avoid infinite recursion on unkown attribute access in GenericActors. (…

…#647)

* fix: avoid infinite recursion on attribute access in GenericActors.

this was triggered by sphinx autodoc use of inspect.signature that tried to
access the missing `__signature__` attribute on GenericActors

* style: fix linter errors

docs/source/conf.py

@@ -18,11 +18,11 @@
 
 import alabaster  # noqa
 
-import dramatiq  # noqa
-
 sys.path.insert(0, os.path.abspath('../..'))
 sys.path.insert(0, os.path.abspath('./'))
 
+import dramatiq  # noqa
+
 
 # -- General configuration ------------------------------------------------
 

dramatiq/generic.py

@@ -40,6 +40,9 @@ def __new__(metacls, name, bases, attrs):
         return clazz
 
     def __getattr__(cls, name):
+        if "__actor__" not in cls.__dict__:
+            # avoid infinite recursion on GenericActor
+            raise AttributeError(f"type object {cls.__name__!r} has no attribute {name!r}")
         return getattr(cls.__actor__, name)
 
 

tests/test_generic_actors.py

@@ -117,3 +117,8 @@ def perform(self):
 
     # And the actor registry should be called with CustomActor
     actor_registry.assert_called_once_with(CustomActor)
+
+
+def test_getattr_generic_actor():
+    with pytest.raises(AttributeError):
+        dramatiq.GenericActor.missing_property