Fix handling of Enums in Literal types

Author: brakhane

src/cattr/converters.py

@@ -405,9 +405,17 @@ def _structure_call(obj, cl):
 
     @staticmethod
     def _structure_literal(val, type):
-        if val not in type.__args__:
-            raise Exception(f"{val} not in literal {type}")
-        return val
+        vals = set(type.__args__)
+        enums = {x for x in vals if isinstance(x, Enum)}
+        literal_vals = vals.difference(enums)
+        if val not in literal_vals:
+            enum_vals = {x.value: x for x in enums}
+            if val not in enum_vals:
+                raise Exception(f"{val} not in literal {type}")
+            else:
+                return enum_vals[val]
+        else:
+            return val
 
     # Attrs classes.
 

tests/test_structure_attrs.py

@@ -1,4 +1,5 @@
 """Loading of attrs classes."""
+from enum import Enum
 from ipaddress import IPv4Address, IPv6Address, ip_address
 from typing import Union
 from unittest.mock import Mock
@@ -164,6 +165,27 @@ class ClassWithLiteral:
     ) == ClassWithLiteral(4)
 
 
+@pytest.mark.skipif(is_py37, reason="Not supported on 3.7")
+@pytest.mark.parametrize("converter_cls", [Converter, GenConverter])
+def test_structure_literal_enum(converter_cls):
+    """Structuring a class with a literal field works."""
+    from typing import Literal
+
+    converter = converter_cls()
+
+    class Foo(Enum):
+        FOO = 1
+        BAR = 2
+
+    @define
+    class ClassWithLiteral:
+        literal_field: Literal[Foo.FOO] = Foo.FOO
+
+    assert converter.structure(
+        {"literal_field": 1}, ClassWithLiteral
+    ) == ClassWithLiteral(Foo.FOO)
+
+
 @pytest.mark.skipif(is_py37, reason="Not supported on 3.7")
 @pytest.mark.parametrize("converter_cls", [Converter, GenConverter])
 def test_structure_literal_multiple(converter_cls):
@@ -172,16 +194,33 @@ def test_structure_literal_multiple(converter_cls):
 
     converter = converter_cls()
 
+    class Foo(Enum):
+        FOO = 1
+        FOOFOO = 2
+
+    class Bar(Enum):
+        BAR = 8
+        BARBAR = 9
+
     @define
     class ClassWithLiteral:
-        literal_field: Literal[4, 5] = 4
+        literal_field: Literal[4, 5, Literal[6], Foo.FOO, Bar.BARBAR] = 4
 
     assert converter.structure(
         {"literal_field": 4}, ClassWithLiteral
     ) == ClassWithLiteral(4)
     assert converter.structure(
         {"literal_field": 5}, ClassWithLiteral
     ) == ClassWithLiteral(5)
+    assert converter.structure(
+        {"literal_field": 6}, ClassWithLiteral
+    ) == ClassWithLiteral(6)
+    assert converter.structure(
+        {"literal_field": 1}, ClassWithLiteral
+    ) == ClassWithLiteral(Foo.FOO)
+    assert converter.structure(
+        {"literal_field": 9}, ClassWithLiteral
+    ) == ClassWithLiteral(Bar.BARBAR)
 
 
 @pytest.mark.skipif(is_py37, reason="Not supported on 3.7")