🐛 Fix MetaBase.from_dict with Optional

lib/catalog/owid/catalog/utils.py

@@ -305,11 +305,21 @@ def dataclass_from_dict(cls: Optional[Type[T]], d: Dict[str, Any]) -> T:
         if type(None) in args:
             filtered_args = tuple(a for a in args if a is not type(None))
             if len(filtered_args) == 1:
+                # Save the original field_type for Optional[List[...]] case
                 field_type = filtered_args[0]
+                # For Optional[List[...]] case, update the origin and args
+                if get_origin(field_type) is list:
+                    origin = list
+                    args = get_args(field_type)
 
         if origin is list:
-            item_type = args[0]
-            init_args[field_name] = [dataclass_from_dict(item_type, item) for item in v]
+            # Check if we have type arguments (e.g. List[str])
+            if args:
+                item_type = args[0]
+                init_args[field_name] = [dataclass_from_dict(item_type, item) for item in v]
+            else:
+                # No type arguments, just use the values as-is
+                init_args[field_name] = v
         elif origin is dict:
             key_type, value_type = args
             init_args[field_name] = {k: dataclass_from_dict(value_type, item) for k, item in v.items()}

lib/catalog/tests/test_meta.py

@@ -3,7 +3,7 @@
 #
 
 from dataclasses import dataclass
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional
 
 import pytest
 import yaml
@@ -121,3 +121,17 @@ def test_hash():
     var_c = meta.VariableMeta(display={"d": {"a": 1, "b": 2, "c": 3}})
     assert var_a == var_b
     assert var_a != var_c
+
+
+def test_from_dict():
+    @dataclass
+    class X(meta.MetaBase):
+        a: int
+
+    @dataclass
+    class Y(meta.MetaBase):
+        x_list: Optional[List[X]] = None
+
+    # list of objects should be correctly loaded as that object
+    y = Y.from_dict({"x_list": [{"a": 1}]})
+    assert isinstance(y.x_list[0], X)