Merge pull request #702 from Emurgo/evgenii/better_collateral_error

Add useful error for collateral return

rust/src/builders/tx_builder.rs

@@ -803,6 +803,13 @@ impl TransactionBuilder {
             ));
         }
         let col_input_value: Value = collateral.total_value()?;
+        let col_input_coin = col_input_value.coin;
+        if col_input_coin < *total_collateral {
+            return Err(JsError::from_str(
+                "Total collateral value cannot exceed the sum of collateral inputs",
+            ));
+        }
+
         let col_return: Value = col_input_value.checked_sub(&Value::new(&total_collateral))?;
         if col_return.multiasset.is_some() || col_return.coin > BigNum::zero() {
             let return_output = TransactionOutput::new(return_address, &col_return);

rust/src/tests/builders/tx_builder.rs

@@ -4923,6 +4923,35 @@ fn test_add_collateral_return_fails_no_enough_ada() {
     assert!(tx_builder.collateral_return.is_none());
 }
 
+#[test]
+fn test_add_collateral_return_fails_no_enough_ada_to_cover_return() {
+    let mut tx_builder = fake_reallistic_tx_builder();
+    tx_builder.set_fee(&BigNum(123456));
+
+    let masset = fake_multiasset(123);
+
+    let mut inp = TxInputsBuilder::new();
+    let collateral_input_value = 2_000_000;
+    inp.add_regular_input(
+        &fake_base_address(0),
+        &fake_tx_input(0),
+        &Value::new_with_assets(&BigNum(collateral_input_value.clone()), &masset),
+    ).expect("Failed to add input");
+
+    tx_builder.set_collateral(&inp);
+
+    let collateral_return_address = fake_base_address(1);
+
+    let total_collateral = BigNum(collateral_input_value + 1);
+
+    let coll_add_res = tx_builder
+        .set_total_collateral_and_return(&total_collateral, &collateral_return_address);
+
+    assert!(coll_add_res.is_err());
+    assert!(tx_builder.total_collateral.is_none());
+    assert!(tx_builder.collateral_return.is_none());
+}
+
 #[test]
 fn test_auto_calc_collateral_return_fails_on_no_collateral() {
     let mut tx_builder = fake_reallistic_tx_builder();