Pass make_tx function to ConfirmTxDialog

- allow 'spend max' when opening a channel (fixes #5698)
 - display amount minus fee when 'max' buttons are pressed
 - estimate fee of channel funding using a template with dummy address

electrum/commands.py

@@ -52,6 +52,7 @@ from .wallet import Abstract_Wallet, create_new_wallet, restore_wallet_from_text
 from .address_synchronizer import TX_HEIGHT_LOCAL
 from .mnemonic import Mnemonic
 from .lnutil import SENT, RECEIVED
+from .lnutil import ln_dummy_address
 from .lnpeer import channel_id_from_funding_tx
 from .plugin import run_hook
 from .version import ELECTRUM_VERSION
@@ -922,8 +923,12 @@ class Commands:
         return True
 
     @command('wpn')
-    async def open_channel(self, connection_string, amount, channel_push=0, password=None, wallet: Abstract_Wallet = None):
-        chan = await wallet.lnworker._open_channel_coroutine(connection_string, satoshis(amount), satoshis(channel_push), password)
+    async def open_channel(self, connection_string, amount, push_amount=0, password=None, wallet: Abstract_Wallet = None):
+        funding_sat = satoshis(amount)
+        push_sat = satoshis(push_amount)
+        dummy_output = PartialTxOutput.from_address_and_value(ln_dummy_address(), funding_sat)
+        funding_tx = wallet.mktx(outputs = [dummy_output], rbf=False, sign=False, nonlocal_only=True)
+        chan = await wallet.lnworker._open_channel_coroutine(connection_string, funding_tx, funding_sat, push_sat, password)
         return chan.funding_outpoint.to_str()
 
     @command('wn')
@@ -1037,7 +1042,7 @@ command_options = {
     'timeout':     (None, "Timeout in seconds"),
     'force':       (None, "Create new address beyond gap limit, if no more addresses are available."),
     'pending':     (None, "Show only pending requests."),
-    'channel_push':(None, 'Push initial amount (in BTC)'),
+    'push_amount': (None, 'Push initial amount (in BTC)'),
     'expired':     (None, "Show only expired requests."),
     'paid':        (None, "Show only paid requests."),
     'show_addresses': (None, "Show input and output addresses"),

electrum/gui/qt/channels_list.py

@@ -5,15 +5,15 @@ from enum import IntEnum
 
 from PyQt5 import QtCore, QtWidgets, QtGui
 from PyQt5.QtCore import Qt
-from PyQt5.QtWidgets import QMenu, QHBoxLayout, QLabel, QVBoxLayout, QGridLayout, QLineEdit
+from PyQt5.QtWidgets import QMenu, QHBoxLayout, QLabel, QVBoxLayout, QGridLayout, QLineEdit, QPushButton
 
 from electrum.util import inv_dict, bh2u, bfh
 from electrum.i18n import _
 from electrum.lnchannel import Channel
 from electrum.wallet import Abstract_Wallet
-from electrum.lnutil import LOCAL, REMOTE, ConnStringFormatError, format_short_channel_id
+from electrum.lnutil import LOCAL, REMOTE, ConnStringFormatError, format_short_channel_id, LN_MAX_FUNDING_SAT
 
-from .util import MyTreeView, WindowModalDialog, Buttons, OkButton, CancelButton, EnterButton, WWLabel, WaitingDialog
+from .util import MyTreeView, WindowModalDialog, Buttons, OkButton, CancelButton, EnterButton, WWLabel, WaitingDialog, HelpLabel
 from .amountedit import BTCAmountEdit
 from .channel_details import ChannelDetailsDialog
 
