Support Literal and Union/Optional types on structs. Fixes #405

csp/impl/struct.py

@@ -34,7 +34,7 @@ def __new__(cls, name, bases, dct):
                 # Lists need to be normalized too as potentially we need to add a boolean flag to use FastList
                 if v == FastList:
                     raise TypeError(f"{v} annotation is not supported without args")
-                if CspTypingUtils.is_generic_container(v):
+                if CspTypingUtils.is_generic_container(v) or CspTypingUtils.is_union_type(v):
                     actual_type = ContainerTypeNormalizer.normalized_type_to_actual_python_type(v)
                     if CspTypingUtils.is_generic_container(actual_type):
                         raise TypeError(f"{v} annotation is not supported as a struct field [{actual_type}]")

csp/impl/types/container_type_normalizer.py

@@ -73,12 +73,28 @@ def _convert_containers_to_typing_generic_meta(cls, typ, is_within_container):
     def normalized_type_to_actual_python_type(cls, typ, level=0):
         if isinstance(typ, typing_extensions._AnnotatedAlias):
             typ = CspTypingUtils.get_origin(typ)
+
         if CspTypingUtils.is_generic_container(typ):
-            if CspTypingUtils.get_origin(typ) is FastList and level == 0:
+            origin = CspTypingUtils.get_origin(typ)
+            if origin is FastList and level == 0:
                 return [cls.normalized_type_to_actual_python_type(typ.__args__[0], level + 1), True]
-            if CspTypingUtils.get_origin(typ) is typing.List and level == 0:
+            if origin is typing.List and level == 0:
                 return [cls.normalized_type_to_actual_python_type(typ.__args__[0], level + 1)]
+            if origin in (typing.Literal, typing_extensions.Literal):  # Not the same in python 3.8/3.9
+                # Import here to prevent circular import
+                from csp.impl.types.instantiation_type_resolver import UpcastRegistry
+
+                args = typing.get_args(typ)
+                typ = type(args[0])
+                for arg in args[1:]:
+                    typ = UpcastRegistry.instance().resolve_type(typ, type(arg), raise_on_error=False)
+                if typ:
+                    return typ
+                else:
+                    return object
             return cls._NORMALIZED_TYPE_MAPPING.get(CspTypingUtils.get_origin(typ), typ)
+        elif CspTypingUtils.is_union_type(typ):
+            return object
         else:
             return typ
 

csp/tests/impl/test_struct.py

@@ -6,7 +6,7 @@
 import typing
 import unittest
 from datetime import date, datetime, time, timedelta
-from typing import Dict, List, Set, Tuple
+from typing import Dict, List, Literal, Optional, Set, Tuple, Union
 from typing_extensions import Annotated
 
 import csp
@@ -2960,6 +2960,41 @@ class StructWithAnnotations(csp.Struct):
         )
         self.assertEqual(StructWithAnnotations.metadata(typed=False), {"b": float, "d": dict, "s": str})
 
+    def test_literal(self):
+        simple_class0 = SimpleClass(0)
+        simple_class1 = SimpleClass(1)
+
+        class StructWithLiteral(csp.Struct):
+            s: Literal["foo", "bar"]
+            f: Literal[0, 1.0]
+            o: Literal["foo", 0]
+            c: Literal[simple_class0, simple_class1]
+
+        self.assertEqual(
+            StructWithLiteral.metadata(typed=True),
+            {
+                "s": Literal["foo", "bar"],
+                "f": Literal[0, 1.0],
+                "o": Literal["foo", 0],
+                "c": Literal[simple_class0, simple_class1],
+            },
+        )
+        self.assertEqual(StructWithLiteral.metadata(typed=False), {"s": str, "f": float, "o": object, "c": SimpleClass})
+
+    def test_union(self):
+        class StructWithUnion(csp.Struct):
+            o1: Union[int, float]
+            o2: Optional[str]
+
+        self.assertEqual(
+            StructWithUnion.metadata(typed=True),
+            {
+                "o1": Union[int, float],
+                "o2": Optional[str],
+            },
+        )
+        self.assertEqual(StructWithUnion.metadata(typed=False), {"o1": object, "o2": object})
+
 
 if __name__ == "__main__":
     unittest.main()