Pass and Check for Error Extensions

CHANGELOG.md

@@ -10,6 +10,8 @@
   [@jure](https://github.com/jure) in [#948](https://github.com/apollographql/graphql-tools/pull/948)
 * Stop automatically shallow cloning (via object spread syntax) transformed subscription results. Transformed subscription results are not always objects, which means object spreading can lead to invalid results.  <br/>
   [@ericlewis](https://github.com/ericlewis) in [#928](https://github.com/apollographql/graphql-tools/pull/928)  
+* Re-use errors with an `extensions` property to make compatible with Apollo Server and it's built-in errors.  <br/>
+  [@edorsey](https://github.com/edorsey) in [#925](https://github.com/apollographql/graphql-tools/pull/925)
 * Documentation updates.  <br/>
   [@Amorites](https://github.com/Amorites) in [#944](https://github.com/apollographql/graphql-tools/pull/944)  <br/>
   [@trevor-scheer](https://github.com/trevor-scheer) in [#946](https://github.com/apollographql/graphql-tools/pull/946)  <br/>

src/stitching/errors.ts

@@ -119,5 +119,5 @@ function concatErrors(errors: Error[]) {
 }
 
 function hasResult(error: any) {
-  return error.result || (error.originalError && error.originalError.result);
+  return error.result || error.extensions || (error.originalError && error.originalError.result);
 }

src/test/testErrors.ts

@@ -12,6 +12,14 @@ class ErrorWithResult extends Error {
   }
 }
 
+class ErrorWithExtensions extends Error {
+  public extensions: any;
+  constructor(message: string, code: string) {
+    super(message);
+    this.extensions = { code };
+  }
+}
+
 describe('Errors', () => {
   describe('getErrorsFromParent', () => {
     it('should return OWN error kind if path is not defined', () => {
@@ -44,6 +52,19 @@ describe('Errors', () => {
       }
     });
 
+    it('persists single error with extensions', () => {
+      const result = {
+        errors: [new ErrorWithExtensions('Test error', 'UNAUTHENTICATED')]
+      };
+      try {
+        checkResultAndHandleErrors(result, {} as GraphQLResolveInfo, 'responseKey');
+      } catch (e) {
+        assert.equal(e.message, 'Test error');
+        assert.equal(e.extensions && e.extensions.code, 'UNAUTHENTICATED');
+        assert.isUndefined(e.originalError.errors);
+      }
+    });
+
     it('persists original errors without a result', () => {
       const result = {
         errors: [new Error('Test error')]
@@ -61,7 +82,7 @@ describe('Errors', () => {
       }
     });
 
-    it('combines errors and perists the original errors', () => {
+    it('combines errors and persists the original errors', () => {
       const result = {
         errors: [new Error('Error1'), new Error('Error2')]
       };