Return calling class from Asset constructors

Author: duckontheweb

pystac/asset.py

@@ -127,7 +127,8 @@ def clone(self) -> "Asset":
         Returns:
             Asset: The clone of this asset.
         """
-        return Asset(
+        cls = self.__class__
+        return cls(
             href=self.href,
             title=self.title,
             description=self.description,
@@ -139,8 +140,8 @@ def clone(self) -> "Asset":
     def __repr__(self) -> str:
         return "<Asset href={}>".format(self.href)
 
-    @staticmethod
-    def from_dict(d: Dict[str, Any]) -> "Asset":
+    @classmethod
+    def from_dict(cls, d: Dict[str, Any]) -> "Asset":
         """Constructs an Asset from a dict.
 
         Returns:
@@ -156,7 +157,7 @@ def from_dict(d: Dict[str, Any]) -> "Asset":
         if any(d):
             properties = d
 
-        return Asset(
+        return cls(
             href=href,
             media_type=media_type,
             title=title,

tests/test_item.py

@@ -742,3 +742,26 @@ def test_from_file_returns_subclass(self) -> None:
         custom_item = self.BasicCustomItem.from_file(self.SAMPLE_ITEM)
 
         self.assertIsInstance(custom_item, self.BasicCustomItem)
+
+
+class AssetSubClassTest(unittest.TestCase):
+    class CustomAsset(Asset):
+        pass
+
+    def setUp(self) -> None:
+        self.maxDiff = None
+        with open(TestCases.get_path("data-files/item/sample-item.json")) as src:
+            item_dict = json.load(src)
+
+        self.asset_dict = item_dict["assets"]["analytic"]
+
+    def test_from_dict(self) -> None:
+        asset = self.CustomAsset.from_dict(self.asset_dict)
+
+        self.assertIsInstance(asset, self.CustomAsset)
+
+    def test_clone(self) -> None:
+        asset = self.CustomAsset.from_dict(self.asset_dict)
+        cloned_asset = asset.clone()
+
+        self.assertIsInstance(cloned_asset, self.CustomAsset)