pyln-testing: use files for stdout and stderr, not threads.

Some flakes are caused by weird races in this code.  Plus, if we
get things to write straight to files, we might see things in
there on post-mortem which happen after the python runner exits.

It's a bit less efficient, but much simpler.  Let's see if it helps!

Some tests need a rework now, since we don't get a failure (except
eventual timeout), but they're simpler.

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

tests/test_plugin.py

@@ -94,7 +94,7 @@ def test_option_types(node_factory):
     }, expect_fail=True, may_fail=True)
 
     # the node should fail to start, and we get a stderr msg
-    assert not n.daemon.running
+    assert n.daemon.wait() == 1
     wait_for(lambda: n.daemon.is_in_stderr('bool_opt: ! does not parse as type bool'))
 
     # What happens if we give it a bad int-option?
@@ -106,7 +106,7 @@ def test_option_types(node_factory):
     }, may_fail=True, expect_fail=True)
 
     # the node should fail to start, and we get a stderr msg
-    assert not n.daemon.running
+    assert n.daemon.wait() == 1
     assert n.daemon.is_in_stderr('--int_opt: notok does not parse as type int')
 
     # Flag opts shouldn't allow any input
@@ -119,7 +119,7 @@ def test_option_types(node_factory):
     }, may_fail=True, expect_fail=True)
 
     # the node should fail to start, and we get a stderr msg
-    assert not n.daemon.running
+    assert n.daemon.wait() == 1
     assert n.daemon.is_in_stderr("--flag_opt: doesn't allow an argument")
 
     n = node_factory.get_node(options={
@@ -1500,9 +1500,10 @@ def test_libplugin(node_factory):
     l1.stop()
     l1.daemon.opts["name-deprecated"] = "test_opt"
 
-    # This actually dies while waiting for the logs.
-    with pytest.raises(ValueError):
-        l1.start()
+    l1.daemon.start(wait_for_initialized=False)
+    # Will exit with failure code.
+    assert l1.daemon.wait() == 1
+    assert l1.daemon.is_in_stderr(r"name-deprecated: deprecated option")
 
     del l1.daemon.opts["name-deprecated"]
     l1.start()
@@ -1646,24 +1647,20 @@ def test_bitcoin_backend(node_factory, bitcoind):
     # We don't start if we haven't all the required methods registered.
     plugin = os.path.join(os.getcwd(), "tests/plugins/bitcoin/part1.py")
     l1.daemon.opts["plugin"] = plugin
-    try:
-        l1.daemon.start()
-    except ValueError:
-        assert l1.daemon.is_in_log("Missing a Bitcoin plugin command")
-        # Now we should start if all the commands are registered, even if they
-        # are registered by two distincts plugins.
-        del l1.daemon.opts["plugin"]
-        l1.daemon.opts["plugin-dir"] = os.path.join(os.getcwd(),
-                                                    "tests/plugins/bitcoin/")
-        try:
-            l1.daemon.start()
-        except ValueError:
-            msg = "All Bitcoin plugin commands registered"
-            assert l1.daemon.is_in_log(msg)
-        else:
-            raise Exception("We registered all commands but couldn't start!")
-    else:
-        raise Exception("We could start without all commands registered !!")
+    l1.daemon.start(wait_for_initialized=False)
+    l1.daemon.wait_for_log("Missing a Bitcoin plugin command")
+    # Will exit with failure code.
+    assert l1.daemon.wait() == 1
+    assert l1.daemon.is_in_stderr(r"Could not access the plugin for sendrawtransaction")
+    # Now we should start if all the commands are registered, even if they
+    # are registered by two distincts plugins.
+    del l1.daemon.opts["plugin"]
+    l1.daemon.opts["plugin-dir"] = os.path.join(os.getcwd(),
+                                                "tests/plugins/bitcoin/")
+    # (it fails when it tries to use them, so startup fails)
+    l1.daemon.start(wait_for_initialized=False)
+    l1.daemon.wait_for_log("All Bitcoin plugin commands registered")
+    assert l1.daemon.wait() == 1
 