@@ -162,26 +162,38 @@ class ChannelsList(MyTreeView):
     def new_channel_dialog(self):
         lnworker = self.parent.wallet.lnworker
         d = WindowModalDialog(self.parent, _('Open Channel'))
-        d.setMinimumWidth(700)
         vbox = QVBoxLayout(d)
-        h = QGridLayout()
+        vbox.addWidget(QLabel(_('Enter Remote Node ID or connection string or invoice')))
         local_nodeid = QLineEdit()
+        local_nodeid.setMinimumWidth(700)
         local_nodeid.setText(bh2u(lnworker.node_keypair.pubkey))
         local_nodeid.setReadOnly(True)
         local_nodeid.setCursorPosition(0)
         remote_nodeid = QLineEdit()
-        local_amt_inp = BTCAmountEdit(self.parent.get_decimal_point)
-        local_amt_inp.setAmount(200000)
-        push_amt_inp = BTCAmountEdit(self.parent.get_decimal_point)
-        push_amt_inp.setAmount(0)
+        remote_nodeid.setMinimumWidth(700)
+        amount_e = BTCAmountEdit(self.parent.get_decimal_point)
+        # max button
+        def spend_max():
+            make_tx = self.parent.mktx_for_open_channel('!')
+            tx = make_tx(None)
+            amount = tx.output_value()
+            amount = min(amount, LN_MAX_FUNDING_SAT)
+            amount_e.setAmount(amount)
+            amount_e.setFrozen(True)
+        max_button = EnterButton(_("Max"), spend_max)
+        max_button.setFixedWidth(100)
+        max_button.setCheckable(True)
+        h = QGridLayout()
         h.addWidget(QLabel(_('Your Node ID')), 0, 0)
         h.addWidget(local_nodeid, 0, 1)
-        h.addWidget(QLabel(_('Remote Node ID or connection string or invoice')), 1, 0)
+        h.addWidget(QLabel(_('Remote Node ID')), 1, 0)
         h.addWidget(remote_nodeid, 1, 1)
-        h.addWidget(QLabel('Local amount'), 2, 0)
-        h.addWidget(local_amt_inp, 2, 1)
-        h.addWidget(QLabel('Push amount'), 3, 0)
-        h.addWidget(push_amt_inp, 3, 1)
+        h.addWidget(QLabel('Amount'), 2, 0)
+        hbox = QHBoxLayout()
+        hbox.addWidget(amount_e)
+        hbox.addWidget(max_button)
+        hbox.addStretch(1)
+        h.addLayout(hbox, 2, 1)
         vbox.addLayout(h)
         ok_button = OkButton(d)
         ok_button.setDefault(True)
@@ -191,7 +203,6 @@ class ChannelsList(MyTreeView):
         remote_nodeid.setCursorPosition(0)
         if not d.exec_():
             return
-        local_amt = local_amt_inp.get_amount()
-        push_amt = push_amt_inp.get_amount()
-        connect_contents = str(remote_nodeid.text()).strip()
-        self.parent.open_channel(connect_contents, local_amt, push_amt)
+        funding_sat = '!' if max_button.isChecked() else amount_e.get_amount()
+        connect_str = str(remote_nodeid.text()).strip()
+        self.parent.open_channel(connect_str, funding_sat, 0)

electrum/gui/qt/confirm_tx_dialog.py

@@ -51,18 +51,17 @@ if TYPE_CHECKING:
 
 class TxEditor:
 
-    def __init__(self, window: 'ElectrumWindow', inputs, outputs, external_keypairs):
+    def __init__(self, window: 'ElectrumWindow', make_tx, output_value, is_sweep):
         self.main_window = window
-        self.outputs = outputs
-        self.get_coins = inputs
+        self.make_tx = make_tx
+        self.output_value = output_value
         self.tx = None  # type: Optional[Transaction]
         self.config = window.config
         self.wallet = window.wallet
-        self.external_keypairs = external_keypairs
         self.not_enough_funds = False
         self.no_dynfee_estimates = False
         self.needs_update = False
-        self.password_required = self.wallet.has_keystore_encryption() and not external_keypairs
+        self.password_required = self.wallet.has_keystore_encryption() and not is_sweep
         self.main_window.gui_object.timer.timeout.connect(self.timer_actions)
 
     def timer_actions(self):
@@ -86,17 +85,8 @@ class TxEditor:
 
     def update_tx(self):
         fee_estimator = self.get_fee_estimator()
-        is_sweep = bool(self.external_keypairs)
-        coins = self.get_coins()
-        # deepcopy outputs because '!' is converted to number
-        outputs = copy.deepcopy(self.outputs)
-        make_tx = lambda fee_est: self.wallet.make_unsigned_transaction(
-            coins=coins,
-            outputs=outputs,
-            fee=fee_est,
-            is_sweep=is_sweep)
         try:
-            self.tx = make_tx(fee_estimator)
+            self.tx = self.make_tx(fee_estimator)
             self.not_enough_funds = False
             self.no_dynfee_estimates = False
         except NotEnoughFunds:
@@ -107,7 +97,7 @@ class TxEditor:
             self.no_dynfee_estimates = True
             self.tx = None
             try:
-                self.tx = make_tx(0)
+                self.tx = self.make_tx(0)
             except BaseException:
                 return
         except InternalAddressCorruption as e:
@@ -131,9 +121,9 @@ class TxEditor:
 class ConfirmTxDialog(TxEditor, WindowModalDialog):
     # set fee and return password (after pw check)
 
