Provide a way to set custom cache directory

[kirill-konshin]

Link to the code that reproduces this issue

https://github.com/kirill-konshin/next-electron-rsc/tree/main/demo

To Reproduce

1. Clone the repo
2. cd demo
3. yarn build
4. yarn open

Current vs. Expected behavior

Next.js is in standalone mode here, and is bundled using electron-builder.

Since the .next/standalone/demo/ is part of files, it becomes part of the ASAR.

When the Electron runs as a build, Next.js emits following error:

 ⨯ Failed to write image to cache 24-d7GMv9Put-b8LiQHcADsQ3iL099cDsuFLFsgj0LE Error: ENOTDIR: not a directory, mkdir '/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/.next/cache/images/24-d7GMv9Put-b8LiQHcADsQ3iL099cDsuFLFsgj0LE'
    at async writeToCacheDir (/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/node_modules/next/dist/server/image-optimizer.js:213:5)
    at async ImageOptimizerCache.set (/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/node_modules/next/dist/server/image-optimizer.js:507:13)
    at async (/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/node_modules/next/dist/server/response-cache/index.js:128:25)
    at async (/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/node_modules/next/dist/lib/batcher.js:45:32) {
  errno: -20,
  code: 'ENOTDIR',
  syscall: 'mkdir',
  path: '/x/demo/dist/mac-arm64/Next Electron RSC.app/Contents/Resources/app.asar/.next/standalone/demo/.next/cache/images/24-d7GMv9Put-b8LiQHcADsQ3iL099cDsuFLFsgj0LE'
}

So either ASAR is not writable at all (https://www.electronjs.org/docs/latest/tutorial/asar-archives#archives-are-read-only) the solution could be to provide alternative cacheDir outside of ASAR: https://github.com/vercel/next.js/blob/canary/packages/next/src/server/image-optimizer.ts#L372

I tried opting cache path out of ASAR, did not work for a different reason: electron-userland/electron-builder#7264

Original issue: kirill-konshin/next-electron-rsc#3

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.0.0: Tue Sep 24 23:39:07 PDT 2024; root:xnu-11215.1.12~1/RELEASE_ARM64_T6000
  Available memory (MB): 65536
  Available CPU cores: 10
Binaries:
  Node: 23.0.0
  npm: 10.9.0
  Yarn: 4.5.1
  pnpm: N/A
Relevant Packages:
  next: 15.0.2
  eslint-config-next: 15.0.2
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.6.3
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Image (next/image)

Which stage(s) are affected? (Select all that apply)

Other (Deployed)

Additional context

No response

[samcx]

@kirill-konshin Have you tried taking a look at the cacheHandler config → https://nextjs.org/docs/app/api-reference/next-config-js/incrementalCacheHandlerPath?

[kirill-konshin]

Not sure if this one apply because it caches in memory, not the disk cache for images.

https://github.com/vercel/next.js/blob/canary/packages/next/src/server/image-optimizer.ts#L378 has no mentions of cache handler, and has fixed path for cache.