     # But restarting with just bcli is ok
     del l1.daemon.opts["plugin-dir"]
@@ -2074,73 +2071,55 @@ def test_important_plugin(node_factory):
     n = node_factory.get_node(options={"important-plugin": os.path.join(pluginsdir, "nonexistent")},
                               may_fail=True, expect_fail=True,
                               allow_broken_log=True, start=False)
-    n.daemon.start(wait_for_initialized=False, stderr=subprocess.PIPE)
-    wait_for(lambda: not n.daemon.running)
-
+    n.daemon.start(wait_for_initialized=False)
+    # Will exit with failure code.
+    assert n.daemon.wait() == 1
     assert n.daemon.is_in_stderr(r"error starting plugin '.*nonexistent'")
 
-    # We use a log file, since our wait_for_log is unreliable when the
-    # daemon actually dies.
-    def get_logfile_match(logpath, regex):
-        if not os.path.exists(logpath):
-            return None
-        with open(logpath, 'r') as f:
-            for line in f.readlines():
-                m = re.search(regex, line)
-                if m is not None:
-                    return m
-        return None
-
-    logpath = os.path.join(n.daemon.lightning_dir, TEST_NETWORK, 'logfile')
-    n.daemon.opts['log-file'] = 'logfile'
-
     # Check we exit if the important plugin dies.
     n.daemon.opts['important-plugin'] = os.path.join(pluginsdir, "fail_by_itself.py")
 
     n.daemon.start(wait_for_initialized=False)
-    wait_for(lambda: not n.daemon.running)
-
-    assert get_logfile_match(logpath,
-                             r'fail_by_itself.py: Plugin marked as important, shutting down lightningd')
-    os.remove(logpath)
+    # Will exit with failure code.
+    assert n.daemon.wait() == 1
+    n.daemon.wait_for_log(r'fail_by_itself.py: Plugin marked as important, shutting down lightningd')
 
     # Check if the important plugin is disabled, we run as normal.
     n.daemon.opts['disable-plugin'] = "fail_by_itself.py"
-    del n.daemon.opts['log-file']
     n.daemon.start()
     # Make sure we can call into a plugin RPC (this is from `bcli`) even
     # if fail_by_itself.py is disabled.
     n.rpc.call("estimatefees", {})
-    # Make sure we are still running.
-    assert n.daemon.running
     n.stop()
 
     # Check if an important plugin dies later, we fail.
     del n.daemon.opts['disable-plugin']
-    n.daemon.opts['log-file'] = 'logfile'
     n.daemon.opts['important-plugin'] = os.path.join(pluginsdir, "suicidal_plugin.py")
 
-    n.daemon.start(wait_for_initialized=False)
-    wait_for(lambda: get_logfile_match(logpath, "Server started with public key"))
+    n.start()
 
     with pytest.raises(RpcError):
         n.rpc.call("die", {})
 
-    wait_for(lambda: not n.daemon.running)
-    assert get_logfile_match(logpath, 'suicidal_plugin.py: Plugin marked as important, shutting down lightningd')
-    os.remove(logpath)
+    # Should exit with exitcode 1
+    n.daemon.wait_for_log('suicidal_plugin.py: Plugin marked as important, shutting down lightningd')
+    assert n.daemon.wait() == 1
+    n.stop()
 
     # Check that if a builtin plugin dies, we fail.
-    n.daemon.start(wait_for_initialized=False)
-
-    wait_for(lambda: get_logfile_match(logpath, r'.*started\(([0-9]*)\).*plugins/pay'))
-    pidstr = get_logfile_match(logpath, r'.*started\(([0-9]*)\).*plugins/pay').group(1)
+    start = n.daemon.logsearch_start
+    n.start()
+    # Reset logsearch_start, since this will predate message that start() looks for.
+    n.daemon.logsearch_start = start
+    line = n.daemon.wait_for_log(r'.*started\([0-9]*\).*plugins/pay')
+    pidstr = re.search(r'.*started\(([0-9]*)\).*plugins/pay', line).group(1)
 
     # Kill pay.
     os.kill(int(pidstr), signal.SIGKILL)
-    wait_for(lambda: not n.daemon.running)
-
-    assert get_logfile_match(logpath, 'pay: Plugin marked as important, shutting down lightningd')
+    n.daemon.wait_for_log('pay: Plugin marked as important, shutting down lightningd')
+    # Should exit with exitcode 1
+    assert n.daemon.wait() == 1
+    n.stop()
 
 
 @pytest.mark.developer("tests developer-only option.")