Fix double nested dataclass defaults, bump version

dcargs/_parsers.py

@@ -79,14 +79,18 @@ def from_dataclass(
 
             # Add arguments for nested dataclasses.
             if _resolver.is_dataclass(field.type):
+                default = None
+                if default_instance is not None:
+                    default = getattr(default_instance, field.name)
+                elif field.default is not dataclasses.MISSING:
+                    default = field.default
+
                 child_definition, child_metadata = ParserDefinition.from_dataclass(
                     field.type,
                     parent_dataclasses | {cls},
                     subparser_name_from_type=subparser_name_from_type,
                     parent_type_from_typevar=type_from_typevar,
-                    default_instance=field.default
-                    if field.default is not dataclasses.MISSING
-                    else None,
+                    default_instance=default,
                 )
                 metadata.update(child_metadata)
 

setup.py

@@ -5,7 +5,7 @@
 
 setup(
     name="dcargs",
-    version="0.0.4",
+    version="0.0.5",
     description="Portable, reusable, strongly typed CLIs from dataclass definitions",
     long_description=long_description,
     long_description_content_type="text/markdown",

tests/test_nested.py

@@ -54,6 +54,28 @@ class Nested:
     assert dcargs.parse(Nested, args=["--x", "1"]) == Nested(x=1, b=B(y=5))
 
 
+def test_double_default_nested():
+    @dataclasses.dataclass
+    class Child:
+        y: int
+
+    @dataclasses.dataclass
+    class Parent:
+        c: Child
+
+    @dataclasses.dataclass
+    class Grandparent:
+        x: int
+        b: Parent = Parent(Child(y=5))
+
+    assert dcargs.parse(Grandparent, args=["--x", "1", "--b.c.y", "3"]) == Grandparent(
+        x=1, b=Parent(Child(y=3))
+    )
+    assert dcargs.parse(Grandparent, args=["--x", "1"]) == Grandparent(
+        x=1, b=Parent(Child(y=5))
+    )
+
+
 # TODO: implement this!
 # def test_optional_nested():
 #     @dataclasses.dataclass