Validate balances are positive

marlowe/src/Language/Marlowe3/Semantics.hs

@@ -719,6 +719,13 @@ validatePayments pendingTx txOutPayments = let
     in all checkValidPayment listOfPayments
 
 
+{-|
+    Check that all accounts have positive balance.
+ -}
+validateBalances :: State -> Bool
+validateBalances State{..} = all (\(_, balance) -> balance > 0) (Map.toList accounts)
+
+
 {-|
     Marlowe Interpreter ValidatorScript generator.
 -}
@@ -740,6 +747,9 @@ mkValidator creator MarloweData{..} inputs pendingTx@PendingTx{..} = let
         Interval (LowerBound (Finite l) True) (UpperBound (Finite h) True) -> (l, h)
         _ -> traceErrorH "Tx valid slot must have lower bound and upper bounds"
 
+    positiveBalances = if validateBalances marloweState then True
+        else traceErrorH "Invalid contract state. There exists an account with non positive balance"
+
     validSignatures = let
         requiredSignatures = getSignatures inputs
         in checkSignatures pendingTx requiredSignatures
@@ -756,6 +766,7 @@ mkValidator creator MarloweData{..} inputs pendingTx@PendingTx{..} = let
     deposit = scriptInAmount - inputBalance
 
     preconditionsOk = checkCreator
+        && positiveBalances
         && validSignatures
         && balancesOk