fix(psbt): do not use BIP174 tobuffer method in clone

We want to use the toBuffer methods that we implement in child classes of
PSBT, not just the bip174 serialization. For the PSBT class, this will
automatically default to bip174 serialization.

Author: davidkaplanbitgo

src/psbt.js

@@ -152,7 +152,7 @@ class Psbt {
   }
   clone() {
     // TODO: more efficient cloning
-    const res = this.constructor.fromBuffer(this.data.toBuffer(), this.opts);
+    const res = this.constructor.fromBuffer(this.toBuffer(), this.opts);
     res.opts = JSON.parse(JSON.stringify(this.opts));
     return res;
   }

test/psbt.spec.ts

@@ -896,6 +896,20 @@ describe(`Psbt`, () => {
       assert.notStrictEqual(clone.toBase64(), notAClone.toBase64());
       assert.strictEqual(psbt.toBase64(), notAClone.toBase64());
     });
+
+    it('Should use the proper toBuffer method when cloning', () => {
+      class PsbtSubclass extends Psbt {
+        toBuffer(): Buffer {
+          super.setLocktime(1000);
+          return super.toBuffer();
+        }
+      }
+      const psbt = new PsbtSubclass();
+      assert.strictEqual(psbt.extractTransaction().locktime, 0);
+
+      const clone = psbt.clone();
+      assert.strictEqual(clone.extractTransaction().locktime, 1000);
+    });
   });
 
   describe('setMaximumFeeRate', () => {

ts_src/psbt.ts

@@ -217,7 +217,7 @@ export class Psbt {
   clone(): Psbt {
     // TODO: more efficient cloning
     const res = (this.constructor as typeof Psbt).fromBuffer(
-      this.data.toBuffer(),
+      this.toBuffer(),
       this.opts,
     );
     res.opts = JSON.parse(JSON.stringify(this.opts));