pylightning: translate msat input to class Millisatoshi

Rather than using LightningJSONDecoder's implicit "field name and
value ends in msat, try converting to Millisatoshi", we do it to
parameters using type annotations.

If you had a parameter which was an array or dict itself, we don't
delve into that, but that's probably OK.

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

contrib/pylightning/lightning/plugin.py

@@ -1,6 +1,6 @@
 from collections import OrderedDict
 from enum import Enum
-from lightning import LightningRpc
+from lightning import LightningRpc, Millisatoshi
 from threading import RLock
 
 import inspect
@@ -293,7 +293,11 @@ def _exec_func(self, func, request):
         if isinstance(params, dict):
             for k, v in params.items():
                 if k in arguments:
-                    arguments[k] = v
+                    # Explicitly (try to) interpret as Millisatoshi if annotated
+                    if func.__annotations__.get(k) == Millisatoshi:
+                        arguments[k] = Millisatoshi(v)
+                    else:
+                        arguments[k] = v
                 else:
                     kwargs[k] = v
         else:
@@ -305,7 +309,10 @@ def _exec_func(self, func, request):
 
                 if pos < len(params):
                     # Apply positional args if we have them
-                    arguments[k] = params[pos]
+                    if func.__annotations__.get(k) == Millisatoshi:
+                        arguments[k] = Millisatoshi(params[pos])
+                    else:
+                        arguments[k] = params[pos]
                 elif sig.parameters[k].default is inspect.Signature.empty:
                     # This is a positional arg with no value passed
                     raise TypeError("Missing required parameter: %s" % sig.parameters[k])
@@ -406,6 +413,8 @@ def _multi_dispatch(self, msgs):
         Returns the last partial message that was not complete yet.
         """
         for payload in msgs[:-1]:
+            # Note that we use function annotations to do Millisatoshi conversions
+            # in _exec_func, so we don't use LightningJSONDecoder here.
             request = self._parse_request(json.loads(payload))
 
             # If this has an 'id'-field, it's a request and returns a

tests/test_plugin.py

@@ -34,7 +34,6 @@ def test_option_passthrough(node_factory):
     n.stop()
 
 
-@pytest.mark.xfail(strict=True)
 def test_millisatoshi_passthrough(node_factory):
     """ Ensure that Millisatoshi arguments and return work.
     """