pytest: test for crash when we do a plugin op and a plugin has not finished init

We try to start it twice, with predictable hilarious results:

   DEBUG plugin-manager started(20701) /home/rusty/devel/cvs/lightning/tests/plugins/slow_init.py
   DEBUG lightningd(20670): Adding block 101: 0f26301caaae390d1b956c3eb73827d1f87a2af306561348045bf1313b7551b0
   INFO plugin-slow_init.py slow_init.py initializing
   DEBUG plugin-manager started(20704) /home/rusty/devel/cvs/lightning/tests/plugins/slow_init.py
   **BROKEN** lightningd(20670): FATAL SIGNAL 6 (version v0.7.1-146-g7d3b352-modded)
   **BROKEN** lightningd(20670): backtrace: common/daemon.c:45 (send_backtrace) 0x55a29c3ec539
   **BROKEN** lightningd(20670): backtrace: common/daemon.c:53 (crashdump) 0x55a29c3ec589
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281ebcf5f
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281ebced7
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281e9e534
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281e9e40e
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281eae011
   **BROKEN** lightningd(20670): backtrace: lightningd/json_stream.c:225 (json_stream_output_) 0x55a29c3bff5f
   **BROKEN** lightningd(20670): backtrace: lightningd/plugin.c:383 (plugin_write_json) 0x55a29c3e103f
   **BROKEN** lightningd(20670): backtrace: ccan/ccan/io/io.c:59 (next_plan) 0x55a29c43316b
   **BROKEN** lightningd(20670): backtrace: ccan/ccan/io/io.c:435 (io_do_always) 0x55a29c433df1
   **BROKEN** lightningd(20670): backtrace: ccan/ccan/io/poll.c:300 (handle_always) 0x55a29c435865
   **BROKEN** lightningd(20670): backtrace: ccan/ccan/io/poll.c:377 (io_loop) 0x55a29c435b3d
   **BROKEN** lightningd(20670): backtrace: lightningd/io_loop_with_timers.c:24 (io_loop_with_timers) 0x55a29c3bdfcf
   **BROKEN** lightningd(20670): backtrace: lightningd/lightningd.c:830 (main) 0x55a29c3c44b6
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x7fa281e9fb6a
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0x55a29c3ac0f9
   **BROKEN** lightningd(20670): backtrace: (null):0 ((null)) 0xffffffffffffffff

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

tests/plugins/slow_init.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python3
+from lightning import Plugin
+import time
+
+plugin = Plugin()
+
+
+@plugin.init()
+def init(options, configuration, plugin):
+    plugin.log("slow_init.py initializing")
+    time.sleep(1)
+
+
+plugin.run()

tests/test_plugin.py

@@ -90,6 +90,20 @@ def test_plugin_dir(node_factory):
     node_factory.get_node(options={'plugin-dir': plugin_dir, 'greeting': 'Mars'})
 
 
+@pytest.mark.xfail(strict=True)
+def test_plugin_slowinit(node_factory):
+    """Tests the 'plugin' RPC command when init is slow"""
+    n = node_factory.get_node()
+
+    n.rpc.plugin_start(os.path.join(os.getcwd(), "tests/plugins/slow_init.py"))
+    n.daemon.wait_for_log("slow_init.py initializing")
+
+    # It's not actually configured yet, see what happens;
+    # make sure 'rescan' and 'list' controls dont crash
+    n.rpc.plugin_rescan()
+    n.rpc.plugin_list()
+
+
 def test_plugin_command(node_factory):
     """Tests the 'plugin' RPC command"""
     n = node_factory.get_node()