fix default for a nested config

Author: vassilyl

msrc-appconfig-dataclasses/tests/decl_dataclasses_test.py

@@ -86,3 +86,18 @@ def test_unsupported():
         Schema(DictsNotSupported)
     with pytest.raises(ValueError):
         Schema(NonUniformTuplesNotSupported)
+
+
+@dataclass(frozen=True)
+class Inner():
+    b: int
+
+
+@dataclass(frozen=True)
+class Outer():
+    a2: Inner = Inner(2)
+
+
+def test_dataclass_gather_nested_default():
+    c = msrc.appconfig.gather_config(Outer, argv=[])
+    assert c.a2.b == 2

msrc-appconfig/msrc/appconfig/schema.py

@@ -174,10 +174,20 @@ def __init__(
         self.element_type: ElementType = element_type
         self.is_secret: bool = is_secret
         self.has_default: bool = has_default
-        self.default_value = default_value
         if has_default and not self.type_check(default_value):
             raise ValueError("Element default value %r must have type %r."
                              % (default_value, element_type))
+        if isinstance(element_type, Schema) and has_default:
+            # substitute schema elements taking defaults from the default value
+            for name in element_type.keys():
+                i = element_type[name]
+                element_type[name] = Element(
+                    i.element_type,
+                    True,
+                    getattr(default_value, name),
+                    i.help,
+                    i.is_secret)
+        self.default_value = default_value
 
     def type_check(self, value: object) -> bool:
         """Checks type of the value against element type."""
@@ -349,6 +359,8 @@ def args_generator() -> Iterable[Tuple[str, object]]:
                         if not isinstance(v, Mapping):
                             raise ValueError(
                                 f"invalid value {v!r} for {n!r}")
+                        if el.has_default:
+                            v = dict(elt.to_dict(el.default_value, True), **v)
                         yield n, elt.from_dict(v)
                     else:
                         yield n, el.parse(v)

msrc-appconfig/tests/schema_test.py

@@ -170,7 +170,22 @@ def test_to_dict():
     schema = s.Schema(CheckDefaults)
     data = dict(f1=34, f6=(12, 13), f8=dict(booleans=(False, True)))
     instance = schema.from_dict(data)
-    assert data == schema.to_dict(instance)
+    result = schema.to_dict(instance)
+    assert result == data
+    result = schema.to_dict(instance, include_defaults=True)
+    assert result == dict(
+        f0="string",
+        f1=34,
+        f2=3.14,
+        f3=True,
+        f4=En.Option2,
+        f5=("a", "b"),
+        f6=(12, 13),
+        f7=(1, 2, 3),
+        f8=dict(
+            booleans=(False, True),
+            options=(En.Option2, En.Option1))
+    )
 
 
 def test_to_dict_error():