pytest: add test for db constraint failure

wallet_channel_insert: UNIQUE constraint failed: peers.node_id
lightningd: Fatal signal 6 (version v0.6.3rc1-202-g4c8cb98)
0x555625b14261 crashdump
	common/daemon.c:40
0x7f8f7400e0ff ???
	???:0
0x7f8f7400e077 ???
	???:0
0x7f8f73fef534 ???
	???:0
0x555625af34f2 fatal
	lightningd/log.c:624
0x555625b3dd96 db_exec_prepared_
	wallet/db.c:448
0x555625b44fcd wallet_channel_insert
	wallet/wallet.c:1067
0x555625af64f7 wallet_commit_channel
	lightningd/opening_control.c:229
0x555625af6e86 opening_funder_finished
	lightningd/opening_control.c:394
0x555625af7bfa openingd_msg
	lightningd/opening_control.c:714
0x555625b0d421 sd_msg_read
	lightningd/subd.c:474
0x555625b0cd3b read_fds
	lightningd/subd.c:302
0x555625b548d3 next_plan
	ccan/ccan/io/io.c:59
0x555625b553ef do_plan
	ccan/ccan/io/io.c:395
0x555625b5542d io_ready
	ccan/ccan/io/io.c:405
0x555625b5700e io_loop
	ccan/ccan/io/poll.c:310
0x555625af1562 main
	lightningd/lightningd.c:827
0x7f8f73ff109a ???
	???:0
0x555625adaad9 ???
	???:0
0xffffffffffffffff ???
	???:0
Log dumped in crash.log.20190220020526

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

tests/test_connection.py

@@ -1508,3 +1508,50 @@ def test_restart_many_payments(node_factory):
     # Wait for them to finish.
     for n in innodes:
         wait_for(lambda: 'pending' not in [p['status'] for p in n.rpc.listpayments()['payments']])
+
+
+@pytest.mark.xfail(strict=True)
+@unittest.skipIf(not DEVELOPER, "need dev-disconnect")
+def test_fail_unconfirmed(node_factory, bitcoind, executor):
+    """Test that if we crash with an unconfirmed connection to a known
+    peer, we don't have a dangling peer in db"""
+    # = is a NOOP disconnect, but sets up file.
+    l1 = node_factory.get_node(disconnect=['=WIRE_OPEN_CHANNEL'])
+    l2 = node_factory.get_node()
+
+    # First one, we close by mutual agreement.
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fund_channel(l2, 200000, wait_for_active=True)
+    l1.rpc.close(l2.info['id'])
+
+    # Make sure it's closed
+    l1.wait_for_channel_onchain(l2.info['id'])
+    bitcoind.generate_block(1)
+    l1.daemon.wait_for_log('State changed from CLOSINGD_COMPLETE to FUNDING_SPEND_SEEN')
+
+    l1.stop()
+    # Mangle disconnect file so this time it blackholes....
+    with open(l1.daemon.disconnect_file, "w") as f:
+        f.write("0WIRE_OPEN_CHANNEL\n")
+    l1.start()
+
+    # Now we establish a new channel, which gets stuck.
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fundwallet(10**7)
+    executor.submit(l1.rpc.fundchannel, l2.info['id'], 100000)
+
+    l1.daemon.wait_for_log("dev_disconnect")
+
+    # Now complete old channel.
+    bitcoind.generate_block(100)
+    l1.daemon.wait_for_log('onchaind complete, forgetting peer')
+
+    # And crash l1, which is stuck.
+    l1.daemon.kill()
+
+    # Now, restart and see if it can connect OK.
+    del l1.daemon.opts['dev-disconnect']
+    l1.start()
+
+    l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
+    l1.fund_channel(l2, 200000, wait_for_active=True)