fix(transaction): use arg.toObject() in fromObject for Transaction instances

fromObject called transaction.toObject() while the transaction variable was still undefined, so passing a Transaction instance threw "TypeError: Cannot read properties of undefined (reading 'toObject')". Read from the arg parameter, which holds the Transaction instance. Add a regression test for this previously uncovered path.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: Claude Code (claude-opus-4-8[1m]) <noreply@anthropic.com>

Author: 2 people

lib/transaction/transaction.js

@@ -472,7 +472,7 @@ Transaction.prototype.fromObject = function fromObject(arg) {
   var self = this;
   var transaction;
   if (arg instanceof Transaction) {
-    transaction = transaction.toObject();
+    transaction = arg.toObject();
   } else {
     transaction = arg;
   }

test/transaction/fromObject.js

@@ -0,0 +1,23 @@
+'use strict';
+
+require('chai').should();
+
+var bitcore = require('../../index-test');
+var Transaction = bitcore.Transaction;
+
+describe('Transaction', function() {
+
+  describe('#fromObject', function() {
+
+    it('builds from a Transaction instance and preserves its data', function() {
+      var source = new Transaction().lockUntilBlockHeight(123);
+
+      var target = new Transaction().fromObject(source);
+
+      target.nLockTime.should.equal(123);
+      target.toObject().should.deep.equal(source.toObject());
+    });
+
+  });
+
+});