feat: cache .next/cache between builds

Author: lindsaylevine

helpers/cacheBuild.js

@@ -0,0 +1,32 @@
+const path = require('path')
+
+const DEFAULT_DIST_DIR = '.next'
+
+// Account for possible custom distDir
+const getPath = (distDir, source) => {
+  return path.join(distDir || DEFAULT_DIST_DIR, source)
+}
+
+const restoreCache = async ({ cache, distDir }) => {
+  const cacheDir = getPath(distDir, 'cache')
+  if (await cache.restore(cacheDir)) {
+    console.log('Next.js cache restored.')
+  } else {
+    console.log('No Next.js cache to restore.')
+  }
+}
+
+const saveCache = async ({ cache, distDir }) => {
+  const cacheDir = getPath(distDir, 'cache')
+  const buildManifest = getPath(distDir, 'build-manifest.json')
+  if (await 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

@@ -9,6 +9,7 @@ const validateNextUsage = require('./helpers/validateNextUsage')
 const doesNotNeedPlugin = require('./helpers/doesNotNeedPlugin')
 const getNextConfig = require('./helpers/getNextConfig')
 const copyUnstableIncludedDirs = require('./helpers/copyUnstableIncludedDirs')
+const { restoreCache, saveCache } = require('./helpers/cacheBuild')
 
 const pWriteFile = util.promisify(fs.writeFile)
 
@@ -27,6 +28,9 @@ module.exports = {
       return failBuild('Could not find a package.json for this project')
     }
 
+    const nextConfig = await getNextConfig(utils.failBuild)
+    await restoreCache({ cache: utils.cache, distDir: nextConfig.distDir })
+
     if (await doesNotNeedPlugin({ netlifyConfig, packageJson, failBuild })) {
       return
     }
@@ -60,12 +64,14 @@ module.exports = {
 
     await nextOnNetlify({ functionsDir: FUNCTIONS_SRC, publishDir: PUBLISH_DIR })
   },
+
   async onPostBuild({ netlifyConfig, packageJson, constants: { FUNCTIONS_DIST }, utils }) {
     if (await doesNotNeedPlugin({ netlifyConfig, packageJson, utils })) {
       return
     }
 
     const nextConfig = await getNextConfig(utils.failBuild)
+    await saveCache({cache: utils.cache, distDir: nextConfig.distDir })
     copyUnstableIncludedDirs({ nextConfig, functionsDist: FUNCTIONS_DIST })
   },
 }

test/index.js

@@ -18,6 +18,10 @@ const utils = {
       throw new Error(message)
     },
   },
+  cache: {
+    save() {},
+    restore() {},
+  }
 }
 
 // Temporary switch cwd