fix(mapSchema): mapping fields to new types

packages/utils/src/rewire.ts

@@ -41,10 +41,14 @@ export function rewireTypes(
   typeMap: TypeMap;
   directives: Array<GraphQLDirective>;
 } {
+  const referenceTypeMap = Object.create(null);
+  Object.keys(originalTypeMap).forEach(typeName => {
+    referenceTypeMap[typeName] = originalTypeMap[typeName];
+  });
   const newTypeMap: TypeMap = Object.create(null);
 
-  Object.keys(originalTypeMap).forEach(typeName => {
-    const namedType = originalTypeMap[typeName];
+  Object.keys(referenceTypeMap).forEach(typeName => {
+    const namedType = referenceTypeMap[typeName];
 
     if (namedType == null || typeName.startsWith('__')) {
       return;
@@ -194,10 +198,10 @@ export function rewireTypes(
       const rewiredType = rewireType(type.ofType);
       return rewiredType != null ? (new GraphQLNonNull(rewiredType) as T) : null;
     } else if (isNamedType(type)) {
-      let rewiredType = originalTypeMap[type.name];
+      let rewiredType = referenceTypeMap[type.name];
       if (rewiredType === undefined) {
-        rewiredType = isNamedStub(type) ? getBuiltInForStub(type) : type;
-        newTypeMap[rewiredType.name] = rewiredType;
+        rewiredType = isNamedStub(type) ? getBuiltInForStub(type) : rewireNamedType(type);
+        newTypeMap[rewiredType.name] = referenceTypeMap[type.name] = rewiredType;
       }
       return rewiredType != null ? (newTypeMap[rewiredType.name] as T) : null;
     }

packages/utils/tests/schemaTransforms.test.ts

@@ -20,6 +20,8 @@ import {
   GraphQLEnumType,
   GraphQLInt,
   GraphQLList,
+  getNamedType,
+  GraphQLNonNull,
 } from 'graphql';
 
 import formatDate from 'dateformat';
@@ -33,6 +35,8 @@ import {
   ExecutionResult,
 } from '@graphql-tools/utils';
 
+import { addMocksToSchema } from '@graphql-tools/mock';
+
 const typeDefs = `
   directive @schemaDirective(role: String) on SCHEMA
   directive @schemaExtensionDirective(role: String) on SCHEMA
@@ -1129,4 +1133,108 @@ describe('@directives', () => {
       });
     });
   });
+
+  test('allows creation of types that reference other types (issue #1877)', async () => {
+    function listWrapperTransformer(schema: GraphQLSchema) {
+      const listWrapperTypes = new Map();
+      return mapSchema(schema, {
+        [MapperKind.COMPOSITE_FIELD]: (fieldConfig, fieldName) => {
+          const hasDirectiveAnnotation = !!getDirectives(schema, fieldConfig)['addListWrapper'];
+
+          // Leave the field untouched if it does not have the directive annotation
+          if (!hasDirectiveAnnotation) {
+            return undefined;
+          }
+
+          const itemTypeInList = getNamedType(fieldConfig.type);
+          const itemTypeNameInList = itemTypeInList.name;
+
+          // 1. Creating the XListWrapper type and replace the type of the field with that
+          if (!listWrapperTypes.has(itemTypeNameInList)) {
+            listWrapperTypes.set(itemTypeNameInList, new GraphQLObjectType({
+              name: `${itemTypeNameInList}ListWrapper`,
+              fields: {
+                // Adding `size` field
+                size: {
+                  type: new GraphQLNonNull(GraphQLInt),
+                  description: 'The number of items in the `items` field',
+                },
+                // Creating a new List which contains the same type than the original List
+                items: {
+                  type: new GraphQLNonNull(new GraphQLList(itemTypeInList))
+                }
+              }
+            }));
+          }
+
+          fieldConfig.type = listWrapperTypes.get(itemTypeNameInList);
+
+          // 2. Replacing resolver to return `{ size, items }`
+          const originalResolver = fieldConfig.resolve;
+
+          fieldConfig.resolve = (parent, args, ctx, info) => {
+            const value = originalResolver ? originalResolver(parent, args, ctx, info) : parent[fieldName];
+            const items = value || [];
+
+            return {
+              size: items.length,
+              items
+            };
+          };
+
+          // 3. Returning the updated `fieldConfig`
+          return fieldConfig;
+        },
+      });
+    }
+
+    let schema = makeExecutableSchema({
+      typeDefs: `
+        directive @addListWrapper on FIELD_DEFINITION
+
+        type Query {
+          me: Person
+        }
+        type Person {
+          name: String!
+          friends: [Person] @addListWrapper
+        }
+      `,
+      schemaTransforms: [listWrapperTransformer]
+    });
+
+    schema = addMocksToSchema({ schema });
+
+    const result = await graphql(
+      schema,
+      `
+        query {
+          me {
+            friends {
+              items {
+                name
+              }
+            }
+          }
+        }
+      `,
+    );
+
+    const expectedResult: any = {
+      me: {
+        friends: {
+          items: [
+            {
+              name: 'Hello World',
+            },
+            {
+              name: 'Hello World',
+            },
+          ]
+        },
+      }
+    };
+
+    expect(result.data).toEqual(expectedResult);
+  });
 });