Add check that literal values are valid to decode_field

dataclasses_jsonschema/__init__.py

@@ -5,6 +5,7 @@
 from decimal import Decimal
 from ipaddress import IPv4Address, IPv6Address
 from typing import Optional, Type, Union, Any, Dict, Tuple, List, Callable, TypeVar
+from typing_extensions import get_args
 import re
 from datetime import datetime, date
 from dataclasses import fields, is_dataclass, Field, MISSING, dataclass, asdict
@@ -438,7 +439,9 @@ def _decode_field(cls, field: str, field_type: Any, value: Any) -> Any:
             field_type_name = cls._get_field_type_name(field_type)
             # Note: Only literal types composed of primitive values are currently supported
             if type(value) in JSON_ENCODABLE_TYPES and (field_type in JSON_ENCODABLE_TYPES or is_literal(field_type)):
-                if is_literal(field_type):
+                if is_literal(field_type) and value not in get_args(field_type):
+                    raise ValueError('Literal value is not in allowed set of values for type.')
+                elif is_literal(field_type):
                     def decoder(_, __, val): return val
                 else:
                     def decoder(_, ft, val): return ft(val)

tests/test_core.py

@@ -1052,3 +1052,26 @@ class Person(JsonSchemaMixin):
     data = Person(name="Joe", pet=Dog(breed="Pug")).to_dict()
     p = Person.from_dict(data)
     assert p.pet == Dog(breed="Pug")
+
+
+def test_decode_literal():
+    @dataclass
+    class Foo(JsonSchemaMixin):
+        common_field: int
+        name: Literal['Foo'] = 'Foo'
+
+    @dataclass
+    class Bar(JsonSchemaMixin):
+        common_field: int
+        name: Literal['Bar'] = 'Bar'
+        other_field: Optional[int] = None
+
+    @dataclass
+    class Baz(JsonSchemaMixin):
+        my_foo_bar: Union[Bar, Foo]
+
+    decoded = Baz.from_dict(Baz(my_foo_bar=Foo(common_field=1)).to_dict())
+
+    # Even though Bar comes first in the Union for 'my_foor_bar', the literal check on 'name' should
+    # verify that this is a Foo and not assign it to a Bar
+    assert type(decoded.my_foo_bar) == Foo