-    def __init__(self, window: 'ElectrumWindow', inputs, outputs, external_keypairs):
+    def __init__(self, window: 'ElectrumWindow', make_tx, output_value, is_sweep):
 
-        TxEditor.__init__(self, window, inputs, outputs, external_keypairs)
+        TxEditor.__init__(self, window, make_tx, output_value, is_sweep)
         WindowModalDialog.__init__(self, window, _("Confirm Transaction"))
         vbox = QVBoxLayout()
         self.setLayout(vbox)
@@ -218,9 +208,7 @@ class ConfirmTxDialog(TxEditor, WindowModalDialog):
 
     def update(self):
         tx = self.tx
-        output_values = [x.value for x in self.outputs]
-        is_max = '!' in output_values
-        amount = tx.output_value() if is_max else sum(output_values)
+        amount = tx.output_value() if self.output_value == '!' else self.output_value
         self.amount_label.setText(self.main_window.format_amount_and_units(amount))
 
         if self.not_enough_funds:

electrum/gui/qt/main_window.py

@@ -76,6 +76,7 @@ from electrum.simple_config import SimpleConfig
 from electrum.logging import Logger
 from electrum.util import PR_PAID, PR_UNPAID, PR_INFLIGHT, PR_FAILED
 from electrum.util import pr_expiration_values
+from electrum.lnutil import ln_dummy_address
 
 from .exception_window import Exception_Hook
 from .amountedit import AmountEdit, BTCAmountEdit, MyLineEdit, FeerateEdit
@@ -1282,8 +1283,18 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
     def spend_max(self):
         if run_hook('abort_send', self):
             return
+        outputs = self.payto_e.get_outputs(True)
+        if not outputs:
+            return
         self.max_button.setChecked(True)
-        amount = sum(x.value_sats() for x in self.get_coins())
+        make_tx = lambda fee_est: self.wallet.make_unsigned_transaction(
+            coins=self.get_coins(),
+            outputs=outputs,
+            fee=fee_est,
+            is_sweep=False)
+
+        tx = make_tx(None)
+        amount = tx.output_value()#sum(x.value_sats() for x in self.get_coins())
         self.amount_e.setAmount(amount)
         ## substract extra fee
         #__, x_fee_amount = run_hook('get_tx_extra_fee', self.wallet, tx) or (None, 0)
@@ -1448,20 +1459,20 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         outputs = []
         for invoice in invoices:
             outputs += invoice['outputs']
-        self.pay_onchain_dialog(self.get_coins, outputs)
+        self.pay_onchain_dialog(self.get_coins(), outputs)
 
     def do_pay_invoice(self, invoice):
         if invoice['type'] == PR_TYPE_LN:
             self.pay_lightning_invoice(invoice['invoice'])
         elif invoice['type'] == PR_TYPE_ONCHAIN:
             outputs = invoice['outputs']
-            self.pay_onchain_dialog(self.get_coins, outputs, invoice=invoice)
+            self.pay_onchain_dialog(self.get_coins(), outputs, invoice=invoice)
         else:
             raise Exception('unknown invoice type')
 
