wtx = value.transaction
+                val ltx = wtx.toLedgerTransaction(services)
+                ltx.verify()
+                val doubleSpend = wtx.inputs.intersect(usedInputs)
+                if (!doubleSpend.isEmpty()) {
+                    val txIds = mutableListOf(wtx.id)
+                    doubleSpend.mapTo(txIds) { it.txhash }
+                    throw DoubleSpentInputs(txIds)
+                }
+                usedInputs.addAll(wtx.inputs)
+                services.recordTransactions(SignedTransaction(wtx.serialized, listOf(NullSignature), wtx.id))
             }
             return EnforceVerifyOrFail.Token
         } catch (exception: TransactionVerificationException) {