From 327b384938b1fdf44e77c5bd79e91b7fab0aaad4 Mon Sep 17 00:00:00 2001
From: Alejandro Garcia Anglada <aganglada@gmail.com>
Date: Tue, 20 Oct 2020 11:14:00 +0100
Subject: [PATCH] ctx.errors: handles undefined and null values

---
 src/context/errors.test.ts |  7 +++++++
 src/context/errors.ts      | 14 ++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/context/errors.test.ts b/src/context/errors.test.ts
index 7bd2e0239..86be862a0 100644
--- a/src/context/errors.test.ts
+++ b/src/context/errors.test.ts
@@ -60,3 +60,10 @@ test('combines with data in the response JSON body', () => {
     }),
   )
 })
+
+test('bypasses undefined errors', () => {
+  const result = response(errors(undefined), errors(null))
+
+  expect(result.headers.get('content-type')).not.toEqual('application/json')
+  expect(result).toHaveProperty('body', null)
+})
diff --git a/src/context/errors.ts b/src/context/errors.ts
index 0c1dd708a..f82686658 100644
--- a/src/context/errors.ts
+++ b/src/context/errors.ts
@@ -3,10 +3,16 @@ import { ResponseTransformer } from '../response'
 import { json } from './json'
 
 /**
- * Returns a list of GraphQL errors.
+ * Sets a given list of GraphQL errors on the mocked response.
  */
-export const errors = (
-  errorsList: Partial<GraphQLError>[],
-): ResponseTransformer<{ errors: typeof errorsList }> => {
+export const errors = <
+  ErrorsType extends Partial<GraphQLError>[] | null | undefined
+>(
+  errorsList: ErrorsType,
+): ResponseTransformer<{ errors: ErrorsType }> => {
+  if (errorsList == null) {
+    return (res) => res
+  }
+
   return json({ errors: errorsList }, { merge: true })
 }