fix: use Self return type for Model.__from_data__

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+* Changed `compas_model.models.Model.__from_data__` return type to `Self` so subclasses retain their type when deserialized.
+
 ### Removed
 
 

pyproject.toml

@@ -27,14 +27,15 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
 ]
-dependencies = ["compas", "shapely"]
+dependencies = ["compas", "shapely", "typing_extensions"]
 
 [project.optional-dependencies]
 dev = [
     "build",
     "bump-my-version",
     "compas_invocations2",
     "invoke >=0.14",
+    "pyright",
     "pytest",
     "pytest-dependency",
     "ruff",

src/compas_model/models/model.py

@@ -4,6 +4,8 @@
 from typing import TypeVar
 from typing import Union
 
+from typing_extensions import Self
+
 from compas.datastructures import Datastructure
 from compas.geometry import Point
 from compas.geometry import Transformation
@@ -59,7 +61,7 @@ def __data__(self) -> dict:
         return data
 
     @classmethod
-    def __from_data__(cls, data: dict) -> "Model":
+    def __from_data__(cls, data: dict) -> "Self":
         model = cls()
 
         model._transformation = data["transformation"]

tests/test_model.py

@@ -45,8 +45,79 @@
 #     assert c_model.tree is not None
 #     assert len(c_model.tree.elements) == 3
 
+import subprocess
+from pathlib import Path
+
 from compas_model.models import Model  # noqa: F401
 
 
 def test_import():
     assert True
+
+
+def test_from_data_roundtrip_preserves_subclass_behavior():
+    class MyModel(Model):
+        pass
+
+    model = MyModel()
+    data = model.__data__
+    restored = MyModel.__from_data__(data)
+
+    assert isinstance(restored, MyModel)
+    assert restored.__data__ == data
+
+
+def test_self_return_type_with_pyright(tmp_path: Path):
+    test_file = tmp_path / "typing_case.py"
+    test_file.write_text(
+        """
+from typing import assert_type
+
+from compas_model.models import Model
+
+
+class MyModel(Model):
+    pass
+
+
+obj = MyModel.__from_data__(MyModel().__data__)
+assert_type(obj, MyModel)
+"""
+    )
+
+    result = subprocess.run(
+        ["pyright", str(test_file)],
+        text=True,
+        capture_output=True,
+        cwd=Path(__file__).parents[1],
+    )
+
+    assert result.returncode == 0, result.stdout + result.stderr
+
+
+def test_from_data_with_overridden_subclass():
+    class MyModel(Model):
+        def __init__(self, **kwargs):
+            super().__init__(**kwargs)
+            self._extra = None
+
+        @property
+        def __data__(self):
+            data = super().__data__
+            data["extra"] = self._extra
+            return data
+
+        @classmethod
+        def __from_data__(cls, data):
+            model = super().__from_data__(data)
+            model._extra = data.get("extra")
+            return model
+
+    model = MyModel()
+    model._extra = "hello"
+    data = model.__data__
+
+    restored = MyModel.__from_data__(data)
+
+    assert isinstance(restored, MyModel)
+    assert restored._extra == "hello"