From 3d6c4e93b3d4f5e50a0c28ea07780cbb022d6565 Mon Sep 17 00:00:00 2001
From: Christian Decker <decker.christian@gmail.com>
Date: Wed, 9 Sep 2020 14:15:01 +0200
Subject: [PATCH] pytest: Add a test to reproduce #3748

---
 tests/plugins/htlc_accepted-crash.py | 14 +++++++++++++
 tests/test_plugin.py                 | 30 ++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100755 tests/plugins/htlc_accepted-crash.py

diff --git a/tests/plugins/htlc_accepted-crash.py b/tests/plugins/htlc_accepted-crash.py
new file mode 100755
index 000000000..266174300
--- /dev/null
+++ b/tests/plugins/htlc_accepted-crash.py
@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+from pyln.client import Plugin
+
+
+plugin = Plugin()
+
+
+@plugin.hook('htlc_accepted')
+def on_htlc_accepted(plugin, **kwargs):
+    plugin.log("Crashing on purpose...")
+    raise ValueError()
+
+
+plugin.run()
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index f12e67b3c..9057b041b 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -1858,3 +1858,33 @@ def test_important_plugin(node_factory):
 def test_dev_builtin_plugins_unimportant(node_factory):
     n = node_factory.get_node(options={"dev-builtin-plugins-unimportant": None})
     n.rpc.plugin_stop(plugin="pay")
+
+
+@pytest.mark.xfail(strict=True)
+def test_htlc_accepted_hook_crash(node_factory, executor):
+    """Test that we do not hang incoming HTLCs if the hook plugin crashes.
+
+    Reproduces #3748.
+    """
+    plugin = os.path.join(os.getcwd(), 'tests/plugins/htlc_accepted-crash.py')
+    l1 = node_factory.get_node()
+    l2 = node_factory.get_node(
+        options={'plugin': plugin},
+        allow_broken_log=True
+    )
+    l1.connect(l2)
+    l1.fund_channel(l2, 10**6)
+
+    i = l2.rpc.invoice(500, "crashpls", "crashpls")['bolt11']
+
+    # This should still succeed
+
+    f = executor.submit(l1.rpc.pay, i)
+
+    l2.daemon.wait_for_log(r'Crashing on purpose...')
+    l2.daemon.wait_for_log(
+        r'Hook handler for htlc_accepted failed with an exception.'
+    )
+
+    with pytest.raises(RpcError, match=r'failed: WIRE_TEMPORARY_NODE_FAILURE'):
+        f.result(10)