streamable: Use constructor in dataclass_from_dict

This fixes default value assignments after Chia-Network#10561 but also leads to less perfomance due to `__post_init__` being called which at least gets mitigated by Chia-Network#11730.

Author: xdustinface

chia/util/streamable.py

@@ -132,7 +132,7 @@ def dataclass_from_dict(klass: Type[Any], item: Any) -> Any:
     """
     if type(item) == klass:
         return item
-    obj = object.__new__(klass)
+
     if klass not in CONVERT_FUNCTIONS_FOR_STREAMABLE_CLASS:
         # For non-streamable dataclasses we can't populate the cache on startup, so we do it here for convert
         # functions only.
@@ -144,9 +144,13 @@ def dataclass_from_dict(klass: Type[Any], item: Any) -> Any:
         fields = FIELDS_FOR_STREAMABLE_CLASS[klass]
         convert_funcs = CONVERT_FUNCTIONS_FOR_STREAMABLE_CLASS[klass]
 
-    for field, convert_func in zip(fields, convert_funcs):
-        object.__setattr__(obj, field.name, convert_func(item[field.name]))
-    return obj
+    return klass(
+        **{
+            field.name: convert_func(item[field.name])
+            for field, convert_func in zip(fields, convert_funcs)
+            if field.name in item
+        }
+    )
 
 
 def function_to_convert_one_item(f_type: Type[Any]) -> ConvertFunctionType:

tests/core/util/test_streamable.py

@@ -128,15 +128,15 @@ def test_pure_dataclasses_in_dataclass_from_dict() -> None:
     "test_class, input_dict, error",
     [
         [TestDataclassFromDict1, {"a": "asdf", "b": "2", "c": G1Element()}, ValueError],
-        [TestDataclassFromDict1, {"a": 1, "b": "2"}, KeyError],
+        [TestDataclassFromDict1, {"a": 1, "b": "2"}, TypeError],
         [TestDataclassFromDict1, {"a": 1, "b": "2", "c": "asd"}, ValueError],
         [TestDataclassFromDict1, {"a": 1, "b": "2", "c": "00" * G1Element.SIZE}, ValueError],
         [TestDataclassFromDict1, {"a": [], "b": "2", "c": G1Element()}, TypeError],
         [TestDataclassFromDict1, {"a": {}, "b": "2", "c": G1Element()}, TypeError],
         [TestDataclassFromDict2, {"a": "asdf", "b": 1.2345, "c": 1.2345}, TypeError],
         [TestDataclassFromDict2, {"a": 1.2345, "b": {"a": 1, "b": "2"}, "c": 1.2345}, TypeError],
-        [TestDataclassFromDict2, {"a": {"a": 1, "b": "2", "c": G1Element()}, "b": {"a": 1, "b": "2"}}, KeyError],
-        [TestDataclassFromDict2, {"a": {"a": 1, "b": "2"}, "b": {"a": 1, "b": "2"}, "c": 1.2345}, KeyError],
+        [TestDataclassFromDict2, {"a": {"a": 1, "b": "2", "c": G1Element()}, "b": {"a": 1, "b": "2"}}, TypeError],
+        [TestDataclassFromDict2, {"a": {"a": 1, "b": "2"}, "b": {"a": 1, "b": "2"}, "c": 1.2345}, TypeError],
     ],
 )
 def test_dataclass_from_dict_failures(test_class: Type[Any], input_dict: Dict[str, Any], error: Any) -> None: