events use different approach to define if event should be passed to callback

openpype/lib/events.py

@@ -74,22 +74,52 @@ class EventCallback(object):
                 "Registered callback is not callable. \"{}\""
             ).format(str(func)))
 
-        # Collect additional data about function
-        #   - name
-        #   - path
-        #   - if expect argument or not
+        # Collect function name and path to file for logging
         func_name = func.__name__
         func_path = os.path.abspath(inspect.getfile(func))
+
+        # Get expected arguments from function spec
+        # - positional arguments are always preferred
+        expect_args = False
+        expect_kwargs = False
+        fake_event = "fake"
         if hasattr(inspect, "signature"):
+            # Python 3 using 'Signature' object where we try to bind arg
+            #   or kwarg. Using signature is recommended approach based on
+            #   documentation.
             sig = inspect.signature(func)
-            expect_args = len(sig.parameters) > 0
+            try:
+                sig.bind(fake_event)
+                expect_args = True
+            except TypeError:
+                pass
+
+            try:
+                sig.bind(event=fake_event)
+                expect_kwargs = True
+            except TypeError:
+                pass
+
         else:
-            expect_args = len(inspect.getargspec(func)[0]) > 0
+            # In Python 2 'signature' is not available so 'getcallargs' is used
+            # - 'getcallargs' is marked as deprecated since Python 3.0
+            try:
+                inspect.getcallargs(func, fake_event)
+                expect_args = True
+            except TypeError:
+                pass
+
+            try:
+                inspect.getcallargs(func, event=fake_event)
+                expect_kwargs = True
+            except TypeError:
+                pass
 
         self._func_ref = func_ref
         self._func_name = func_name
         self._func_path = func_path
         self._expect_args = expect_args
+        self._expect_kwargs = expect_kwargs
         self._ref_valid = func_ref is not None
         self._enabled = True
 
@@ -157,6 +187,10 @@ class EventCallback(object):
             try:
                 if self._expect_args:
                     callback(event)
+
+                elif self._expect_kwargs:
+                    callback(event=event)
+
                 else:
                     callback()