qml: properly suggest paying bolt11 invoice onchain if insufficient LN balance.

Also, if fallback address is present, don't warn on bolt11 and no ln channels.

electrum/gui/qml/components/WalletMainView.qml

@@ -63,6 +63,29 @@ Item {
         dialog.open()
     }
 
+    function payOnchain() {
+        var dialog = confirmPaymentDialog.createObject(mainView, {
+                address: invoice.address,
+                satoshis: invoice.amountOverride.isEmpty
+                    ? invoice.amount
+                    : invoice.amountOverride,
+                message: invoice.message
+        })
+        var canComplete = !Daemon.currentWallet.isWatchOnly && Daemon.currentWallet.canSignWithoutCosigner
+        dialog.accepted.connect(function() {
+            if (!canComplete) {
+                if (Daemon.currentWallet.isWatchOnly) {
+                    dialog.finalizer.saveOrShow()
+                } else {
+                    dialog.finalizer.sign()
+                }
+            } else {
+                dialog.finalizer.signAndSend()
+            }
+        })
+        dialog.open()
+    }
+
     property QtObject menu: Menu {
         id: menu
 
@@ -327,29 +350,23 @@ Item {
             height: parent.height
 
             onDoPay: {
-                if (invoice.invoiceType == Invoice.OnchainInvoice
-                    || (invoice.invoiceType == Invoice.LightningInvoice
-                        && invoice.amountOverride.isEmpty
-                            ? invoice.amount.satsInt > Daemon.currentWallet.lightningCanSend
-                            : invoice.amountOverride.satsInt > Daemon.currentWallet.lightningCanSend
-                        ))
-                    {
-                    var dialog = confirmPaymentDialog.createObject(mainView, {
-                            address: invoice.address,
-                            satoshis: invoice.amountOverride.isEmpty ? invoice.amount : invoice.amountOverride,
-                            message: invoice.message
+                var lninvoiceButPayOnchain = false
+                if (invoice.invoiceType == Invoice.LightningInvoice && invoice.address) {
+                    // ln invoice with fallback
+                    var amountToSend = invoice.amountOverride.isEmpty
+                        ? invoice.amount.satsInt
+                        : invoice.amountOverride.satsInt
+                    if (amountToSend > Daemon.currentWallet.lightningCanSend.satsInt) {
+                        lninvoiceButPayOnchain = true
+                    }
+                }
+                if (invoice.invoiceType == Invoice.OnchainInvoice || lninvoiceButPayOnchain) {
+                    var dialog = app.messageDialog.createObject(mainView, {
+                        title: qsTr('Insufficient balance to pay over Lightning. Pay on-chain instead?'),
+                        yesno: true
                     })
-                    var canComplete = !Daemon.currentWallet.isWatchOnly && Daemon.currentWallet.canSignWithoutCosigner
                     dialog.accepted.connect(function() {
-                        if (!canComplete) {
-                            if (Daemon.currentWallet.isWatchOnly) {
-                                dialog.finalizer.saveOrShow()
-                            } else {
-                                dialog.finalizer.sign()
-                            }
-                        } else {
-                            dialog.finalizer.signAndSend()
-                        }
+                        payOnchain()
                     })
                     dialog.open()
                 } else if (invoice.invoiceType == Invoice.LightningInvoice) {

electrum/gui/qml/qeinvoice.py

@@ -1,6 +1,4 @@
-import threading
-from typing import TYPE_CHECKING, Optional, Dict, Any
-import asyncio
+from typing import Optional, Dict, Any
 from urllib.parse import urlparse
 
 from PyQt5.QtCore import pyqtProperty, pyqtSignal, pyqtSlot, QObject, Q_ENUMS, QTimer
@@ -9,16 +7,11 @@ from electrum.i18n import _
 from electrum.logging import get_logger
 from electrum.invoices import (Invoice, PR_UNPAID, PR_EXPIRED, PR_UNKNOWN, PR_PAID, PR_INFLIGHT,
                                PR_FAILED, PR_ROUTING, PR_UNCONFIRMED, PR_BROADCASTING, PR_BROADCAST, LN_EXPIRY_NEVER)
-from electrum.lnaddr import LnInvoiceException
 from electrum.transaction import PartialTxOutput, TxOutput
-from electrum.util import InvoiceError, get_asyncio_loop
-from electrum.lnutil import format_short_channel_id, IncompatibleOrInsaneFeatures
-from electrum.lnurl import decode_lnurl, request_lnurl, callback_lnurl
+from electrum.lnutil import format_short_channel_id
 from electrum.bitcoin import COIN
 from electrum.paymentrequest import PaymentRequest
-from electrum.payment_identifier import (maybe_extract_lightning_payment_identifier,
-                                         PaymentIdentifier, PaymentIdentifierState, PaymentIdentifierType)
-from electrum.bip21 import parse_bip21_URI, InvalidBitcoinURI
+from electrum.payment_identifier import (PaymentIdentifier, PaymentIdentifierState, PaymentIdentifierType)
 from .qetypes import QEAmount
 from .qewallet import QEWallet
 from .util import status_update_timer_interval, QtEventListener, event_listener
@@ -392,6 +385,7 @@ class QEInvoice(QObject, QtEventListener):
     def get_max_spendable_lightning(self):
         return self._wallet.wallet.lnworker.num_sats_can_send() if self._wallet.wallet.lnworker else 0
 
+
 class QEInvoiceParser(QEInvoice):
     _logger = get_logger(__name__)
 
@@ -530,10 +524,9 @@ class QEInvoiceParser(QEInvoice):
                     self.validationError.emit('no_lightning',
                         _('Detected valid Lightning invoice, but Lightning not enabled for wallet and no fallback address found.'))
                     return
-                if self._wallet.wallet.lnworker and not self._wallet.wallet.lnworker.channels:
+                if self._wallet.wallet.lnworker and not self._wallet.wallet.lnworker.channels and not lninvoice.get_address():
                     self.validationWarning.emit('no_channels',
                         _('Detected valid Lightning invoice, but there are no open channels'))
-
                 self.setValidLightningInvoice(lninvoice)
                 self.validationSuccess.emit()
             elif self._pi.type == PaymentIdentifierType.BIP21:
@@ -544,7 +537,6 @@ class QEInvoiceParser(QEInvoice):
                 else:
                     self._validateRecipient_bip21_onchain(self._pi.bip21)
 
-
     def _validateRecipient_bip21_onchain(self, bip21: Dict[str, Any]) -> None:
         if 'amount' not in bip21:
             amount = 0