returns a FetchError when the response is not ok

Author: jarvisjiang

src/fetch/defines.ts

@@ -55,4 +55,23 @@ export interface FetchInit extends RequestInit {
      * Specifies the maximum time in milliseconds to wait for the fetch request to complete.
      */
     timeout?: number;
+}
+
+/**
+ * Represents an error that occurred during a fetch operation when the response is not ok.
+ */
+export class FetchError extends Error {
+    /**
+     * The name of the error.
+     */
+    name = 'FetchError';
+    /**
+     * The status code of the response.
+     */
+    status = 0;
+
+    constructor(message: string, status: number) {
+        super(message);
+        this.status = status;
+    }
 }

src/fetch/fetch.ts

@@ -1,7 +1,7 @@
 import { Err, Ok } from 'happy-rusty';
 import invariant from 'tiny-invariant';
 import { TIMEOUT_ERROR } from './constants.ts';
-import type { FetchInit, FetchResponse, FetchTask } from './defines.ts';
+import { FetchError, type FetchInit, type FetchResponse, type FetchTask } from './defines.ts';
 
 /**
  * Fetches a resource from the network as a text string and returns a `FetchTask` representing the operation.
@@ -160,7 +160,7 @@ export function fetchT<T>(url: string | URL, init?: FetchInit): FetchTask<T> | F
 
         if (!res.ok) {
             await res.body?.cancel();
-            return Err(new Error(`fetch status: ${ res.status }`));
+            return Err(new FetchError(res.statusText, res.status));
         }
 
         switch (responseType) {

tests/fetch.test.ts

@@ -1,5 +1,5 @@
 import { assert, assertThrows } from '@std/assert';
-import { ABORT_ERROR, fetchT, TIMEOUT_ERROR } from '../src/mod.ts';
+import { ABORT_ERROR, FetchError, fetchT, TIMEOUT_ERROR } from '../src/mod.ts';
 
 Deno.test('fetch', async (t) => {
     const mockServer = 'https://fakestoreapi.com';
@@ -195,8 +195,10 @@ Deno.test('fetch', async (t) => {
         }
     });
 
-    await t.step('Fetch fail', async () => {
+    await t.step('Fetch not found', async () => {
         const err: Error = (await fetchT(mockNotFound)).unwrapErr();
-        assert(err.message.includes('404'));
+        assert(err.name === 'FetchError');
+        assert(err.message === 'Not Found');
+        assert((err as FetchError).status === 404);
     });
 });