-    def get_coins(self):
+    def get_coins(self, nonlocal_only=False):
         coins = self.get_manually_selected_coins()
-        return coins or self.wallet.get_spendable_coins(None)
+        return coins or self.wallet.get_spendable_coins(None, nonlocal_only=nonlocal_only)
 
     def get_manually_selected_coins(self) -> Sequence[PartialTxInput]:
         return self.utxo_list.get_spend_list()
@@ -1470,10 +1481,19 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         # trustedcoin requires this
         if run_hook('abort_send', self):
             return
+        is_sweep = bool(external_keypairs)
+        make_tx = lambda fee_est: self.wallet.make_unsigned_transaction(
+            coins=inputs,
+            outputs=outputs,
+            fee=fee_est,
+            is_sweep=is_sweep)
         if self.config.get('advanced_preview'):
-            self.preview_tx_dialog(inputs, outputs, invoice=invoice)
+            self.preview_tx_dialog(make_tx, outputs, is_sweep=is_sweep, invoice=invoice)
             return
-        d = ConfirmTxDialog(self, inputs, outputs, external_keypairs)
+
+        output_values = [x.value for x in outputs]
+        output_value = '!' if '!' in output_values else sum(output_values)
+        d = ConfirmTxDialog(self, make_tx, output_value, is_sweep)
         d.update_tx()
         if d.not_enough_funds:
             self.show_message(_('Not Enough Funds'))
@@ -1487,10 +1507,10 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
                     self.broadcast_or_show(tx, invoice=invoice)
             self.sign_tx_with_password(tx, sign_done, password, external_keypairs)
         else:
-            self.preview_tx_dialog(inputs, outputs, external_keypairs=external_keypairs, invoice=invoice)
+            self.preview_tx_dialog(make_tx, outputs, is_sweep=is_sweep, invoice=invoice)
 
-    def preview_tx_dialog(self, inputs, outputs, external_keypairs=None, invoice=None):
-        d = PreviewTxDialog(inputs, outputs, external_keypairs, window=self, invoice=invoice)
+    def preview_tx_dialog(self, make_tx, outputs, is_sweep=False, invoice=None):
+        d = PreviewTxDialog(make_tx, outputs, is_sweep, window=self, invoice=invoice)
         d.show()
 
     def broadcast_or_show(self, tx, invoice=None):
@@ -1572,21 +1592,26 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         WaitingDialog(self, _('Broadcasting transaction...'),
                       broadcast_thread, broadcast_done, self.on_error)
 
-    def open_channel(self, connect_str, local_amt, push_amt):
+    def mktx_for_open_channel(self, funding_sat):
+        coins = self.get_coins(nonlocal_only=True)
+        make_tx = partial(self.wallet.lnworker.mktx_for_open_channel, coins, funding_sat)
+        return make_tx
+
+    def open_channel(self, connect_str, funding_sat, push_amt):
         # use ConfirmTxDialog
         # we need to know the fee before we broadcast, because the txid is required
         # however, the user must not be allowed to broadcast early
-        funding_sat = local_amt + push_amt
-        inputs = self.get_coins
-        outputs = [PartialTxOutput.from_address_and_value(self.wallet.dummy_address(), funding_sat)]
-        d = ConfirmTxDialog(self, inputs, outputs, None)
-        cancelled, is_send, password, tx = d.run()
+        make_tx = self.mktx_for_open_channel(funding_sat)
+        d = ConfirmTxDialog(self, make_tx, funding_sat, False)
+        cancelled, is_send, password, funding_tx = d.run()
         if not is_send:
             return
         if cancelled:
             return
+        # read funding_sat from tx; converts '!' to int value
+        funding_sat = funding_tx.output_value_for_address(ln_dummy_address())
         def task():
-            return self.wallet.lnworker.open_channel(connect_str, local_amt, push_amt, password)
+            return self.wallet.lnworker.open_channel(connect_str, funding_tx, funding_sat, push_amt, password)
         def on_success(chan):
             n = chan.constraints.funding_txn_minimum_depth
             message = '\n'.join([
@@ -2647,7 +2672,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         scriptpubkey = bfh(bitcoin.address_to_script(addr))
         outputs = [PartialTxOutput(scriptpubkey=scriptpubkey, value='!')]
         self.warn_if_watching_only()
-        self.pay_onchain_dialog(lambda: coins, outputs, invoice=None, external_keypairs=keypairs)
+        self.pay_onchain_dialog(coins, outputs, invoice=None, external_keypairs=keypairs)
 
     def _do_import(self, title, header_layout, func):
         text = text_dialog(self, title, header_layout, _('Import'), allow_multi=True)

electrum/gui/qt/transaction_dialog.py

@@ -602,8 +602,8 @@ class TxDialog(BaseTxDialog):
 
 class PreviewTxDialog(BaseTxDialog, TxEditor):
 
