Validate incoming orphan_types are object types

Author: rmosolgo

lib/graphql/schema.rb

@@ -857,6 +857,17 @@ def extra_types(*new_extra_types)
       def orphan_types(*new_orphan_types)
         if new_orphan_types.any?
           new_orphan_types = new_orphan_types.flatten
+          non_object_types = new_orphan_types.reject { |ot| ot.is_a?(Class) && ot < GraphQL::Schema::Object }
+          if non_object_types.any?
+            raise ArgumentError, <<~ERR
+              Only object type classes should be added as `orphan_types(...)`.
+
+              - Remove these no-op types from `orphan_types`: #{non_object_types.map(&:inspect).join(", ")}
+              - See https://graphql-ruby.org/type_definitions/interfaces.html#orphan-types
+
+              To add other types to your schema, you might want `extra_types`: https://graphql-ruby.org/schema/definition.html#extra-types
+            ERR
+          end
           add_type_and_traverse(new_orphan_types, root: false)
           own_orphan_types.concat(new_orphan_types.flatten)
         end

spec/graphql/schema_spec.rb

@@ -152,6 +152,26 @@ class CustomSubscriptions < GraphQL::Subscriptions::ActionCableSubscriptions
     end
   end
 
+  class ExampleOptionEnum < GraphQL::Schema::Enum
+  end
+  it "rejects non-object types to orphan_types" do
+    object_type = Class.new(GraphQL::Schema::Object)
+    err = assert_raises ArgumentError do
+      Class.new(GraphQL::Schema) do
+        orphan_types(ExampleOptionEnum, object_type)
+      end
+    end
+
+    expected_msg = "Only object type classes should be added as `orphan_types(...)`.
+
+- Remove these no-op types from `orphan_types`: ExampleOptionEnum
+- See https://graphql-ruby.org/type_definitions/interfaces.html#orphan-types
+
+To add other types to your schema, you might want `extra_types`: https://graphql-ruby.org/schema/definition.html#extra-types
+"
+    assert_equal expected_msg, err.message
+  end
+
   describe "merged, inherited caches" do
     METHODS_TO_CACHE = {
       types: 1,

spec/support/dummy/schema.rb

@@ -517,7 +517,7 @@ class Schema < GraphQL::Schema
     mutation DairyAppMutation
     subscription Subscription
     max_depth 5
-    orphan_types Honey, Beverage
+    orphan_types Honey
     trace_with GraphQL::Tracing::CallLegacyTracers
 
     rescue_from(NoSuchDairyError) { |err| raise GraphQL::ExecutionError, err.message  }