Handle UNSET values in the strawberry schema.

The codegen currently chokes on `strawberry.UNSET` default values.  This PR updates the codegen to stop raising an exception and instead pass a `GraphQLNullValue(value=UNSET)` to the plugins.  The default python plugin writes a `None` as the default value because there really isn't a well understood concept of UNSET in the python eco
system.  User defined plugins have all the information that they need to handle this differently if they choose to do so.

strawberry/codegen/plugins/python.py

@@ -10,6 +10,7 @@
     GraphQLEnum,
     GraphQLEnumValue,
     GraphQLList,
+    GraphQLNullValue,
     GraphQLObjectType,
     GraphQLOptional,
     GraphQLScalar,
@@ -141,6 +142,8 @@ def _print_argument_value(self, argval: GraphQLArgumentValue) -> str:
                     "GraphQLEnumValue must have a type for python code gen. {argval}"
                 )
             return f"{argval.enum_type}.{argval.name}"
+        if isinstance(argval, GraphQLNullValue):
+            return "None"
         if not hasattr(argval, "value"):
             raise TypeError(f"Unrecognized values type: {argval}")
         return repr(argval.value)

strawberry/codegen/query_codegen.py

@@ -52,6 +52,7 @@
 )
 from strawberry.types.types import StrawberryObjectDefinition
 from strawberry.union import StrawberryUnion
+from strawberry.unset import UNSET
 from strawberry.utils.str_converters import capitalize_first, to_camel_case
 
 from .exceptions import (
@@ -178,8 +179,9 @@ def _get_deps(t: GraphQLType) -> Iterable[GraphQLType]:
 
 def _py_to_graphql_value(obj: Any) -> GraphQLArgumentValue:
     """Convert a python object to a GraphQLArgumentValue."""
-    if obj is None:
-        return GraphQLNullValue()
+    if obj is None or obj is UNSET:
+        return GraphQLNullValue(value=obj)
+
     obj_type = type(obj)
     if obj_type in _TYPE_TO_GRAPHQL_TYPE:
         return _TYPE_TO_GRAPHQL_TYPE[obj_type](obj)

strawberry/codegen/types.py

@@ -6,6 +6,7 @@
 if TYPE_CHECKING:
     from enum import EnumMeta
     from typing_extensions import Literal
+    from strawberry.unset import UnsetType
 
 
 @dataclass
@@ -134,7 +135,7 @@ class GraphQLBoolValue:
 class GraphQLNullValue:
     """A class that represents a GraphQLNull value."""
 
-    value: None = None
+    value: None | UnsetType = None
 
 
 @dataclass

tests/codegen/conftest.py

@@ -60,6 +60,7 @@ class Image(Node):
 @strawberry.input
 class PersonInput:
     name: str
+    age: Optional[int] = strawberry.UNSET
 
 
 @strawberry.input

tests/codegen/snapshots/python/variables.py

@@ -5,6 +5,7 @@ class OperationNameResult:
 
 class PersonInput:
     name: str
+    age: Optional[int] = None
 
 class ExampleInput:
     id: str

tests/codegen/snapshots/typescript/variables.ts

@@ -4,6 +4,7 @@ type OperationNameResult = {
 
 type PersonInput = {
     name: string
+    age: number | undefined
 }
 
 type ExampleInput = {