-    def __init__(self, inputs, outputs, external_keypairs, *, window: 'ElectrumWindow', invoice):
-        TxEditor.__init__(self, window, inputs, outputs, external_keypairs)
+    def __init__(self, make_tx, outputs, is_sweep, *, window: 'ElectrumWindow', invoice):
+        TxEditor.__init__(self, window, make_tx, outputs, is_sweep)
         BaseTxDialog.__init__(self, parent=window, invoice=invoice, desc='', prompt_if_unsaved=False, finalized=False)
         self.update_tx()
         self.update()

electrum/lnpeer.py

@@ -46,10 +46,12 @@ from .lntransport import LNTransport, LNTransportBase
 from .lnmsg import encode_msg, decode_msg
 from .interface import GracefulDisconnect, NetworkException
 from .lnrouter import fee_for_edge_msat
+from .lnutil import ln_dummy_address
 
 if TYPE_CHECKING:
     from .lnworker import LNWorker, LNGossip, LNWallet
     from .lnrouter import RouteEdge
+    from .transaction import PartialTransaction
 
 
 LN_P2P_NETWORK_TIMEOUT = 20
@@ -479,12 +481,8 @@ class Peer(Logger):
         return local_config
 
     @log_exceptions
-    async def channel_establishment_flow(self, password: Optional[str], funding_sat: int,
+    async def channel_establishment_flow(self, password: Optional[str], funding_tx: 'PartialTransaction', funding_sat: int, 
                                          push_msat: int, temp_channel_id: bytes) -> Channel:
-        wallet = self.lnworker.wallet
-        # dry run creating funding tx to see if we even have enough funds
-        funding_tx_test = wallet.mktx(outputs=[PartialTxOutput.from_address_and_value(wallet.dummy_address(), funding_sat)],
-                                      password=password, nonlocal_only=True)
         await asyncio.wait_for(self.initialized.wait(), LN_P2P_NETWORK_TIMEOUT)
         feerate = self.lnworker.current_feerate_per_kw()
         local_config = self.make_local_config(funding_sat, push_msat, LOCAL)
@@ -555,16 +553,19 @@ class Peer(Logger):
             initial_msat=push_msat,
             reserve_sat = remote_reserve_sat,
             htlc_minimum_msat = htlc_min,
-
             next_per_commitment_point=remote_per_commitment_point,
             current_per_commitment_point=None,
             revocation_store=their_revocation_store,
         )
-        # create funding tx
+        # replace dummy output in funding tx
         redeem_script = funding_output_script(local_config, remote_config)
         funding_address = bitcoin.redeem_script_to_address('p2wsh', redeem_script)
         funding_output = PartialTxOutput.from_address_and_value(funding_address, funding_sat)
-        funding_tx = wallet.mktx(outputs=[funding_output], password=password, nonlocal_only=True)
+        dummy_output = PartialTxOutput.from_address_and_value(ln_dummy_address(), funding_sat)
+        funding_tx.outputs().remove(dummy_output)
+        funding_tx.add_outputs([funding_output])
+        funding_tx.set_rbf(False)
+        self.lnworker.wallet.sign_transaction(funding_tx, password)
         funding_txid = funding_tx.txid()
         funding_index = funding_tx.outputs().index(funding_output)
         # remote commitment transaction

electrum/lnutil.py

@@ -27,6 +27,11 @@ if TYPE_CHECKING:
 HTLC_TIMEOUT_WEIGHT = 663
 HTLC_SUCCESS_WEIGHT = 703
 
+LN_MAX_FUNDING_SAT = pow(2, 24)
+
+# dummy address for fee estimation of funding tx
+def ln_dummy_address():
+    return redeem_script_to_address('p2wsh', '')
 
 class Keypair(NamedTuple):
     pubkey: bytes

electrum/lnworker.py

@@ -24,6 +24,7 @@ from . import keystore
 from .util import profiler
 from .util import PR_UNPAID, PR_EXPIRED, PR_PAID, PR_INFLIGHT, PR_FAILED
 from .util import PR_TYPE_LN
+from .lnutil import LN_MAX_FUNDING_SAT
 from .keystore import BIP32_KeyStore
 from .bitcoin import COIN
 from .transaction import Transaction
@@ -48,6 +49,8 @@ from .lnutil import (Outpoint, LNPeerAddr,
                      NUM_MAX_EDGES_IN_PAYMENT_PATH, SENT, RECEIVED, HTLCOwner,
                      UpdateAddHtlc, Direction, LnLocalFeatures, format_short_channel_id,
                      ShortChannelID)
+from .lnutil import ln_dummy_address
+from .transaction import PartialTxOutput
 from .lnonion import OnionFailureCode
 from .lnmsg import decode_msg
 from .i18n import _
@@ -768,13 +771,14 @@ class LNWallet(LNWorker):
                     await self.force_close_channel(chan.channel_id)
 
