Fixed handling parameters with default values in task factory constru…

…ction (#1047)

* Fixed handling default inputs in task factory construction

* Added tests.

sdk/python/kfp/components/_components.py

@@ -235,8 +235,8 @@ def create_task_from_component_and_arguments(pythonic_arguments):
     import inspect
     from . import _dynamic
 
-    #Reordering the inputs since in Python optional parameters must come after reuired parameters
-    reordered_input_list = [input for input in inputs_list if not input.optional] + [input for input in inputs_list if input.optional]
+    #Reordering the inputs since in Python optional parameters must come after required parameters
+    reordered_input_list = [input for input in inputs_list if input.default is None and not input.optional] + [input for input in inputs_list if not (input.default is None and not input.optional)]
     input_parameters  = [_dynamic.KwParameter(input_name_to_pythonic[port.name], annotation=(_try_get_object_by_name(str(port.type)) if port.type else inspect.Parameter.empty), default=port.default if port.default is not None else (None if port.optional else inspect.Parameter.empty)) for port in reordered_input_list]
     factory_function_parameters = input_parameters #Outputs are no longer part of the task factory function signature. The paths are always generated by the system.
 

sdk/python/tests/components/test_components.py

@@ -290,6 +290,49 @@ def test_optional_inputs_reordering(self):
         actual_signature = list(signature.parameters.keys())
         self.assertSequenceEqual(actual_signature, ['in1', 'in3', 'in2'], str)
 
+    def test_inputs_reordering_when_inputs_have_defaults(self):
+        '''Tests reordering of inputs with default values.
+        In python signature, optional arguments must come after the required arguments.
+        '''
+        component_text = '''\
+inputs:
+- {name: in1}
+- {name: in2, default: val}
+- {name: in3}
+implementation:
+  container:
+    image: busybox
+'''
+        task_factory1 = comp.load_component_from_text(component_text)
+        import inspect
+        signature = inspect.signature(task_factory1)
+        actual_signature = list(signature.parameters.keys())
+        self.assertSequenceEqual(actual_signature, ['in1', 'in3', 'in2'], str)
+
+    def test_inputs_reordering_stability(self):
+        '''Tests input reordering stability. Required inputs and optional/default inputs should keep the ordering.
+        In python signature, optional arguments must come after the required arguments.
+        '''
+        component_text = '''\
+inputs:
+- {name: a1}
+- {name: b1, default: val}
+- {name: a2}
+- {name: b2, optional: True}
+- {name: a3}
+- {name: b3, default: val}
+- {name: a4}
+- {name: b4, optional: True}
+implementation:
+  container:
+    image: busybox
+'''
+        task_factory1 = comp.load_component_from_text(component_text)
+        import inspect
+        signature = inspect.signature(task_factory1)
+        actual_signature = list(signature.parameters.keys())
+        self.assertSequenceEqual(actual_signature, ['a1', 'a2', 'a3', 'a4', 'b1', 'b2', 'b3', 'b4'], str)
+
     def test_missing_optional_input_value_argument(self):
         '''Missing optional inputs should resolve to nothing'''
         component_text = '''\