regtests: add test "swapserver_server_skip_onchain_funding"

trying to reproduce #9980

Author: SomberNight

electrum/simple_config.py

@@ -891,6 +891,7 @@ def __setattr__(self, name, value):
     # connect to remote submarine swap server
     SWAPSERVER_URL = ConfigVar('swapserver_url', default='', type_=str)
     TEST_SWAPSERVER_REFUND = ConfigVar('test_swapserver_refund', default=False, type_=bool)
+    TEST_SWAPSERVER_SKIP_ONCHAIN_FUNDING = ConfigVar('test_swapserver_skip_onchain_funding', default=False, type_=bool)
     SWAPSERVER_NPUB = ConfigVar('swapserver_npub', default=None, type_=str)
     SWAPSERVER_POW_TARGET = ConfigVar('swapserver_pow_target', default=30, type_=int)
 

electrum/submarine_swaps.py

@@ -512,6 +512,8 @@ async def hold_invoice_callback(self, payment_hash: bytes) -> None:
         key = payment_hash.hex()
         if swap := self._swaps.get(key):
             if not swap.is_funded():
+                if self.network.config.TEST_SWAPSERVER_SKIP_ONCHAIN_FUNDING:  # for testing
+                    return
                 output = self.create_funding_output(swap)
                 self.wallet.txbatcher.add_payment_output('swaps', output)
                 swap._payment_pending = True

tests/regtest.py

@@ -107,6 +107,9 @@ def test_swapserver_forceclose(self):
     def test_swapserver_refund(self):
         self.run_shell(['swapserver_refund'])
 
+    def test_swapserver_server_skip_onchain_funding(self):
+        self.run_shell(['swapserver_server_skip_onchain_funding'])
+
 
 
 class TestLightningWatchtower(TestLightning):

tests/regtest/regtest.sh

@@ -308,6 +308,49 @@ if [[ $1 == "swapserver_refund" ]]; then
 fi
 
 
+if [[ $1 == "swapserver_server_skip_onchain_funding" ]]; then
+    # Alice starts reverse-swap with Bob.
+    # Alice sends hold-HTLCs via LN. Bob does NOT fund locking script onchain.
+    # After a while, Alice requests Bob to force-close chan, and Bob does.
+    # Alice will broadcast HTLC-timeout tx to reclaim the swap amount from Bob's commitment tx.
+    $bob setconfig test_swapserver_skip_onchain_funding true
+    wait_for_balance alice 1
+    echo "alice opens channel"
+    bob_node=$($bob nodeid)
+    channel=$($alice open_channel $bob_node 0.15 --password='')
+    chan_funding_txid=$(echo "$channel" | cut -d ":" -f 1)
+    chan_funding_outidx=$(echo "$channel" | cut -d ":" -f 2)
+    new_blocks 3
+    wait_until_channel_open alice
+    echo "alice initiates swap"
+    dryrun=$($alice reverse_swap 0.02 dryrun)
+    onchain_amount=$(echo $dryrun| jq -r ".onchain_amount")
+    # Alice starts a reverse-swap, but will time out waiting for Bob's swap-funding-tx to appear in mempool.
+    $alice setconfig timeout 10
+    set +e
+    swap=$($alice reverse_swap 0.02 $onchain_amount)
+    set -e
+    $alice unsetconfig timeout
+    # After a while, Alice gets impatient and gets Bob to close the channel.
+    new_blocks 20
+    $alice request_force_close $channel
+    wait_until_spent $chan_funding_txid $chan_funding_outidx
+    new_blocks 1
+    wait_until_channel_closed alice
+    ctx_id=$($alice list_channels | jq -r ".[0].closing_txid")
+    # need more blocks to reach CLTV of HTLC-output in ctx
+    new_blocks 130
+    if [ $TEST_ANCHOR_CHANNELS = True ] ; then
+        htlc_output_index=3  # FIXME index depends on Alice not using MPP
+    else
+        htlc_output_index=1
+    fi
+    wait_until_spent $ctx_id $htlc_output_index
+    new_blocks 1
+    wait_for_balance alice 0.997
+fi
+
+
 if [[ $1 == "extract_preimage" ]]; then
     # Alice sends htlc1 to Bob.  Bob sends htlc2 to Alice.
     # Neither one of them settles, they hold the htlcs, and Bob force-closes.