     @log_exceptions
-    async def _open_channel_coroutine(self, connect_str, local_amount_sat, push_sat, password):
+    async def _open_channel_coroutine(self, connect_str, funding_tx, funding_sat, push_sat, password):
         peer = await self.add_peer(connect_str)
         # peer might just have been connected to
         await asyncio.wait_for(peer.initialized.wait(), LN_P2P_NETWORK_TIMEOUT)
         chan = await peer.channel_establishment_flow(
             password,
-            funding_sat=local_amount_sat + push_sat,
+            funding_tx=funding_tx,
+            funding_sat=funding_sat,
             push_msat=push_sat * 1000,
             temp_channel_id=os.urandom(32))
         self.save_channel(chan)
@@ -805,8 +809,19 @@ class LNWallet(LNWorker):
             peer = await self._add_peer(host, port, node_id)
         return peer
 
-    def open_channel(self, connect_str, local_amt_sat, push_amt_sat, password=None, timeout=20):
-        coro = self._open_channel_coroutine(connect_str, local_amt_sat, push_amt_sat, password)
+    def mktx_for_open_channel(self, coins, funding_sat, fee_est):
+        dummy_address = ln_dummy_address()
+        outputs = [PartialTxOutput.from_address_and_value(dummy_address, funding_sat)]
+        tx = self.wallet.make_unsigned_transaction(
+            coins=coins,
+            outputs=outputs,
+            fee=fee_est)
+        tx.set_rbf(False)
+        return tx
+
+    def open_channel(self, connect_str, funding_tx, funding_sat, push_amt_sat, password=None, timeout=20):
+        assert funding_sat <= LN_MAX_FUNDING_SAT
+        coro = self._open_channel_coroutine(connect_str, funding_tx, funding_sat, push_amt_sat, password)
         fut = asyncio.run_coroutine_threadsafe(coro, self.network.asyncio_loop)
         try:
             chan = fut.result(timeout=timeout)

electrum/tests/regtest/regtest.sh

@@ -109,8 +109,8 @@ fi
 
 if [[ $1 == "open" ]]; then
     bob_node=$($bob nodeid)
-    channel_id1=$($alice open_channel $bob_node 0.001 --channel_push 0.001)
-    channel_id2=$($carol open_channel $bob_node 0.001 --channel_push 0.001)
+    channel_id1=$($alice open_channel $bob_node 0.002 --push_amount 0.001)
+    channel_id2=$($carol open_channel $bob_node 0.002 --push_amount 0.001)
     echo "mining 3 blocks"
     new_blocks 3
     sleep 10 # time for channelDB

electrum/transaction.py

@@ -879,6 +879,14 @@ class Transaction:
         script = bitcoin.address_to_script(addr)
         return self.get_output_idxs_from_scriptpubkey(script)
 
+    def output_value_for_address(self, addr):
+        # assumes exactly one output has that address
+        for o in self.outputs():
+            if o.address == addr:
+                return o.value
+        else:
+            raise Exception('output not found', addr)
+
 
 def convert_raw_tx_to_hex(raw: Union[str, bytes]) -> str:
     """Sanitizes tx-describing input (hex/base43/base64) into

electrum/wallet.py

@@ -917,6 +917,10 @@ class Abstract_Wallet(AddressSynchronizer):
     def make_unsigned_transaction(self, *, coins: Sequence[PartialTxInput],
                                   outputs: List[PartialTxOutput], fee=None,
                                   change_addr: str = None, is_sweep=False) -> PartialTransaction:
+
+        # prevent side-effect with '!'
+        outputs = copy.deepcopy(outputs)
+
         # check outputs
         i_max = None
         for i, o in enumerate(outputs):