Disable 2mb limit for custom incrementalCacheHandler

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

@@ -65,6 +65,7 @@ export class CacheHandler {
 export class IncrementalCache implements IncrementalCacheType {
   dev?: boolean
   cacheHandler?: CacheHandler
+  isFetchCacherPossible: boolean
   prerenderManifest: PrerenderManifest
   requestHeaders: Record<string, undefined | string | string[]>
   requestProtocol?: 'http' | 'https'
@@ -112,6 +113,8 @@ export class IncrementalCache implements IncrementalCacheType {
     experimental: { ppr: boolean }
   }) {
     const debug = !!process.env.NEXT_PRIVATE_DEBUG_CACHE
+    this.isFetchCacherPossible =
+      !CurCacheHandler || CurCacheHandler instanceof FetchCache
     if (!CurCacheHandler) {
       if (fs && serverDistDir) {
         if (debug) {
@@ -556,7 +559,11 @@ export class IncrementalCache implements IncrementalCacheType {
 
     if (this.dev && !ctx.fetchCache) return
     // fetchCache has upper limit of 2MB per-entry currently
-    if (ctx.fetchCache && JSON.stringify(data).length > 2 * 1024 * 1024) {
+    if (
+      ctx.fetchCache &&
+      this.isFetchCacherPossible &&
+      JSON.stringify(data).length > 2 * 1024 * 1024
+    ) {
       if (this.dev) {
         throw new Error(`fetch for over 2MB of data can not be cached`)
       }

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

@@ -3053,6 +3053,16 @@ createNextDescribe(
         expect(next.cliOutput).toContain('cache-handler get')
         expect(next.cliOutput).toContain('cache-handler set')
       })
+
+      it('should load large data only once when using custom cache handler and force-cache mode', async () => {
+        const browser = await next.browser('/force-cache/large-data')
+        await browser.waitForElementByCss('#content')
+        await browser.refresh()
+        await browser.waitForElementByCss('#content')
+        await browser.refresh()
+        await browser.waitForElementByCss('#content')
+        expect(next.cliOutput.match('Load data').length).toBe(1)
+      })
     }
   }
 )

test/e2e/app-dir/app-static/app/api/large-data/route.js

@@ -0,0 +1,10 @@
+import { NextResponse } from 'next/server'
+
+export async function GET() {
+  console.log('Load data')
+  return NextResponse.json({
+    content: Array.from(new Array(3 * 1024 * 1024))
+      .map(() => 1)
+      .join(''),
+  })
+}

test/e2e/app-dir/app-static/app/force-cache/large-data/page.js

@@ -0,0 +1,13 @@
+export default async function Page() {
+  const resp = await fetch(
+    `http://localhost:${process.env.PORT}/api/large-data`,
+    {
+      cache: 'force-cache',
+    }
+  )
+  const data = await resp.json()
+
+  return <p id="content">{data.content}</p>
+}
+
+export const dynamic = 'force-dynamic'