From 1f389978343dc472b31ee3865e4068702eab0f21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eduardo=20Bou=C3=A7as?= <mail@eduardoboucas.com>
Date: Wed, 15 Oct 2025 08:50:53 +0100
Subject: [PATCH] fix: make `fetchWithCache` stop throwing on uncacheable
 response

---
 packages/cache/src/fetchwithcache.test.ts | 22 ++++++++++++++++++++++
 packages/cache/src/fetchwithcache.ts      |  5 ++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/packages/cache/src/fetchwithcache.test.ts b/packages/cache/src/fetchwithcache.test.ts
index 555c712c..a1a786d5 100644
--- a/packages/cache/src/fetchwithcache.test.ts
+++ b/packages/cache/src/fetchwithcache.test.ts
@@ -307,4 +307,26 @@ describe('`fetchWithCache`', () => {
     mockFetch.restore()
     expect(mockFetch.fulfilled).toBe(true)
   })
+
+  test('Does not throw an error when response returns a 5xx error', async () => {
+    const mockFetch = new MockFetch()
+      .get({
+        url: 'https://example.netlify/.netlify/cache/https%3A%2F%2Fnetlify.com%2F',
+        response: new Response(null, { status: 404 }),
+      })
+      .get({
+        url: 'https://netlify.com/',
+        response: new Response('Internal Server Error', { status: 500 }),
+      })
+      .inject()
+    const resourceURL = 'https://netlify.com'
+
+    const response = await fetchWithCache(resourceURL)
+
+    expect(response.status).toBe(500)
+    expect(await response.text()).toBe('Internal Server Error')
+
+    mockFetch.restore()
+    expect(mockFetch.fulfilled).toBe(true)
+  })
 })
diff --git a/packages/cache/src/fetchwithcache.ts b/packages/cache/src/fetchwithcache.ts
index 77f7b3f4..9b613aee 100644
--- a/packages/cache/src/fetchwithcache.ts
+++ b/packages/cache/src/fetchwithcache.ts
@@ -129,7 +129,10 @@ export const fetchWithCache: FetchWithCache = async (
   const cacheResponse = new Response(cacheStream, fresh)
   applyHeaders(cacheResponse.headers, cacheHeaders(cacheSettings))
 
-  const cachePut = cache.put(request, cacheResponse)
+  const cachePut = cache.put(request, cacheResponse).catch(() => {
+    // If we fail to cache the response, we want to swallow the error because
+    // we'll still return the result of `fetch`.
+  })
 
   if (onCachePut) {
     await onCachePut(cachePut)