From 849df82b13ee9b3308a7515dd9edb6dc31662e3a Mon Sep 17 00:00:00 2001
From: Jason Dent <Jason3S@users.noreply.github.com>
Date: Wed, 8 Sep 2021 08:53:16 +0200
Subject: [PATCH] fix: Explicitly look for instance of Error. (#155)

---
 src/helpers/errors.test.ts | 10 +++++++++-
 src/helpers/errors.ts      |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/helpers/errors.test.ts b/src/helpers/errors.test.ts
index 683fb58..44ad50c 100644
--- a/src/helpers/errors.test.ts
+++ b/src/helpers/errors.test.ts
@@ -1,5 +1,11 @@
 import { isError, __testing__ } from './errors';
 
+class MyError extends Error {
+    constructor(msg: string) {
+        super(msg);
+    }
+}
+
 describe('errors', () => {
     test.each`
         value                                   | expected
@@ -10,7 +16,9 @@ describe('errors', () => {
         ${{ message: '', name: '' }}            | ${true}
         ${{ message: '', name: '', stack: '' }} | ${true}
         ${{ message: '', name: '', stack: 5 }}  | ${false}
-    `('isError', ({ value, expected }) => {
+        ${new Error('test error')}              | ${true}
+        ${new MyError('test error')}            | ${true}
+    `('isError $value', ({ value, expected }) => {
         expect(isError(value)).toBe(expected);
     });
 
diff --git a/src/helpers/errors.ts b/src/helpers/errors.ts
index 0e9e07c..097c68e 100644
--- a/src/helpers/errors.ts
+++ b/src/helpers/errors.ts
@@ -18,6 +18,7 @@ const allowStringOrUndefined: AllowedTypes = {
 // };
 
 export function isError(e: unknown): e is Error {
+    if (e instanceof Error) return true;
     if (!e || typeof e !== 'object') return false;
     const ex = <Error>e;
     return typeof ex.name == 'string' && typeof ex.message == 'string' && typeof ex.stack in allowStringOrUndefined;