[sdk] Error occurs for component_input_parameter in v2 compiler

[TrsNium]

Environment

• KFP SDK version:
  1.6.3

Steps to reproduce

Define and execute a pipeline with the following code

slack_notification_op = comp.load_component_from_text(
    read_file("components/slack-notification/component.yaml")
)

def get_before_days(date: str, fmt: str, days: int) -> str:
    """
    Subtract the number of days from the date from the date and the number of days specified in the argument.

    Parameters
    ----------
    date: str
        Original Date
    fmt: str
        Date formate with a (strftime, strptime) format
    days: int
        The number of days to subtract.
    """
    from datetime import datetime, timedelta

    dt = datetime.strptime(date, fmt)
    new_dt = dt - timedelta(days=days)
    return new_dt.strftime(fmt)

@dsl.pipeline(
    name="test",
    description="",
)
def feature_extract_pipeline(
    vertex_pipelines_project_id: str,
    dataset_id: str,
    pipelines_url: str,
    slack_webhook: str,
    target_date: str,
):
    with dsl.ExitHandler(
        exit_op=slack_notification_op(
            job_name="{{workflow.name}}",
            webhook_url=slack_webhook,
            status="{{workflow.status}}",
            pipelines_url=f"{pipelines_url}/pipeline/#/runs/details/{{{{workflow.uid}}}}",
        )
    ):
        get_before_a_days_op = comp.create_component_from_func(
            func=get_before_days, base_image="python:alpine"
        )
        before_a_day = get_before_a_days_op(
            target_date, "%Y%m%d", 1
        )

from kfp.v2 import compiler
import tempfile
with tempfile.TemporaryDirectory() as tempdir:
    package_path = os.path.join(tempdir, "pipeline.json")
    # NOTE: The type_check argument is probably not working.
    compiler.Compiler().compile(pipeline_func=feature_extract_pipeline, package_path=package_path)

following is error messsage

ata/.pyenv/versions/3.7.1rc1/lib/python3.7/site-packages/kfp/v2/compiler/compiler.py", line 687, in _group_to_dag_spec
    input_artifacts_in_current_dag,
  File "/Users/takuya.hirata/.pyenv/versions/3.7.1rc1/lib/python3.7/site-packages/kfp/dsl/component_spec.py", line 338, in update_task_inputs_spec
    component_input_parameter, parent_component_inputs)
AssertionError: component_input_parameter: pipelineparam--pipelineparam--target_date not found. All inputs:

I got same error occurred when using from kfp.v2.dsl import component.
If you use a python function with component, you will get an error like the one above

Expected result

No errors occur during compilation.

---

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[TrsNium]

I noticed that I can compile without using the exit handler.
I just did a print debugging.
The target_date is recognized as a input_parameter of the subgroup component, but there is no such parameter in the parent, which may be causing the above error.

**********************group.name***************
group.name: exit-handler-1, rootgroup_name: 8a1b7dd5281c40c3aee5c15a24814903
********************root spec******************
input_definitions {
  parameters {
    key: "category_models"
    value {
      type: STRING
    }
  }
  parameters {
    key: "dataset_id"
    value {
      type: STRING
    }
  }
  parameters {
    key: "metric_bucket_url"
    value {
      type: STRING
    }
  }
  parameters {
    key: "metric_image"
    value {
      type: STRING
    }
  }
  parameters {
    key: "output_gcs_path"
    value {
      type: STRING
    }
  }
  parameters {
    key: "parallel_num"
    value {
      type: INT
    }
  }
  parameters {
    key: "pipelines_url"
    value {
      type: STRING
    }
  }
  parameters {
    key: "service_project_id"
    value {
      type: STRING
    }
  }
  parameters {
    key: "slack_webhook"
    value {
      type: STRING
    }
  }
  parameters {
    key: "snap_item_limit"
    value {
      type: STRING
    }
  }
  parameters {
    key: "target_date"
    value {
      type: STRING
    }
  }
  parameters {
    key: "vertex_pipelines_project_id"
    value {
      type: STRING
    }
  }
}
dag {
  tasks {
    key: "exit-handler-1"
    value {
      task_info {
        name: "exit-handler-1"
      }
      component_ref {
        name: "comp-exit-handler-1"
      }
    }
  }
}

********************group component spec******************
{'comp-exit-handler-1': }

********************subgroup params*****************
[{{pipelineparam:op=;name=target_date}}]

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

Lines 615 to 618 in a41a72f

	if group.name == rootgroup_name:
	group_component_spec = pipeline_spec.root
	else:
	group_component_spec = pipeline_spec.components[group_component_name]

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

Line 663 in a41a72f

subgroup_params = [param for param, _ in subgroup_inputs]

exit-handler group does not have parameters, So I figured the error would occur.

[TrsNium]

@chensun hello.
Could you review this PR? #5899