feat: cache .next/cache between builds

Author: lindsaylevine

helpers/cacheBuild.js

@@ -0,0 +1,33 @@
+const path = require('path')
+
+const DEFAULT_DIST_DIR = '.next'
+
+// Give advanced/monorepo users the ability to point to their custom build & dist dirs
+const getPath = ({ buildDir, distDir, source }) => {
+  const mainPath = path.join(distDir || DEFAULT_DIST_DIR, source)
+  return buildDir ? path.join(buildDir, mainPath) : mainPath
+}
+
+const restoreCache = async ({ inputs, utils }) => {
+  const cacheDir = getPath({ ...inputs, source: 'cache' })
+  if (await utils.cache.restore(cacheDir)) {
+    console.log('Next.js cache restored.')
+  } else {
+    console.log('No Next.js cache to restore.')
+  }
+}
+
+const saveCache = async ({ inputs, utils }) => {
+  const cacheDir = getPath({ ...inputs, source: 'cache' })
+  const buildManifest = getPath({ ...inputs, source: 'build-manifest.json' })
+  if (await utils.cache.save(cacheDir, { digests: [buildManifest] })) {
+    console.log('Next.js cache saved.')
+  } else {
+    console.log('No Next.js cache to save.')
+  }
+}
+
+module.exports = {
+  restoreCache,
+  saveCache,
+}

helpers/isStaticExportProject.js

@@ -17,7 +17,7 @@ const isStaticExportProject = ({ build, scripts }) => {
 
   if (isStaticExport) {
     console.log(
-      `Static HTML export Next.js projects do not require this plugin. Check your project's build command for 'next export'.`,
+      'NOTE: Static HTML export Next.js projects (projects that use `next export`) do not require most of this plugin. For these sites, this plugin *only* caches builds.',
     )
   }
 

index.js

@@ -7,6 +7,7 @@ const nextOnNetlify = require('./src/index.js')
 
 const validateNextUsage = require('./helpers/validateNextUsage')
 const doesNotNeedPlugin = require('./helpers/doesNotNeedPlugin')
+const { restoreCache, saveCache } = require('./helpers/cacheBuild')
 
 const pWriteFile = util.promisify(fs.writeFile)
 
@@ -15,7 +16,7 @@ const pWriteFile = util.promisify(fs.writeFile)
 // - Between the build and postbuild steps, any functions are bundled
 
 module.exports = {
-  async onPreBuild({ netlifyConfig, packageJson, utils }) {
+  async onPreBuild({ inputs, netlifyConfig, packageJson, utils }) {
     const { failBuild } = utils.build
 
     validateNextUsage(failBuild)
@@ -25,6 +26,8 @@ module.exports = {
       return failBuild('Could not find a package.json for this project')
     }
 
+    await restoreCache({ inputs, utils })
+
     if (await doesNotNeedPlugin({ netlifyConfig, packageJson, failBuild })) {
       return
     }
@@ -58,6 +61,9 @@ module.exports = {
 
     await nextOnNetlify({ functionsDir: FUNCTIONS_SRC, publishDir: PUBLISH_DIR })
   },
+  async onPostBuild({ inputs }) {
+    await saveCache({ inputs, utils })
+  },
 }
 
 const DEFAULT_FUNCTIONS_SRC = 'netlify/functions'