Proposed fix for lovasoa#161 (lovasoa#162)

* Fix for lovasoa#161

* Update CHANGELOG.md

* v8.5.3

Author: dairiki

CHANGELOG.md

@@ -1,5 +1,10 @@
 # marshmallow\_dataclass change log
 
+## v8.5.3
+
+- Fix spurious `ValueError` when defining a Union field with explicit default value
+  ([#161](https://github.com/lovasoa/marshmallow_dataclass/pull/161))
+
 ## v8.5.2
 
 - Fix spurious `TypeError` when serializing `Optional` union types with `required=True`

marshmallow_dataclass/__init__.py

@@ -506,7 +506,7 @@ def _field_for_generic_type(
                     (
                         subtyp,
                         field_for_schema(
-                            subtyp, metadata=metadata, base_schema=base_schema
+                            subtyp, metadata={"required": True}, base_schema=base_schema
                         ),
                     )
                     for subtyp in subtypes

setup.py

@@ -1,6 +1,6 @@
 from setuptools import setup, find_packages
 
-VERSION = "8.5.2"
+VERSION = "8.5.3"
 
 CLASSIFIERS = [
     "Development Status :: 4 - Beta",

tests/test_field_for_schema.py

@@ -139,24 +139,8 @@ def test_union_multiple_types_with_none(self):
             field_for_schema(Union[int, str, None]),
             union_field.Union(
                 [
-                    (
-                        int,
-                        fields.Integer(
-                            allow_none=True,
-                            required=False,
-                            dump_default=None,
-                            load_default=None,
-                        ),
-                    ),
-                    (
-                        str,
-                        fields.String(
-                            allow_none=True,
-                            required=False,
-                            dump_default=None,
-                            load_default=None,
-                        ),
-                    ),
+                    (int, fields.Integer(required=True)),
+                    (str, fields.String(required=True)),
                 ],
                 required=False,
                 dump_default=None,
@@ -169,24 +153,8 @@ def test_optional_multiple_types(self):
             field_for_schema(Optional[Union[int, str]]),
             union_field.Union(
                 [
-                    (
-                        int,
-                        fields.Integer(
-                            allow_none=True,
-                            required=False,
-                            dump_default=None,
-                            load_default=None,
-                        ),
-                    ),
-                    (
-                        str,
-                        fields.String(
-                            allow_none=True,
-                            required=False,
-                            dump_default=None,
-                            load_default=None,
-                        ),
-                    ),
+                    (int, fields.Integer(required=True)),
+                    (str, fields.String(required=True)),
                 ],
                 required=False,
                 dump_default=None,

tests/test_union.py

@@ -166,3 +166,17 @@ class Dclass:
         for value in None, 42, "strvar":
             self.assertEqual(schema.dump(Dclass(value=value)), {"value": value})
             self.assertEqual(schema.load({"value": value}), Dclass(value=value))
+
+    def test_union_with_default(self):
+        @dataclass
+        class IntOrStrWithDefault:
+            value: Union[int, str] = 42
+
+        schema = IntOrStrWithDefault.Schema()
+        self.assertEqual(schema.load({}), IntOrStrWithDefault(value=42))
+        for value in 13, "strval":
+            self.assertEqual(
+                schema.load({"value": value}), IntOrStrWithDefault(value=value)
+            )
+        with self.assertRaises(marshmallow.exceptions.ValidationError):
+            schema.load({"value": None})