Cache `.next/cache/` between builds

[ehmicky]

We could use the cache utility to cache .next/cache between builds, to speed up Next.js builds.

An existing plugin is already doing it (source code). Since that plugin allows users to customize the path to .next/cache/, it could still be useful for the few users who need that. @lindsaylevine Do you think using a custom file path for .next/ is common?

Without that case in mind, adding this would probably look like this:

const CACHE_DIR = '.next/cache/'
const BUILD_MANIFEST = '.next/build-manifest.json'

module.exports = {
	async onPreBuild({ utils }) {
		if (await utils.cache.restore(CACHE_DIR)) {
			console.log('Next.js cache restored.')
		} else {
			console.log('No Next.js cache to restore')
		}
	},
	async onPostBuild({ utils }) {
		if (await utils.cache.save(CACHE_DIR, { digests: [BUILD_MANIFEST] })) {
			console.log('Next.js cache saved.')
		} else {
			console.log('No Next.js cache to save.')
		}
	}
}

What do you think?

[lindsaylevine]

yes this would be an excellent addition after everything else is in place!!