wallet: make .fill() throw

lib/bcoin/wallet.js

@@ -247,7 +247,7 @@ Wallet.prototype.balance = function balance() {
   return this.tx.balance();
 };
 
-Wallet.prototype.fill = function fill(tx, cb) {
+Wallet.prototype.fill = function fill(tx) {
   // NOTE: tx should be prefilled with all outputs
   var cost = tx.funds('out');
 
@@ -257,12 +257,12 @@ Wallet.prototype.fill = function fill(tx, cb) {
   // total = cost + fee
   var total = cost.add(new bn(this.fee));
 
-  var lastAdded = -1;
+  var lastAdded = 0;
   function addInput(unspent, i) {
     // Add new inputs until TX will have enough funds to cover both
     // minimum post cost and fee
     tx.input(unspent);
-    lastAdded = i;
+    lastAdded++;
     return tx.funds('in').cmp(total) < 0;
   }
 
@@ -285,14 +285,14 @@ Wallet.prototype.fill = function fill(tx, cb) {
 
     // Failed to get enough funds, add more inputs
     if (tx.funds('in').cmp(total) < 0)
-      unspent.slice(lastAdded + 1).every(addInput, this);
+      unspent.slice(lastAdded).every(addInput, this);
   } while (tx.funds('in').cmp(total) < 0 && lastAdded < unspent.length);
 
   // Still failing to get enough funds, notify caller
   if (tx.funds('in').cmp(total) < 0) {
     var err = new Error('Not enough funds');
     err.minBalance = total;
-    return cb(err);
+    throw err;
   }
 
   // How much money is left after sending outputs

test/wallet-test.js

@@ -148,5 +148,11 @@ describe('Wallet', function() {
 
     assert.equal(t2.funds('in').toString(10), 16380);
     assert.equal(t2.funds('out').toString(10), 6380);
+
+    // Create new transaction
+    var t2 = bcoin.tx().out(w2, 15000);
+    assert.throws(function() {
+      w1.fill(t2);
+    });
   });
 });