fix(image-optimizer): respect updated upstream Cache-Control when reusing cached image

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

@@ -1164,7 +1164,7 @@ export async function imageOptimizer(
     return {
       buffer: previouslyCachedImage.buffer,
       contentType,
-      maxAge: opts?.previousCacheEntry?.cacheControl?.revalidate || maxAge,
+      maxAge,
       etag: previouslyCachedImage.etag,
       upstreamEtag: previouslyCachedImage.upstreamEtag,
     }

test/unit/image-optimizer/image-optimizer-max-age.test.ts

@@ -0,0 +1,113 @@
+/* eslint-env jest */
+import { imageOptimizer, getImageEtag } from 'next/dist/server/image-optimizer'
+import {
+  CachedRouteKind,
+  IncrementalResponseCacheEntry,
+} from 'next/dist/server/response-cache/types'
+import { readFile } from 'fs-extra'
+import { join } from 'path'
+
+const nextConfig = {
+  experimental: {
+    imgOptConcurrency: null,
+    imgOptMaxInputPixels: undefined,
+    imgOptSequentialRead: null,
+    imgOptSkipMetadata: false,
+    imgOptTimeoutInSeconds: 7,
+  },
+  images: {
+    dangerouslyAllowSVG: false,
+    minimumCacheTTL: 60,
+  },
+} as unknown as Parameters<typeof imageOptimizer>[2]
+
+const paramsResult = {
+  href: 'https://example.com/test.jpg',
+  width: 64,
+  quality: 75,
+  mimeType: '',
+} as Parameters<typeof imageOptimizer>[1]
+
+describe('imageOptimizer maxAge with previously cached image', () => {
+  it('reflects the new upstream Cache-Control when reusing an unchanged cached image', async () => {
+    const buffer = await readFile(join(__dirname, './images/test.jpg'))
+    const upstreamEtag = getImageEtag(buffer)
+
+    // The previous cache entry was written when the upstream advertised a long
+    // TTL (1 year). The optimized etag differs from the upstream etag so the
+    // entry is eligible for reuse.
+    const previousCacheEntry = {
+      isStale: true,
+      isMiss: false,
+      isFallback: false,
+      revalidateAfter: 0,
+      cacheControl: { revalidate: 31536000, expire: undefined },
+      value: {
+        kind: CachedRouteKind.IMAGE,
+        upstreamEtag,
+        etag: 'optimized-etag',
+        buffer,
+        extension: 'jpeg',
+      },
+    } as unknown as IncrementalResponseCacheEntry
+
+    // On revalidation the upstream is re-fetched and now advertises a much
+    // shorter TTL. The source bytes are unchanged (same upstream etag) so the
+    // optimized buffer is reused, but the returned maxAge must reflect the new
+    // upstream header (300), not the stale persisted value (31536000).
+    const result = await imageOptimizer(
+      {
+        buffer,
+        contentType: 'image/jpeg',
+        cacheControl: 'max-age=300',
+        etag: upstreamEtag,
+      },
+      paramsResult,
+      nextConfig,
+      { silent: true, previousCacheEntry }
+    )
+
+    // Optimization was skipped: the previously optimized image is reused.
+    expect(result.etag).toBe('optimized-etag')
+    expect(result.upstreamEtag).toBe(upstreamEtag)
+    // The TTL reflects the freshly fetched upstream Cache-Control header.
+    expect(result.maxAge).toBe(300)
+  })
+
+  it('clamps the reused maxAge to minimumCacheTTL', async () => {
+    const buffer = await readFile(join(__dirname, './images/test.jpg'))
+    const upstreamEtag = getImageEtag(buffer)
+
+    const previousCacheEntry = {
+      isStale: true,
+      isMiss: false,
+      isFallback: false,
+      revalidateAfter: 0,
+      cacheControl: { revalidate: 31536000, expire: undefined },
+      value: {
+        kind: CachedRouteKind.IMAGE,
+        upstreamEtag,
+        etag: 'optimized-etag',
+        buffer,
+        extension: 'jpeg',
+      },
+    } as unknown as IncrementalResponseCacheEntry
+
+    // Upstream advertises a TTL below minimumCacheTTL (60), so the result is
+    // clamped up to minimumCacheTTL.
+    const result = await imageOptimizer(
+      {
+        buffer,
+        contentType: 'image/jpeg',
+        cacheControl: 'max-age=5',
+        etag: upstreamEtag,
+      },
+      paramsResult,
+      nextConfig,
+      { silent: true, previousCacheEntry }
+    )
+
+    expect(result.etag).toBe('optimized-etag')
+    expect(result.maxAge).toBe(60)
+  })
+})