Add new class instead of dict

server/books/schema/nodes/topic.py

@@ -6,6 +6,10 @@ from graphene_django.filter import DjangoFilterConnectionField
 from books.models import Topic, Module
 from books.schema.nodes import ModuleNode
 
+class NotFoundFailure:
+    reason = 'Not Found'
+
+
 NOT_FOUND = { 'reason': 'Not Found'}
 
 class NotFound(graphene.ObjectType):

server/books/schema/queries.py

@@ -5,7 +5,8 @@ from graphene_django.filter import DjangoFilterConnectionField
 from api.utils import get_object
 from core.logger import get_logger
 from .connections import TopicConnection, ModuleConnection
-from .nodes import ContentBlockNode, ChapterNode, ModuleNode, NOT_FOUND, TopicNode, SnapshotNode, TopicOr404Node
+from .nodes import ContentBlockNode, ChapterNode, ModuleNode, NOT_FOUND, NotFoundFailure, TopicNode, SnapshotNode, \
+    TopicOr404Node
 from ..models import Book, Topic, Module, Chapter, Snapshot
 
 logger = get_logger(__name__)
@@ -66,5 +67,5 @@ class BookQuery(object):
             try:
                 return Topic.objects.get(slug=slug)
             except Topic.DoesNotExist:
-                return NOT_FOUND
+                return NotFoundFailure
         return None

server/schema.graphql

@@ -702,6 +702,10 @@ interface Node {
   id: ID!
 }
 
+type NotFound {
+  reason: String
+}
+
 type NoteNode implements Node {
   id: ID!
   text: String!
@@ -852,7 +856,7 @@ type Query {
   assignment(id: ID!): AssignmentNode
   assignments: [AssignmentNode]
   node(id: ID!): Node
-  topic(slug: String): TopicNode
+  topic(slug: String): TopicOr404Node
   module(slug: String, id: ID): ModuleNode
   chapter(id: ID!): ChapterNode
   contentBlock(id: ID!): ContentBlockNode
@@ -1127,6 +1131,8 @@ type TopicNode implements Node {
   modules(offset: Int, before: String, after: String, first: Int, last: Int, slug: String, slug_Icontains: String, slug_In: [String], title: String, title_Icontains: String, title_In: [String]): ModuleNodeConnection
 }
 
+union TopicOr404Node = TopicNode | NotFound
+
 scalar UUID
 
 input UpdateAnswerArgument {