allow paying invoice without amount. min feerate 253 sat/kw.

electrum/gui/qt/main_window.py

@@ -55,7 +55,7 @@ from electrum.util import (format_time, format_satoshis, format_fee_satoshis,
                            export_meta, import_meta, bh2u, bfh, InvalidPassword,
                            base_units, base_units_list, base_unit_name_to_decimal_point,
                            decimal_point_to_base_unit_name, quantize_feerate,
-                           UnknownBaseUnit, DECIMAL_POINT_DEFAULT)
+                           UnknownBaseUnit, DECIMAL_POINT_DEFAULT, InvoiceError)
 from electrum.transaction import Transaction, TxOutput
 from electrum.address_synchronizer import AddTransactionException
 from electrum.wallet import (Multisig_Wallet, CannotBumpFee, Abstract_Wallet,
@@ -1563,7 +1563,12 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         self.do_send(preview = True)
 
     def pay_lightning_invoice(self, invoice):
-        f = self.wallet.lnworker.pay(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:
             self.do_clear()
 
     def do_send(self, preview = False):
@@ -1788,6 +1793,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         self.payto_e.setFrozen(True)
         self.payto_e.setText(pubkey)
         self.message_e.setText(description)
+        if lnaddr.amount is not None:
             self.amount_e.setAmount(lnaddr.amount * COIN)
         #self.amount_e.textEdited.emit("")
         self.payto_e.is_lightning = True

electrum/lnbase.py

@@ -840,6 +840,7 @@ class Peer(PrintError):
         assert amount_msat > 0, "amount_msat is not greater zero"
         height = self.network.get_local_height()
         route = self.network.path_finder.create_route_from_path(path, self.lnworker.pubkey)
+        # TODO check that first edge (our channel) has enough balance to support amount_msat
         hops_data = []
         sum_of_deltas = sum(route_edge.channel_policy.cltv_expiry_delta for route_edge in route[1:])
         total_fee = 0
@@ -1028,7 +1029,7 @@ class Peer(PrintError):
         # TODO should use target_to_fee from master
         # target_to_fee(10*1000000) # 10 MB
         feerate_per_kvbyte = self.network.config.depth_to_fee(10)
-        feerate_per_kw = feerate_per_kvbyte / 4
+        feerate_per_kw = max(253, feerate_per_kvbyte // 4)
         self.print_error("current feerate", chan.remote_state.feerate)
         self.print_error("new feerate", feerate_per_kw)
         if feerate_per_kw < chan.remote_state.feerate / 2:

electrum/lnworker.py

@@ -9,7 +9,7 @@ import random
 
 from . import constants
 from .bitcoin import sha256, COIN
-from .util import bh2u, bfh, PrintError
+from .util import bh2u, bfh, PrintError, InvoiceError
 from .constants import set_testnet, set_simnet
 from .lnbase import Peer, privkey_to_pubkey, aiosafe
 from .lnaddr import lnencode, LnAddr, lndecode
@@ -18,6 +18,7 @@ from .transaction import Transaction
 from .lnhtlc import HTLCStateMachine
 from .lnutil import Outpoint, calc_short_channel_id
 from .lnwatcher import LNChanCloseHandler
+from .i18n import _
 
 # hardcoded nodes
 node_list = [
@@ -129,10 +130,10 @@ class LNWorker(PrintError):
                     peer = self.peers[chan.node_id]
                     peer.funding_locked(chan)
                 elif chan.state == "OPEN":
+                    peer = self.peers[chan.node_id]
                     if event == 'fee_histogram':
                         peer.on_bitcoin_fee_update(chan)
                     conf = self.wallet.get_tx_height(chan.funding_outpoint.txid)[1]
-                    peer = self.peers[chan.node_id]
                     peer.on_network_update(chan, conf)
         asyncio.run_coroutine_threadsafe(network_jobs(), self.network.asyncio_loop).result()
 
@@ -150,11 +151,14 @@ class LNWorker(PrintError):
         coro = self._open_channel_coroutine(node_id, local_amt_sat, push_amt_sat, None if pw == "" else pw)
         return asyncio.run_coroutine_threadsafe(coro, self.network.asyncio_loop)
 
-    def pay(self, invoice):
+    def pay(self, invoice, amount_sat=None):
         addr = lndecode(invoice, expected_hrp=constants.net.SEGWIT_HRP)
         payment_hash = addr.paymenthash
         invoice_pubkey = addr.pubkey.serialize()
-        amount_msat = int(addr.amount * COIN * 1000)
+        amount_sat = (addr.amount * COIN) if addr.amount else amount_sat
+        if amount_sat is None:
+            raise InvoiceError(_("Missing amount"))
+        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")

electrum/util.py

@@ -119,6 +119,9 @@ class WalletFileException(Exception): pass
 class BitcoinException(Exception): pass
 
 
+class InvoiceError(Exception): pass
+
+
 # Throw this exception to unwind the stack like when an error occurs.
 # However unlike other exceptions the user won't be informed.
 class UserCancelled(Exception):