chore (sdk.v2): Error out on using InputPath placeholder for artifacts require importer. (#4929)

* throw error on importer-inputpath combination

* address review comments

sdk/python/kfp/v2/compiler/compiler_test.py

@@ -289,8 +289,7 @@ class CompilerTest(unittest.TestCase):
       component_op(value=value)
 
     with self.assertRaisesRegex(
-        TypeError,
-        ' type "Float" cannot be paired with InputUriPlaceholder.'):
+        TypeError, ' type "Float" cannot be paired with InputUriPlaceholder.'):
       compiler.Compiler().compile(
           pipeline_func=my_pipeline,
           pipeline_root='dummy',
@@ -351,6 +350,7 @@ class CompilerTest(unittest.TestCase):
           """)
 
   def test_compile_pipeline_with_invalid_name_should_raise_error(self):
+
     def my_pipeline():
       pass
 
@@ -363,6 +363,52 @@ class CompilerTest(unittest.TestCase):
           pipeline_root='dummy',
           output_path='output.json')
 
+  def test_compile_pipeline_with_importer_on_inputpath_should_raise_error(self):
+
+    # YAML componet authoring
+    component_op = components.load_component_from_text("""
+        name: compoent with misused placeholder
+        inputs:
+        - {name: model, type: Model}
+        implementation:
+          container:
+            image: dummy
+            args:
+            - {inputPath: model}
+        """)
+
+    @dsl.pipeline(name='my-component')
+    def my_pipeline(model):
+      component_op(model=model)
+
+    with self.assertRaisesRegex(
+        TypeError,
+        'Input "model" with type "Model" is not connected to any upstream '
+        'output. However it is used with InputPathPlaceholder.'):
+      compiler.Compiler().compile(
+          pipeline_func=my_pipeline,
+          pipeline_root='dummy',
+          output_path='output.json')
+
+    # Python function based component authoring
+    def my_component(datasets: components.InputPath('Datasets')):
+      pass
+
+    component_op = components.create_component_from_func(my_component)
+
+    @dsl.pipeline(name='my-component')
+    def my_pipeline(datasets):
+      component_op(datasets=datasets)
+
+    with self.assertRaisesRegex(
+        TypeError,
+        'Input "datasets" with type "Datasets" is not connected to any upstream '
+        'output. However it is used with InputPathPlaceholder.'):
+      compiler.Compiler().compile(
+          pipeline_func=my_pipeline,
+          pipeline_root='dummy',
+          output_path='output.json')
+
 
 if __name__ == '__main__':
   unittest.main()

sdk/python/kfp/v2/dsl/component_bridge.py

@@ -147,6 +147,15 @@ def create_container_op_from_component_and_arguments(
       raise TypeError(
           'Input "{}" with type "{}" cannot be paired with InputPathPlaceholder.'
           .format(input_key, inputs_dict[input_key].type))
+    elif input_key in importer_spec:
+      raise TypeError(
+          'Input "{}" with type "{}" is not connected to any upstream output. '
+          'However it is used with InputPathPlaceholder. '
+          'If you want to import an existing artifact using a system-connected '
+          'importer node, use InputUriPlaceholder instead. '
+          'Or if you just want to pass a string parameter, use string type and '
+          'InputValuePlaceholder instead.'
+          .format(input_key, inputs_dict[input_key].type))
     else:
       return "{{{{$.inputs.artifacts['{}'].path}}}}".format(input_key)