txbatcher: allow duplicate outputs

Author: ecdsa

electrum/txbatcher.py

@@ -153,8 +153,14 @@ def to_pay_after(self, tx):
         # fixme: not robust to client restart, because we do not persist batch_payments
         if not tx:
             return self.batch_payments
-        # not robust to duplicates
-        return [x for x in self.batch_payments if x not in tx.outputs()]
+        to_pay = []
+        outputs = copy.deepcopy(tx.outputs())
+        for x in self.batch_payments:
+            if x not in outputs:
+                to_pay.append(x)
+            else:
+                outputs.remove(x)
+        return to_pay
 
     def to_sweep_after(self, tx):
         tx_prevouts = set(txin.prevout for txin in tx.inputs()) if tx else set()