Merged in rnicoll-cash-issue-only (pull request #83)

Require that a cash Issue command is the only command

contracts/src/main/kotlin/contracts/Cash.kt

@@ -93,8 +93,10 @@ class Cash : Contract {
                 "there are no zero sized outputs" by outputs.none { it.amount.pennies == 0L }
             }
 
-            if (verifyIssueCommands(inputs, outputs, tx, currency, issuer)) continue
+            val issueCommand = tx.commands.select<Commands.Issue>().firstOrNull()
-
+            if (issueCommand != null) {
+                verifyIssueCommand(inputs, outputs, tx, issueCommand, currency, issuer)
+            } else {
                 val inputAmount = inputs.sumCashOrNull() ?: throw IllegalArgumentException("there is at least one cash input for this group")
                 val outputAmount = outputs.sumCashOrZero(currency)
 
@@ -112,13 +114,14 @@ class Cash : Contract {
                 verifyMoveCommands<Commands.Move>(inputs, tx)
             }
         }
-
-    private fun verifyIssueCommands(inputs: List<State>, outputs: List<State>, tx: TransactionForVerification, currency: Currency, issuer: Party): Boolean {
-        val issueCommand = tx.commands.select<Commands.Issue>().singleOrNull()
-        if (issueCommand == null || outputs.isEmpty()) {
-            return false
     }
 
+    private fun verifyIssueCommand(inputs: List<State>,
+                                   outputs: List<State>,
+                                   tx: TransactionForVerification,
+                                   issueCommand: AuthenticatedObject<Commands.Issue>,
+                                   currency: Currency,
+                                   issuer: Party) {
         // If we have an issue command, perform special processing: the group is allowed to have no inputs,
         // and the output states must have a deposit reference owned by the signer.
         //
@@ -132,12 +135,13 @@ class Cash : Contract {
         // The grouping ensures that all outputs have the same deposit reference and currency.
         val inputAmount = inputs.sumCashOrZero(currency)
         val outputAmount = outputs.sumCash()
+        val cashCommands = tx.commands.select<Cash.Commands>()
         requireThat {
             "the issue command has a nonce" by (issueCommand.value.nonce != 0L)
             "output deposits are owned by a command signer" by (issuer in issueCommand.signingParties)
             "output values sum to more than the inputs" by (outputAmount > inputAmount)
+            "there is only a single issue command" by (cashCommands.count() == 1)
         }
-        return true
     }
 
     /**

src/test/kotlin/contracts/CashTests.kt

@@ -143,6 +143,26 @@ class CashTests {
             arg(MEGA_CORP_PUBKEY) { Cash.Commands.Issue() }
             this `fails requirement` "output values sum to more than the inputs"
         }
+
+        // Can't have any other commands if we have an issue command (because the issue command overrules them)
+        transaction {
+            input { inState }
+            output { inState.copy(amount = inState.amount * 2) }
+            arg(MEGA_CORP_PUBKEY) { Cash.Commands.Issue() }
+            tweak {
+                arg(MEGA_CORP_PUBKEY) { Cash.Commands.Issue() }
+                this `fails requirement` "there is only a single issue command"
+            }
+            tweak {
+                arg(MEGA_CORP_PUBKEY) { Cash.Commands.Move() }
+                this `fails requirement` "there is only a single issue command"
+            }
+            tweak {
+                arg(MEGA_CORP_PUBKEY) { Cash.Commands.Exit(inState.amount / 2) }
+                this `fails requirement` "there is only a single issue command"
+            }
+            this.accepts()
+        }
     }
 
     @Test