add check for 0 unspents in createTransaction

Summary: It is clearer if we throw an Error here early on in the createTransaction function because then we won't try to build a transaction using 0 unspents (which results in a transaction with 0 inputs!)

Reviewers: ben

Reviewed By: ben

Subscribers: ben

Differential Revision: https://phabricator.bitgo.com/D6193

Author: Alex Melville

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bitgo",
-  "version": "3.5.1",
+  "version": "3.5.2",
   "description": "BitGo Javascript SDK",
   "main": "./src/index.js",
   "keywords": [

src/transactionBuilder.js

@@ -286,6 +286,11 @@ exports.createTransaction = function(params) {
           return confirms >= minConfirms;
         });
 
+        // abort early if there's no viable unspents, because it won't be possible to create the txn later
+        if (unspents.length === 0) {
+          throw Error('0 unspents available for transaction creation');
+        }
+
         // create array of unconfirmed unspent ID strings of the form "txHash:outputIndex"
         zeroConfUnspentTxIds = _(results.unspents).filter(function(u) {
           return !u.confirmations;

test/wallet.js

@@ -2261,11 +2261,22 @@ describe('Wallet API', function() {
         err.message.should.include("invalid bitcoin address");
         return wallet1.sendMany({ recipients: [{ address: TestBitGo.TEST_WALLET2_ADDRESS, amount: -100 }], walletPassphrase: TestBitGo.TEST_WALLET1_PASSCODE });
       })
-      .then(function(result) {
+      .then(function() {
         throw new Error("Unexpected result - expected to catch bad amount");
       })
       .catch(function(err) {
         err.message.should.include("invalid amount");
+        // use a ridiculously high number for the minConfirms so that no viable unspents are returned
+        return bitgo.unlock({ otp: '0000000' });
+      })
+      .then(function() {
+        return wallet1.sendMany({ recipients: [{ address: TestBitGo.TEST_WALLET2_ADDRESS, amount: 10000 }], walletPassphrase: TestBitGo.TEST_WALLET1_PASSCODE, enforceMinConfirmsForChange: true, minConfirms: 999999999 });
+      })
+      .then(function() {
+        throw new Error("Unexpected result - expected to catch 0 unspents");
+      })
+      .catch(function(err) {
+        err.message.should.include('0 unspents available for transaction creation');
       });
     });