add support for union with metadata #166

marshmallow_dataclass/__init__.py

@@ -578,13 +578,18 @@ def _field_for_generic_type(
             )
         from . import union_field
 
+        union_metadata = {
+            k: v
+            for k, v in metadata.items()
+            if k not in ("allow_none", "dump_default", "load_default", "required")
+        }
         return union_field.Union(
             [
                 (
                     subtyp,
                     field_for_schema(
                         subtyp,
-                        metadata={"required": True},
+                        metadata=union_metadata,
                         base_schema=base_schema,
                         typ_frame=typ_frame,
                     ),

tests/test_field_for_schema.py

@@ -11,6 +11,7 @@
     from typing_extensions import Final, Literal  # type: ignore[assignment]
 
 from marshmallow import fields, Schema, validate
+from marshmallow.warnings import RemovedInMarshmallow4Warning
 
 from marshmallow_dataclass import (
     field_for_schema,
@@ -132,6 +133,56 @@ class Color(Enum):
                 marshmallow_enum.EnumField(enum=Color, required=True),
             )
 
+    def test_union_enum(self):
+        class Fruit(Enum):
+            apple = "Apple"
+            banana = "Banana"
+            tomato = "Tomato"
+
+        with self.assertWarns(RemovedInMarshmallow4Warning):
+            if hasattr(fields, "Enum"):
+                self.assertFieldsEqual(
+                    field_for_schema(Union[Fruit, str], metadata={"by_value": True}),
+                    union_field.Union(
+                        [
+                            (
+                                Fruit,
+                                fields.Enum(enum=Fruit, required=True, by_value=True),
+                            ),
+                            (
+                                str,
+                                fields.String(
+                                    required=True, metadata={"by_value": True}
+                                ),
+                            ),
+                        ],
+                        required=True,
+                        metadata={"by_value": True},
+                    ),
+                )
+            else:
+                import marshmallow_enum
+
+                self.assertFieldsEqual(
+                    field_for_schema(Union[Fruit, str], metadata={"by_value": True}),
+                    marshmallow_enum.EnumField(
+                        [
+                            (
+                                Fruit,
+                                fields.Enum(enum=Fruit, required=True, by_value=True),
+                            ),
+                            (
+                                str,
+                                fields.String(
+                                    required=True, metadata={"by_value": True}
+                                ),
+                            ),
+                        ],
+                        required=True,
+                        metadata={"by_value": True},
+                    ),
+                )
+
     def test_literal(self):
         self.assertFieldsEqual(
             field_for_schema(Literal["a"]),

tests/test_union.py

@@ -1,8 +1,10 @@
 from dataclasses import field
+from enum import Enum
 import sys
 import unittest
 from typing import List, Optional, Union, Dict
 
+from marshmallow.warnings import RemovedInMarshmallow4Warning
 import marshmallow
 
 from marshmallow_dataclass import dataclass
@@ -196,3 +198,22 @@ class PEP604IntOrStr:
 
         data_in = {"value": 42}
         self.assertEqual(schema.dump(schema.load(data_in)), data_in)
+
+    def test_union_enum(self):
+        class Fruit(Enum):
+            apple = "Apple"
+            banana = "Banana"
+            tomato = "Tomato"
+
+        @dataclass
+        class Dclass:
+            value: Union[Fruit, dict] = field(metadata={"by_value": True})
+
+        with self.assertWarns(RemovedInMarshmallow4Warning):
+            schema = Dclass.Schema()
+
+        data_in = {"value": "Apple"}
+        self.assertEqual(schema.dump(schema.load(data_in)), data_in)
+
+        data_in = {"value": {"fruit": "Orange"}}
+        self.assertEqual(schema.dump(schema.load(data_in)), data_in)