lightning: assert result type, add invoice qr dialog

gui/qt/lightning_invoice_list.py

@@ -5,6 +5,7 @@ from PyQt5 import QtCore, QtWidgets
 from collections import OrderedDict
 import logging
 from electrum.lightning import lightningCall
+from .qrcodewidget import QRDialog
 
 mapping = {0: "r_hash", 1: "pay_req", 2: "settled"}
 revMapp = {"r_hash": 0, "pay_req": 1, "settled": 2}
@@ -61,7 +62,11 @@ class LightningInvoiceList(QtWidgets.QWidget):
         def copy():
             print(pay_req)
             cb.setText(pay_req)
+        def qr():
+            d = QRDialog(pay_req, self, "Lightning invoice")
+            d.exec_()
         menu.addAction("Copy payment request", copy)
+        menu.addAction("Show payment request as QR code", qr)
         menu.exec_(self._tv.viewport().mapToGlobal(position))
     def lightningWorkerHandler(self, sourceClassName, obj):
         new = {}

lib/lightning.py

@@ -625,6 +625,7 @@ class LightningRPC:
                     raise
                 toprint = result
                 try:
+                    assert type(result) is not str, result
                     assert result["stderr"] == "" and result["returncode"] == 0, "LightningRPC detected error: " + result["stderr"]
                     toprint = json.loads(result["stdout"])
                     for i in self.subscribers: applyMethodName(i)(toprint)