renepay: add command notifications

These show that we should clean up our notes.  Here's the result from test_hardmpp:

# we have computed a set of 1 flows with probability 0.328, fees 0msat and delay 23
# No MPP, so added 0msat shadow fee
# Shadow route on flow 0/1 added 0 block delay. now 5
# sendpay flow groupid=1, partid=1, delivering=1800000000msat, probability=0.328
# Update chan knowledge scid=103x2x0, dir=0: [0msat,1799999999msat]
# onion error WIRE_TEMPORARY_CHANNEL_FAILURE from node #1 103x2x0: failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# we have computed a set of 2 flows with probability 0.115, fees 0msat and delay 23
# Shadow route on flow 0/2 added 0 block delay. now 5
# Shadow route on flow 1/2 added 0 block delay. now 5
# sendpay flow groupid=1, partid=3, delivering=500000000msat, probability=0.475
# sendpay flow groupid=1, partid=2, delivering=1300000000msat, probability=0.242
# Update chan knowledge scid=103x2x0, dir=0: [0msat,1299999999msat]
# onion error WIRE_TEMPORARY_CHANNEL_FAILURE from node #1 103x2x0: failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# we have computed a set of 2 flows with probability 0.084, fees 0msat and delay 23
# Shadow route on flow 0/2 added 0 block delay. now 5
# Shadow route on flow 1/2 added 0 block delay. now 5
# sendpay flow groupid=1, partid=5, delivering=260000000msat, probability=0.467
# sendpay flow groupid=1, partid=4, delivering=1040000000msat, probability=0.179
# Update chan knowledge scid=103x2x0, dir=0: [0msat,1039999999msat]
# onion error WIRE_TEMPORARY_CHANNEL_FAILURE from node #1 103x2x0: failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# we have computed a set of 2 flows with probability 0.052, fees 0msat and delay 23
# Shadow route on flow 0/2 added 0 block delay. now 5
# Shadow route on flow 1/2 added 0 block delay. now 5
# sendpay flow groupid=1, partid=7, delivering=120000000msat, probability=0.494
# sendpay flow groupid=1, partid=6, delivering=920000000msat, probability=0.105

Ideally it would look something like:

# Computed 1 flows, probability=0.328:
#  Flow 1: 103x2x0 1800000000msat fee=0msat probability=0.328 shadow=+0msat/0blocks
#  Flow 1: FAIL: TEMPORARY_CHANNEL_FAILURE for 103x2x0.
# Computed 2 flows, probability=0.115:
#  Flow 2: XXX->XXX 1300000000msat fee=XXX, probability=0.475 shadow=+0msat/0blocks
#  Flow 3: XXX->XXX 500000000msat fee=XXX, probability=0.475 shadow=+0msat/0blocks
#  Flow 2: FAIL: TEMPORARY_CHANNEL_FAILURE from node #1 103x2x0
# Computed 2 flows (3 total), probability=0.084, fee=0msat, delay=23
...
#  Flow 4: SUCCESS, 2 in progress should succeed soon.

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

plugins/renepay/payment.c

@@ -108,6 +108,9 @@ void payment_note(struct payment *p, const char *fmt, ...)
 	va_end(ap);
 	tal_arr_expand(&p->paynotes, str);
 	debug_info("%s",str);
+
+	if (p->cmd)
+		plugin_notify_message(p->cmd, LOG_INFORM, "%s", str);
 }
 
 void payment_assert_delivering_incomplete(const struct payment *p)

tests/test_renepay.py

@@ -1,10 +1,11 @@
 from fixtures import *  # noqa: F401,F403
 from pyln.client import RpcError, Millisatoshi
-from utils import only_one, wait_for, mine_funding_to_announce, sync_blockheight
+from utils import only_one, wait_for, mine_funding_to_announce, sync_blockheight, TEST_NETWORK
 import pytest
 import random
 import time
 import json
+import subprocess
 
 
 def test_simple(node_factory):
@@ -309,8 +310,19 @@ def test_hardmpp(node_factory):
         print(json.dumps(l3.rpc.listpeerchannels()), file=f)
 
     inv2 = l6.rpc.invoice("1800000sat", "inv2", 'description')
-    l1.rpc.call(
-        'renepay', {'invstring': inv2['bolt11']})
+
+    out = subprocess.check_output(['cli/lightning-cli',
+                                   '--network={}'.format(TEST_NETWORK),
+                                   '--lightning-dir={}'
+                                   .format(l1.daemon.lightning_dir),
+                                   '-k',
+                                   'renepay', 'invstring={}'.format(inv2['bolt11'])]).decode('utf-8')
+    lines = out.split('\n')
+    # First comes commentry
+    assert any([l.startswith('#') for l in lines])
+
+    # Now comes JSON
+    json.loads("".join([l for l in lines if not l.startswith('#')]))
     l1.wait_for_htlcs()
     invoice = only_one(l6.rpc.listinvoices('inv2')['invoices'])
     assert isinstance(invoice['amount_received_msat'], Millisatoshi)