fix(fetch-cache): add check for updated tags when checking same cache key (#63547)

## Why?

When we fetch the same cache key (URL) but add an additional tag, the
revalidation does not re-fetch correctly (the bug just uses in-memory
cache again) when deployed.

:repro: →
https://github.com/lostip/nextjs-revalidation-demo/tree/main

---------

Co-authored-by: Ethan Arrowood <ethan@arrowood.dev>

Author: samcx

packages/next/src/server/lib/incremental-cache/fetch-cache.ts

@@ -28,6 +28,21 @@ export default class FetchCache implements CacheHandler {
   private cacheEndpoint?: string
   private debug: boolean
 
+  private hasMatchingTags(arr1: string[], arr2: string[]) {
+    if (arr1.length !== arr2.length) return false
+
+    const set1 = new Set(arr1)
+    const set2 = new Set(arr2)
+
+    if (set1.size !== set2.size) return false
+
+    for (let tag of set1) {
+      if (!set2.has(tag)) return false
+    }
+
+    return true
+  }
+
   static isAvailable(ctx: {
     _requestHeaders: CacheHandlerContext['_requestHeaders']
   }) {
@@ -168,8 +183,13 @@ export default class FetchCache implements CacheHandler {
     // on successive requests
     let data = memoryCache?.get(key)
 
-    // get data from fetch cache
-    if (!data && this.cacheEndpoint) {
+    const hasFetchKindAndMatchingTags =
+      data?.value?.kind === 'FETCH' &&
+      this.hasMatchingTags(tags ?? [], data.value.tags ?? [])
+
+    // Get data from fetch cache. Also check if new tags have been
+    // specified with the same cache key (fetch URL)
+    if (this.cacheEndpoint && (!data || !hasFetchKindAndMatchingTags)) {
       try {
         const start = Date.now()
         const fetchParams: NextFetchCacheParams = {
@@ -220,6 +240,16 @@ export default class FetchCache implements CacheHandler {
           throw new Error(`invalid cache value`)
         }
 
+        // if new tags were specified, merge those tags to the existing tags
+        if (cached.kind === 'FETCH') {
+          cached.tags ??= []
+          for (const tag of tags ?? []) {
+            if (!cached.tags.include(tag)) {
+              cached.tag.push(tag)
+            }
+          }
+        }
+
         const cacheState = res.headers.get(CACHE_STATE_HEADER)
         const age = res.headers.get('age')
 

test/e2e/app-dir/app-static/app-static.test.ts

@@ -49,6 +49,49 @@ createNextDescribe(
       })
     })
 
+    if (isNextDeploy) {
+      describe('new tags have been specified on subsequent fetch', () => {
+        it('should not fetch from memory cache', async () => {
+          const res1 = await next.fetch('/specify-new-tags/one-tag')
+          expect(res1.status).toBe(200)
+
+          const res2 = await next.fetch('/specify-new-tags/two-tags')
+          expect(res2.status).toBe(200)
+
+          const html1 = await res1.text()
+          const html2 = await res2.text()
+          const $1 = cheerio.load(html1)
+          const $2 = cheerio.load(html2)
+
+          const data1 = $1('#page-data').text()
+          const data2 = $2('#page-data').text()
+          expect(data1).not.toBe(data2)
+        })
+
+        it('should not fetch from memory cache after revalidateTag is used', async () => {
+          const res1 = await next.fetch('/specify-new-tags/one-tag')
+          expect(res1.status).toBe(200)
+
+          const revalidateRes = await next.fetch(
+            '/api/revlidate-tag-node?tag=thankyounext'
+          )
+          expect((await revalidateRes.json()).revalidated).toBe(true)
+
+          const res2 = await next.fetch('/specify-new-tags/two-tags')
+          expect(res2.status).toBe(200)
+
+          const html1 = await res1.text()
+          const html2 = await res2.text()
+          const $1 = cheerio.load(html1)
+          const $2 = cheerio.load(html2)
+
+          const data1 = $1('#page-data').text()
+          const data2 = $2('#page-data').text()
+          expect(data1).not.toBe(data2)
+        })
+      })
+    }
+
     if (isNextStart) {
       it('should propagate unstable_cache tags correctly', async () => {
         const meta = JSON.parse(
@@ -717,6 +760,10 @@ createNextDescribe(
             "route-handler/revalidate-360-isr/route.js",
             "route-handler/revalidate-360/route.js",
             "route-handler/static-cookies/route.js",
+            "specify-new-tags/one-tag/page.js",
+            "specify-new-tags/one-tag/page_client-reference-manifest.js",
+            "specify-new-tags/two-tags/page.js",
+            "specify-new-tags/two-tags/page_client-reference-manifest.js",
             "ssg-draft-mode.html",
             "ssg-draft-mode.rsc",
             "ssg-draft-mode/[[...route]]/page.js",

test/e2e/app-dir/app-static/app/specify-new-tags/one-tag/page.tsx

@@ -0,0 +1,13 @@
+export const dynamic = 'force-dynamic'
+
+export default async function Page() {
+  const data = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random?sam=iam',
+    {
+      cache: 'force-cache',
+      next: { tags: ['thankyounext'] },
+    }
+  ).then((res) => res.text())
+
+  return <p id="page-data">data: {data}</p>
+}

test/e2e/app-dir/app-static/app/specify-new-tags/two-tags/page.tsx

@@ -0,0 +1,13 @@
+export const dynamic = 'force-dynamic'
+
+export default async function Page() {
+  const data = await fetch(
+    'https://next-data-api-endpoint.vercel.app/api/random?sam=iam',
+    {
+      cache: 'force-cache',
+      next: { tags: ['thankyounext', 'justputit'] },
+    }
+  ).then((res) => res.text())
+
+  return <p id="page-data">data: {data}</p>
+}