feat: add serializable parameter

gokart/__init__.py

@@ -1,7 +1,7 @@
 from gokart.build import WorkerSchedulerFactory, build  # noqa:F401
 from gokart.info import make_tree_info, tree_info  # noqa:F401
 from gokart.pandas_type_config import PandasTypeConfig  # noqa:F401
-from gokart.parameter import ExplicitBoolParameter, ListTaskInstanceParameter, TaskInstanceParameter  # noqa:F401
+from gokart.parameter import ExplicitBoolParameter, ListTaskInstanceParameter, SerializableParameter, TaskInstanceParameter  # noqa:F401
 from gokart.run import run  # noqa:F401
 from gokart.task import TaskOnKart  # noqa:F401
 from gokart.testing import test_run  # noqa:F401

gokart/parameter.py

@@ -1,6 +1,7 @@
 import bz2
 import json
 from logging import getLogger
+from typing import Generic, Protocol, TypeVar
 
 import luigi
 from luigi import task_register
@@ -87,3 +88,34 @@ def __init__(self, *args, **kwargs):
 
     def _parser_kwargs(self, *args, **kwargs):  # type: ignore
         return luigi.Parameter._parser_kwargs(*args, *kwargs)
+
+
+T = TypeVar('T')
+
+
+class Serializable(Protocol):
+    def gokart_serialize(self) -> str:
+        """Implement this method to serialize the object as an parameter
+        You can omit some fields from results of serialization if you want to ignore changes of them
+        """
+        ...
+
+    @classmethod
+    def gokart_deserialize(cls: type[T], s: str) -> T:
+        """Implement this method to deserialize the object from a string"""
+        ...
+
+
+S = TypeVar('S', bound=Serializable)
+
+
+class SerializableParameter(luigi.Parameter, Generic[S]):
+    def __init__(self, object_type: type[S], *args, **kwargs):
+        self._object_type = object_type
+        super().__init__(*args, **kwargs)
+
+    def parse(self, s: str) -> S:
+        return self._object_type.gokart_deserialize(s)
+
+    def serialize(self, x: S) -> str:
+        return x.gokart_serialize()

test/test_serializable_parameter.py

@@ -0,0 +1,83 @@
+import json
+import tempfile
+from dataclasses import asdict, dataclass
+
+import luigi
+import pytest
+from luigi.cmdline_parser import CmdlineParser
+from mypy import api
+
+from gokart import SerializableParameter, TaskOnKart
+from test.config import PYPROJECT_TOML
+
+
+@dataclass(frozen=True)
+class Config:
+    foo: int
+    bar: str
+
+    def gokart_serialize(self) -> str:
+        # dict is ordered in Python 3.7+
+        return json.dumps(asdict(self))
+
+    @classmethod
+    def gokart_deserialize(cls, s: str) -> 'Config':
+        return cls(**json.loads(s))
+
+
+class SerializableParameterWithOutDefault(TaskOnKart):
+    task_namespace = __name__
+    config: Config = SerializableParameter(object_type=Config)
+
+    def run(self):
+        self.dump(self.config)
+
+
+class SerializableParameterWithDefault(TaskOnKart):
+    task_namespace = __name__
+    config: Config = SerializableParameter(object_type=Config, default=Config(foo=1, bar='bar'))
+
+    def run(self):
+        self.dump(self.config)
+
+
+class TestSerializableParameter:
+    def test_default(self):
+        with CmdlineParser.global_instance([f'{__name__}.SerializableParameterWithDefault']) as cp:
+            assert cp.get_task_obj().config == Config(foo=1, bar='bar')
+
+    def test_parse_param(self):
+        with CmdlineParser.global_instance([f'{__name__}.SerializableParameterWithOutDefault', '--config', '{"foo": 100, "bar": "val"}']) as cp:
+            assert cp.get_task_obj().config == Config(foo=100, bar='val')
+
+    def test_missing_parameter(self):
+        with pytest.raises(luigi.parameter.MissingParameterException):
+            with CmdlineParser.global_instance([f'{__name__}.SerializableParameterWithOutDefault']) as cp:
+                cp.get_task_obj()
+
+    def test_value_error(self):
+        with pytest.raises(ValueError):
+            with CmdlineParser.global_instance([f'{__name__}.SerializableParameterWithOutDefault', '--config', 'Foo']) as cp:
+                cp.get_task_obj()
+
+    def test_expected_one_argument_error(self):
+        with pytest.raises(SystemExit):
+            with CmdlineParser.global_instance([f'{__name__}.SerializableParameterWithOutDefault', '--config']) as cp:
+                cp.get_task_obj()
+
+    def test_mypy(self):
+        """check invalid object cannot used for SerializableParameter"""
+
+        test_code = """
+import gokart
+
+class InvalidClass:
+    ...
+
+gokart.SerializableParameter(object_type=InvalidClass)
+        """
+        with tempfile.NamedTemporaryFile(suffix='.py') as test_file:
+            test_file.write(test_code.encode('utf-8'))
+            test_file.flush()
+            result = api.run(['--no-incremental', '--cache-dir=/dev/null', '--config-file', str(PYPROJECT_TOML), test_file.name])
+            assert 'Value of type variable "S" of "SerializableParameter" cannot be "InvalidClass"  [type-var]' in result[0]