tests: add Carl Dong's example exhaustive zeroconf channel pay test.

Modifications from issue #5803 to work here:

1. import json
2. Add xfail
3. Increase channel sizes by 10x so we can open them
4. Fix plugin path

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_pay.py

@@ -10,6 +10,7 @@ from utils import (
 )
 import copy
 import os
+import json
 import pytest
 import random
 import re
@@ -5302,3 +5303,115 @@ def test_payerkey(node_factory):
     for n, k in zip(nodes, expected_keys):
         b12 = n.rpc.createinvoicerequest('lnr1qqgz2d7u2smys9dc5q2447e8thjlgq3qqc3xu3s3rg94nj40zfsy866mhu5vxne6tcej5878k2mneuvgjy8ssqvepgz5zsjrg3z3vggzvkm2khkgvrxj27r96c00pwl4kveecdktm29jdd6w0uwu5jgtv5v9qgqxyfhyvyg6pdvu4tcjvpp7kkal9rp57wj7xv4pl3ajku70rzy3pu', False)['bolt12']
         assert n.rpc.decode(b12)['invreq_payer_id'] == k
+
+
+@pytest.mark.xfail
+@pytest.mark.parametrize("payment_method", ["pay", "getroute_sendpay"])
+@pytest.mark.parametrize("confirm_zeroconf_channel", [False, True], ids=["no_confirm_zeroconf", "yes_confirm_zeroconf"])
+@pytest.mark.parametrize("open_existing_normal_channel", [False, True], ids=["zeroconf_only", "add_existing_normal"])
+def test_cln_sendpay_weirdness(bitcoind, node_factory, open_existing_normal_channel, payment_method, confirm_zeroconf_channel):
+    # 0. Setup
+
+    # 0.1 Setup the payer node
+    l1 = node_factory.get_node()
+    print("CARL: DONE l1 setup")
+
+    # 0.2 Setup the receiver node
+    zeroconf_plugin = Path(__file__).parent / "plugins" / "zeroconf-selective.py"
+    l2 = node_factory.get_node(
+        options={
+            'plugin': zeroconf_plugin,
+            'zeroconf-allow': l1.info['id'],
+        },
+    )
+    print("CARL: DONE l2 setup")
+
+    # 0.3 Connect the nodes
+    l1.connect(l2)
+
+    # 0.4 Optionally open a normal channel l1 -> l2 if we're testing that
+    if open_existing_normal_channel:
+        normal_sats = 200_000
+        print("CARL: Opening normal channel btw l1 and l2")
+        l1.fundchannel(l2, amount=normal_sats)  # This will mine a block!
+        print("CARL: DONE: Opening normal channel btw l1 and l2")
+
+    # 0.5 Define a helper that syncs nodes to bitcoind and returns the blockheight
+    def synced_blockheight(nodes):
+        blockcount = bitcoind.rpc.getblockcount()
+        print(f"CARL: bitcoind blockcount {blockcount}")
+        wait_for(lambda: all([node.rpc.getinfo()['blockheight'] == blockcount for node in nodes]))
+        return blockcount
+
+
+    # 1. Open a zeoconf channel l1 -> l2
+    zeroconf_sats = 1_000_000
+
+    # 1.1 Add funds to l1's wallet for the channel open
+    l1.fundwallet(zeroconf_sats * 2)  # This will mine a block!
+    fundchannel_blockheight = synced_blockheight([l1, l2])
+    print(f"CARL: blockheight before fundchannel: {fundchannel_blockheight}")
+
+    # 1.2 Open the zeroconf channel
+    print("CARL: Opening zeroconf channel btw l1 and l2")
+    l1.rpc.fundchannel(l2.info['id'], zeroconf_sats, announce=False, mindepth=0)
+    print("CARL: DONE Opening zeroconf channel btw l1 and l2")
+
+    # 1.2 Optionally generate a block to confirm the zeroconf channel if we're testing that
+    if confirm_zeroconf_channel:
+        bitcoind.generate_block(1)
+        l1.daemon.wait_for_log(r'Funding tx [a-f0-9]{64} depth 1 of 0')
+        l2.daemon.wait_for_log(r'Funding tx [a-f0-9]{64} depth 1 of 0')
+
+    # 1.3 Wait until the channel becomes active
+    print("CARL: Waiting until channel becomes active")
+    num_channels = 4 if open_existing_normal_channel else 2
+    wait_for(lambda: len(l1.rpc.listchannels()['channels']) == num_channels)
+    wait_for(lambda: len(l2.rpc.listchannels()['channels']) == num_channels)
+    print("CARL: DONE Waiting until channel becomes active")
+
+    # 1.4 Print out channels as seen from both nodes
+    channels = l1.rpc.listchannels()
+    print(f"CARL: l1's channels after zeroconf channel open:\n{json.dumps(channels, indent=4)}")
+    channels = l2.rpc.listchannels()
+    print(f"CARL: l2's channels after zeroconf channel open:\n{json.dumps(channels, indent=4)}")
+
+
+    # 2. Have l2 generate an invoice to be paid
+    invoice_sats = 500_000
+    inv = l2.rpc.invoice(invoice_sats * 1_000, "test", "test")
+    psecret = l1.rpc.decodepay(inv['bolt11'])['payment_secret']
+    rhash = inv['payment_hash']
+
+
+    # 3. Send a payment over the zeroconf channel
+    riskfactor=0
+
+    ## 3.1 Sanity check that we're at the block height we expect
+    payment_blockheight = synced_blockheight([l1, l2])
+    print(f"CARL: blockheight before payment: {payment_blockheight}")
+    if confirm_zeroconf_channel:
+        assert(fundchannel_blockheight + 1 == payment_blockheight)
+    else:
+        assert(fundchannel_blockheight == payment_blockheight)
+
+    if payment_method == "getroute_sendpay":
+        ## 3.2 Get a route to l2
+        route = l1.rpc.getroute(l2.info['id'], 1, riskfactor)['route']
+        print(f"CARL: l1's route to l2 for 1sat: {json.dumps(route, indent=4)}")
+        route = l1.rpc.getroute(l2.info['id'], invoice_sats * 1_000, riskfactor)['route']
+        print(f"CARL: l1's route to l2 for invoice amount {invoice_sats * 1_000}msat: {json.dumps(route, indent=4)}")
+
+        ## 3.3 Send the payment via SENDPAY
+        print("CARL: SENDPAY via l1's route to l2 for invoice")
+        l1.rpc.sendpay(route, rhash, payment_secret=psecret, bolt11=inv['bolt11'])
+        result = l1.rpc.waitsendpay(rhash)
+        assert(result.get('status') == 'complete')
+        print("CARL: DONE: SENDPAY via l1's route to l2 for invoice")
+    elif payment_method == "pay":
+        ## 3.2 Alternatively, send the payment via PAY
+        print("CARL: PAY via l1's route to l2 for invoice")
+        l1.rpc.pay(inv['bolt11'], riskfactor=riskfactor)
+        print("CARL: DONE: PAY via l1's route to l2 for invoice")
+    else:
+        raise