Add support for generic unions

RELEASE.md

@@ -0,0 +1,3 @@
+Release type: patch
+
+Attempt to merge union types during schema conversion.

strawberry/schema/schema_converter.py

@@ -856,9 +856,14 @@ def from_union(self, union: StrawberryUnion) -> GraphQLUnionType:
 
  if isinstance(graphql_type, GraphQLInputObjectType):
  raise InvalidTypeInputForUnion(graphql_type)
- assert isinstance(graphql_type, GraphQLObjectType)
+ assert isinstance(graphql_type, (GraphQLObjectType, GraphQLUnionType))
 
- graphql_types.append(graphql_type)
+ # If the graphql_type is a GraphQLUnionType, merge its child types
+ if isinstance(graphql_type, GraphQLUnionType):
+ # Add the child types of the GraphQLUnionType to the list of graphql_types
+ graphql_types.extend(graphql_type.types)
+ else:
+ graphql_types.append(graphql_type)
 
  graphql_union = GraphQLUnionType(
  name=union_name,

tests/schema/test_union.py

@@ -856,3 +856,117 @@
 
  assert not result.errors
  assert result.data["something"] == {"__typename": "A", "a": 5}
+
+
+@pytest.mark.xfail(reason="Not supported yet")
+def test_generic_union_with_annotated():
+ @strawberry.type
+ class SomeType:
+ id: strawberry.ID
+ name: str
+
+ @strawberry.type
+ class NotFoundError:
+ id: strawberry.ID
+ message: str
+
+ T = TypeVar("T")
+
+ @strawberry.type
+ class ObjectQueries(Generic[T]):
+ @strawberry.field
+ def by_id(
+ self, id: strawberry.ID
+ ) -> Annotated[Union[T, NotFoundError], strawberry.union("ByIdResult")]: ...
+
+ @strawberry.type
+ class Query:
+ @strawberry.field
+ def some_type_queries(self, id: strawberry.ID) -> ObjectQueries[SomeType]:
+ raise NotImplementedError()
+
+ schema = strawberry.Schema(Query)
+
+ # TODO: check the name
+ assert (
+ str(schema)
+ == textwrap.dedent(
+ """
+ type NotFoundError {
+ id: ID!
+ message: String!
+ }
+
+ type Query {
+ someTypeQueries(id: ID!): SomeTypeByIdResult!
+ }
+
+ type SomeType {
+ id: ID!
+ name: String!
+ }
+
+ union SomeTypeNotFoundError = SomeType | NotFoundError
+
+ type SomeTypeObjectQueries {
+ byId(id: ID!): SomeTypeByIdResult!
+ }
+ """
+ ).strip()
+ )
+
+
+def test_generic_union_with_annotated_inside():
+ @strawberry.type
+ class SomeType:
+ id: strawberry.ID
+ name: str
+
+ @strawberry.type
+ class NotFoundError:
+ id: strawberry.ID
+ message: str
+
+ T = TypeVar("T")
+
+ @strawberry.type
+ class ObjectQueries(Generic[T]):
+ @strawberry.field
+ def by_id(
+ self, id: strawberry.ID
+ ) -> Union[T, Annotated[NotFoundError, strawberry.union("ByIdResult")]]: ...
+
+ @strawberry.type
+ class Query:
+ @strawberry.field
+ def some_type_queries(self, id: strawberry.ID) -> ObjectQueries[SomeType]:
+ return ObjectQueries(SomeType)
+
+ schema = strawberry.Schema(Query)
+
+ assert (
+ str(schema)
+ == textwrap.dedent(
+ """
+ type NotFoundError {
+ id: ID!
+ message: String!
+ }
+
+ type Query {
+ someTypeQueries(id: ID!): SomeTypeObjectQueries!
+ }
+
+ type SomeType {
+ id: ID!
+ name: String!
+ }
+
+ union SomeTypeByIdResult = SomeType | NotFoundError
+
+ type SomeTypeObjectQueries {
+ byId(id: ID!): SomeTypeByIdResult!
+ }
+ """
+ ).strip()
+ )