Bugfix - @After middleware changing return type

CHANGELOG.md

@@ -16,6 +16,7 @@
 - Improved tests by adding @Root ones - [#52](https://github.com/indigotech/graphql-schema-decorator/pull/52) - [@babbarankit](https://github.com/babbarankit)
 - Added @InterfaceType decorator - [#46](https://github.com/indigotech/graphql-schema-decorator/pull/46) - [@felipesabino](https://github.com/felipesabino)
 - Added @After middleware decorator - [#56](https://github.com/indigotech/graphql-schema-decorator/pull/56) - [@marcelorisse](https://github.com/marcelorisse)
+- Bugfix - @After middleware changing return type - [#58](https://github.com/indigotech/graphql-schema-decorator/pull/58) - [@felipesabino](https://github.com/felipesabino)
 
 ### Breaking changes
 

src/specs/functional.spec.ts

@@ -197,6 +197,12 @@ describe('Functional', function () {
 
     describe('After Middleware', function () {
 
+      @D.ObjectType()
+      class ChangedReturnType {
+        @D.Field({ nonNull: true })
+        data: string;
+      }
+
       @D.ObjectType()
       class QueryType {
         @D.Field({ type: graphql.GraphQLString })
@@ -207,6 +213,24 @@ describe('Functional', function () {
           return 'Hello, world!';
         }
 
+        @D.Field({ type: ChangedReturnType })
+        @D.After({
+          middleware: async (
+            context,
+            args,
+            result: Promise<string>,
+            next: (error?: Error, value?: ChangedReturnType) => void,
+          ) => {
+            let changedReturnType = {
+              data: (await result),
+            };
+            next(null, changedReturnType);
+          },
+        })
+        async changeReturnType(): Promise<string> {
+          return 'Hello, world!';
+        }
+
         @D.Field({ type: graphql.GraphQLString })
         @D.After({
           middleware: (context, args, result, next) => {
@@ -244,6 +268,7 @@ describe('Functional', function () {
         async callError(): Promise<string> {
           return 'Hello, world!';
         }
+
       }
 
       @D.Schema()
@@ -291,6 +316,12 @@ describe('Functional', function () {
         assert(result.errors[0].message === 'Error from middleware');
       });
 
+      it('resolves @Field decorated with @After Middleware changing result type', async function () {
+        const schema = schemaFactory(SchemaType);
+        const result = await graphql.graphql(schema, `query { changeReturnType { data } }`);
+        assert(result.data.changeReturnType.data === 'Hello, world!');
+      });
+
     });
 
     describe('Union', function () {

src/type-factory/field.type-factory.ts

@@ -158,18 +158,22 @@ export function resolverFactory(
     }
 
     if (metadata.after) {
-      let next: (error?: Error) => void = (error?: Error, value?: any): any => {
-        if (error) {
-          throw error;
-        } else if (typeof (value) !== 'undefined') {
-          result = value;
-        }
-        return result;
-      };
-      metadata.after.middleware.call(fieldParentClass, context, args, result, next);
+      return new Promise((resolve, reject) => {
+        let next: (error?: Error) => void = (error?: Error, value?: any): any => {
+          if (error) {
+            reject(error);
+          } else if (typeof (value) !== 'undefined') {
+            resolve(value);
+          } else {
+            resolve(result);
+          }
+        };
+        metadata.after.middleware.call(fieldParentClass, context, args, result, next);
+      });
+    } else {
+      return result;
     }
 
-    return result;
   };
 
   return {