feat(sdk): expose IfPresentPlaceholder and ConcatPlaceholder to kfp.dsl

sdk/python/kfp/compiler/test_data/components/container_with_concat_placeholder.py

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from kfp.components import placeholders
+from kfp.dsl import ConcatPlaceholder
 from kfp.dsl import container_component
 from kfp.dsl import ContainerSpec
 from kfp.dsl import Dataset
@@ -26,7 +26,7 @@ def container_with_concat_placeholder(text1: str, text2: Output[Dataset],
         image='python:3.7',
         command=[
             'my_program',
-            placeholders.ConcatPlaceholder(['prefix-', text1, text2.uri])
+            ConcatPlaceholder(['prefix-', text1, text2.uri])
         ],
         args=['--output_path', output_path])
 

sdk/python/kfp/compiler/test_data/components/container_with_if_placeholder.py

@@ -11,12 +11,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from typing import Optional
-
-from kfp.components import placeholders
 from kfp.dsl import container_component
 from kfp.dsl import ContainerSpec
 from kfp.dsl import Dataset
+from kfp.dsl import IfPresentPlaceholder
 from kfp.dsl import Output
 from kfp.dsl import OutputPath
 
@@ -29,11 +27,11 @@ def container_with_if_placeholder(output_path: OutputPath(str),
         image='python:3.7',
         command=[
             'my_program',
-            placeholders.IfPresentPlaceholder(
+            IfPresentPlaceholder(
                 input_name='optional_input',
                 then=[optional_input],
                 else_=['bye']), '--dataset',
-            placeholders.IfPresentPlaceholder(
+            IfPresentPlaceholder(
                 input_name='optional_input', then=[dataset.uri], else_=['bye'])
         ],
         args=['--output_path', output_path])

sdk/python/kfp/components/placeholders.py

@@ -259,10 +259,23 @@ class ConcatPlaceholder(base_model.BaseModel, Placeholder):
     """Placeholder for concatenating multiple strings. May contain other
     placeholders.
 
-    Attributes:
-        items: Elements to concatenate.
+    Examples:
+      ::
+
+        @container_component
+        def container_with_concat_placeholder(text1: str, text2: Output[Dataset],
+                                              output_path: OutputPath(str)):
+            return ContainerSpec(
+                image='python:3.7',
+                command=[
+                    'my_program',
+                    ConcatPlaceholder(['prefix-', text1, text2.uri])
+                ],
+                args=['--output_path', output_path]
+            )
     """
     items: List[CommandLineElement]
+    """Elements to concatenate."""
 
     @classmethod
     def split_cel_concat_string(self, string: str) -> List[str]:
@@ -338,18 +351,36 @@ class IfPresentPlaceholder(base_model.BaseModel, Placeholder):
     """Placeholder for handling cases where an input may or may not be passed.
     May contain other placeholders.
 
-    Attributes:
-        input_name: name of the input/output.
-        then: If the input/output specified in name is present
-            the command-line argument will be replaced at run-time by the
-            expanded value of then.
-        else_: If the input/output specified in name is not present,
-            the command-line argument will be replaced at run-time by the
-            expanded value of otherwise.
+    Examples:
+      ::
+
+        @container_component
+        def container_with_if_placeholder(output_path: OutputPath(str),
+                                          dataset: Output[Dataset],
+                                          optional_input: str = 'default'):
+            return ContainerSpec(
+                    image='python:3.7',
+                    command=[
+                        'my_program',
+                        IfPresentPlaceholder(
+                            input_name='optional_input',
+                            then=[optional_input],
+                            else_=['no_input']), '--dataset',
+                        IfPresentPlaceholder(
+                            input_name='optional_input', then=[dataset.uri], else_=['no_dataset'])
+                    ],
+                    args=['--output_path', output_path]
+                )
     """
     input_name: str
+    """name of the input/output."""
+
     then: List[CommandLineElement]
+    """If the input/output specified in name is present, the command-line argument will be replaced at run-time by the expanded value of then."""
+
     else_: Optional[List[CommandLineElement]] = None
+    """If the input/output specified in name is not present, the command-line argument will be replaced at run-time by the expanded value of otherwise."""
+
     _aliases = {'input_name': 'inputName', 'else_': 'else'}
 
     @classmethod

sdk/python/kfp/components/structures_test.py

@@ -512,7 +512,7 @@ def comp_with_artifact_output(dataset_old: dsl.Output[dsl.Dataset],
                 image='gcr.io/my-image',
                 command=['sh', 'run.sh'],
                 args=[
-                    placeholders.IfPresentPlaceholder(
+                    dsl.IfPresentPlaceholder(
                         input_name='optional_input',
                         then=[dataset_old],
                         else_=[dataset_new])

sdk/python/kfp/dsl/__init__.py

@@ -42,13 +42,17 @@
     'PIPELINE_JOB_ID_PLACEHOLDER',
     'PIPELINE_TASK_NAME_PLACEHOLDER',
     'PIPELINE_TASK_ID_PLACEHOLDER',
+    'IfPresentPlaceholder',
+    'ConcatPlaceholder',
 ]
 
 from kfp.components.component_decorator import component
 from kfp.components.container_component_decorator import container_component
 from kfp.components.importer_node import importer
 from kfp.components.pipeline_context import pipeline
 from kfp.components.pipeline_task import PipelineTask
+from kfp.components.placeholders import ConcatPlaceholder
+from kfp.components.placeholders import IfPresentPlaceholder
 from kfp.components.structures import ContainerSpec
 from kfp.components.task_final_status import PipelineTaskFinalStatus
 from kfp.components.tasks_group import Condition