Qt: allow to save invoices that have no amount

(such invoices are already saved by the QML GUI.)

electrum/gui/qt/invoice_list.py

@@ -179,7 +179,10 @@ class InvoiceList(MyTreeView):
             copy_menu.addAction(_("Address"), lambda: self.main_window.do_copy(invoice.get_address(), title='Bitcoin Address'))
         status = wallet.get_invoice_status(invoice)
         if status == PR_UNPAID:
-            menu.addAction(_("Pay") + "...", lambda: self.send_tab.do_pay_invoice(invoice))
+            if bool(invoice.get_amount_sat()):
+                menu.addAction(_("Pay") + "...", lambda: self.send_tab.do_pay_invoice(invoice))
+            else:
+                menu.addAction(_("Edit amount") + "...", lambda: self.send_tab.do_edit_invoice(invoice))
         if status == PR_FAILED:
             menu.addAction(_("Retry"), lambda: self.send_tab.do_pay_invoice(invoice))
         if self.wallet.lnworker:

electrum/gui/qt/paytoedit.py

@@ -364,9 +364,7 @@ class PayToEdit(Logger, GenericInputHandler):
             if is_max:
                 amount = '!'
             else:
-                amount = self.amount_edit.get_amount()
+                amount = self.amount_edit.get_amount() or 0
-                if amount is None:
-                    return []
             self.outputs = [PartialTxOutput(scriptpubkey=self.payto_scriptpubkey, value=amount)]
 
         return self.outputs[:]

electrum/gui/qt/send_tab.py

@@ -500,9 +500,6 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
                     amount_sat = self.amount_e.get_amount()
                     if amount_sat:
                         invoice.amount_msat = int(amount_sat * 1000)
-                    else:
-                        self.show_error(_('No amount'))
-                        return
                 if not self.wallet.has_lightning() and not invoice.can_be_paid_onchain():
                     self.show_error(_('Lightning is disabled'))
                     return
@@ -582,7 +579,16 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
             outputs += invoice.outputs
         self.pay_onchain_dialog(outputs)
 
+    def do_edit_invoice(self, invoice: 'Invoice'):
+        assert not bool(invoice.get_amount_sat())
+        text = invoice.lightning_invoice if invoice.is_lightning() else invoice.get_address()
+        self.payto_e._on_input_btn(text)
+        self.amount_e.setFocus()
+
     def do_pay_invoice(self, invoice: 'Invoice'):
+        if not bool(invoice.get_amount_sat()):
+            self.show_error(_('No amount'))
+            return
         if invoice.is_lightning():
             self.pay_lightning_invoice(invoice)
         else:

electrum/invoices.py

@@ -161,7 +161,8 @@ class BaseInvoice(StoredObject):
         Returns an integer satoshi amount, or '!' or None.
         Callers who need msat precision should call get_amount_msat()
         """
-        amount_msat = self.amount_msat
+        # return strictly positive value or None
+        amount_msat = self.amount_msat or None
         if amount_msat in [None, "!"]:
             return amount_msat
         return int(amount_msat // 1000)