fix(image): return 502 when upstream request fails

packages/next/src/server/image-optimizer.ts

@@ -561,7 +561,10 @@ export async function fetchExternalImage(
         '"url" parameter is valid but upstream response timed out'
       )
     }
-    throw err
+    throw new ImageError(
+      502,
+      '"url" parameter is valid but upstream request failed'
+    )
   }
 
   const locationHeader = res.headers.get('Location')

test/unit/image-optimizer/fetch-external-image.test.ts

@@ -233,4 +233,21 @@ describe('fetchExternalImage', () => {
       expect(result.buffer.length).toBe(maximumResponseBody)
     })
   })
+  describe('upstream fetch errors', () => {
+    it('should throw a 502 ImageError when the upstream fetch fails', async () => {
+      global.fetch = jest.fn().mockRejectedValue(new Error('fetch failed'))
+
+      const error = await fetchExternalImage(
+        'https://example.com/image.jpg',
+        false,
+        50_000_000
+      ).catch((e) => e)
+
+      expect(error).toBeInstanceOf(ImageError)
+      expect((error as ImageError).statusCode).toBe(502)
+      expect((error as ImageError).message).toBe(
+        '"url" parameter is valid but upstream request failed'
+      )
+    })
+  })
 })