feat: Allow sending and receiving messages through the runner

This commit marks the first step in the lnprototest
refactoring process, aimed at writing more readable
tests with the runner.

With this commit, it becomes possible to write tests
similar to the following example.

```
def test_v2_init_is_first_msg(runner: Runner, namespaceoverride: Any) -> None:
    """Tests workflow

    runner --- connect ---> ln node
    runner <-- init ------ ln node
    """
    runner.start()

    runner.connect(None, connprivkey="03")
    init_msg = runner.recv_msg()
    assert (
        init_msg.messagetype.number == 16
    ), f"received not an init msg but: {init_msg.to_str()}"

    runner.stop()
```

Signed-off-by: Vincenzo Palazzo <[email protected]>

Author: vincenzopalazzo

lnprototest/clightning/clightning.py

@@ -198,14 +198,14 @@ def restart(self) -> None:
         self.bitcoind.restart()
         self.start(also_bitcoind=False)
 
-    def connect(self, _: Event, connprivkey: str) -> None:
-        self.add_conn(
-            RunnerConn(
-                connprivkey,
-                "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798",
-                self.lightning_port,
-            )
+    def connect(self, _: Event, connprivkey: str) -> RunnerConn:
+        conn = RunnerConn(
+            connprivkey,
+            "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798",
+            self.lightning_port,
         )
+        self.add_conn(conn)
+        return conn
 
     def getblockheight(self) -> int:
         return self.bitcoind.rpc.getblockcount()

lnprototest/event.py

@@ -1,4 +1,3 @@
-#! /usr/bin/python3
 import logging
 import traceback
 import collections

lnprototest/runner.py

@@ -1,3 +1,4 @@
+import io
 import logging
 import shutil
 import tempfile
@@ -6,6 +7,7 @@
 import functools
 
 import pyln
+from pyln.proto.message import Message
 
 from abc import ABC, abstractmethod
 from typing import Dict, Optional, List, Union, Any, Callable
@@ -15,6 +17,7 @@
 from .event import Event, MustNotMsg, ExpectMsg
 from .utils import privkey_expand
 from .keyset import KeySet
+from .namespace import namespace
 
 
 class Conn(object):
@@ -155,6 +158,28 @@ def is_running(self) -> bool:
     def connect(self, event: Event, connprivkey: str) -> None:
         pass
 
+    def send_msg(self, msg: Message) -> None:
+        """Send a message through the last connection"""
+        missing = msg.missing_fields()
+        if missing:
+            raise SpecFileError(self, "Missing fields {}".format(missing))
+        binmsg = io.BytesIO()
+        msg.write(binmsg)
+        self.last_conn.connection.send_message(msg.getvalue())
+
+    def recv_msg(
+        self, timeout: int = 1000, skip_filter: Optional[int] = None
+    ) -> Message:
+        """Listen on the connection for incoming message.
+
+        If the {skip_filter} is specified, the message that
+        match the filters are skipped.
+        """
+        raw_msg = self.last_conn.connection.read_message()
+        msg = Message.read(namespace(), io.BytesIO(raw_msg))
+        self.add_stash(msg.messagetype.name, msg)
+        return msg
+
     @abstractmethod
     def check_final_error(
         self,

tests/test_v2_bolt1-01-init.py

@@ -0,0 +1,20 @@
+from typing import Any
+
+from lnprototest.runner import Runner
+
+
+def test_v2_init_is_first_msg(runner: Runner, namespaceoverride: Any) -> None:
+    """Tests workflow
+
+    runner --- connect ---> ln node
+    runner <-- init ------ ln node
+    """
+    runner.start()
+
+    runner.connect(None, connprivkey="03")
+    init_msg = runner.recv_msg()
+    assert (
+        init_msg.messagetype.number == 16
+    ), f"received not an init msg but: {init_msg.to_str()}"
+
+    runner.stop()