qt: pay_lightning_invoice - attempt paying multiple times in case of failure

electrum/gui/qt/main_window.py

@@ -1664,13 +1664,37 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         self.do_send(preview = True)
 
     def pay_lightning_invoice(self, invoice):
-        try:
         amount = self.amount_e.get_amount()
-            f = self.wallet.lnworker.pay(invoice, amount_sat=amount)
-        except InvoiceError as e:
-            self.show_error(str(e))
-        else:
+        LN_NUM_PAYMENT_ATTEMPTS = 1  # TODO increase
+
+        def on_success(result):
+            self.print_error('ln payment success', result)
             self.do_clear()
+        def on_failure(exc_info):
+            type_, e, traceback = exc_info
+            if isinstance(e, PaymentFailure):
+                self.show_error(_('Payment failed. Tried {} times:\n{}')
+                                .format(LN_NUM_PAYMENT_ATTEMPTS, e))
+            elif isinstance(e, InvoiceError):
+                self.show_error(_('InvoiceError: {}').format(e))
+            else:
+                raise e
+        def task():
+            failure_list = []
+            for i in range(LN_NUM_PAYMENT_ATTEMPTS):
+                try:
+                    future = self.wallet.lnworker.pay(invoice, amount_sat=amount)
+                    future.result()
+                    break
+                except PaymentFailure as e:
+                    failure_list.append(e)
+                    # try again
+            else:
+                msg = '\n'.join(str(e) for e in failure_list)
+                raise PaymentFailure(msg)
+
+        msg = _('Sending lightning payment...')
+        WaitingDialog(self, msg, task, on_success, on_failure)
 
     def do_send(self, preview = False):
         if self.payto_e.is_lightning:

electrum/lnaddr.py

@@ -248,7 +248,9 @@ class LnAddr(object):
             ", ".join([k + '=' + str(v) for k, v in self.tags])
         )
 
-def lndecode(a, verbose=False, expected_hrp=constants.net.SEGWIT_HRP):
+def lndecode(a, verbose=False, expected_hrp=None):
+    if expected_hrp is None:
+        expected_hrp = constants.net.SEGWIT_HRP
     hrp, data = bech32_decode(a, ignore_long_length=True)
     if not hrp:
         raise ValueError("Bad bech32 checksum")

electrum/lnhtlc.py

@@ -511,10 +511,12 @@ class HTLCStateMachine(PrintError):
 
     @property
     def htlcs_in_local(self):
+        """in the local log. 'offered by us'"""
         return self.gen_htlc_indices("local")
 
     @property
     def htlcs_in_remote(self):
+        """in the remote log. 'offered by them'"""
         return self.gen_htlc_indices("remote")
 
     def settle_htlc(self, preimage, htlc_id):

electrum/lnworker.py

@@ -16,7 +16,8 @@ from .lnbase import Peer, privkey_to_pubkey, aiosafe
 from .lnaddr import lnencode, LnAddr, lndecode
 from .ecc import der_sig_from_sig_string
 from .lnhtlc import HTLCStateMachine
-from .lnutil import Outpoint, calc_short_channel_id, LNPeerAddr, get_compressed_pubkey_from_bech32
+from .lnutil import (Outpoint, calc_short_channel_id, LNPeerAddr, get_compressed_pubkey_from_bech32,
+                     PaymentFailure)
 from .lnwatcher import LNChanCloseHandler
 from .i18n import _
 
@@ -175,7 +176,6 @@ class LNWorker(PrintError):
         return asyncio.run_coroutine_threadsafe(coro, self.network.asyncio_loop)
 
     def pay(self, invoice, amount_sat=None):
-        # TODO try some number of paths (e.g. 10) in case of failures
         addr = lndecode(invoice, expected_hrp=constants.net.SEGWIT_HRP)
         payment_hash = addr.paymenthash
         invoice_pubkey = addr.pubkey.serialize()
@@ -185,7 +185,7 @@ class LNWorker(PrintError):
         amount_msat = int(amount_sat * 1000)
         path = self.network.path_finder.find_path_for_payment(self.pubkey, invoice_pubkey, amount_msat)
         if path is None:
-            raise Exception("No path found")
+            raise PaymentFailure(_("No path found"))
         node_id, short_channel_id = path[0]
         peer = self.peers[node_id]
         with self.lock:
@@ -194,7 +194,7 @@ class LNWorker(PrintError):
             if chan.short_channel_id == short_channel_id:
                 break
         else:
-            raise Exception("ChannelDB returned path with short_channel_id that is not in channel list")
+            raise Exception("ChannelDB returned path with short_channel_id {} that is not in channel list".format(bh2u(short_channel_id)))
         coro = peer.pay(path, chan, amount_msat, payment_hash, invoice_pubkey, addr.min_final_cltv_expiry)
         return asyncio.run_coroutine_threadsafe(coro, self.network.asyncio_loop)