Don't delete .next folder before a replacement is built

.gitignore

@@ -9,6 +9,7 @@ npm-debug.log
 
 # other
 .next
+.next-*
 
 # coverage
 .nyc_output
@@ -17,4 +18,4 @@ coverage
 # editors
 .idea/*
 *.iml
-*.sublime-*
+*.sublime-*

server/build/clean.js

@@ -1,6 +1,6 @@
 import { resolve } from 'path'
 import del from 'del'
 
-export default function clean (dir) {
-  return del(resolve(dir, '.next'))
+export default function clean (dir, folderName = '.next') {
+  return del(resolve(dir, folderName))
 }

server/build/gzip.js

@@ -3,8 +3,8 @@ import path from 'path'
 import zlib from 'zlib'
 import glob from 'glob-promise'
 
-export default async function gzipAssets (dir) {
-  const nextDir = path.resolve(dir, '.next')
+export default async function gzipAssets (dir, buildFolder = '.next') {
+  const nextDir = path.resolve(dir, buildFolder)
 
   const coreAssets = [
     path.join(nextDir, 'commons.js'),

server/build/index.js

@@ -4,16 +4,19 @@ import path from 'path'
 import webpack from './webpack'
 import clean from './clean'
 import gzipAssets from './gzip'
+import replaceCurrentBuild from './replace'
 
 export default async function build (dir) {
-  const [compiler] = await Promise.all([
-    webpack(dir),
-    clean(dir)
-  ])
+  const distFolder = '.next'
+  const buildFolder = `.next-${uuid.v4()}`
+  const compiler = await webpack(dir, buildFolder)
 
   await runCompiler(compiler)
-  await gzipAssets(dir)
-  await writeBuildId(dir)
+  const oldFolder = await replaceCurrentBuild(dir, buildFolder, distFolder)
+  await gzipAssets(dir, distFolder)
+  await writeBuildId(dir, distFolder)
+
+  clean(dir, oldFolder)
 }
 
 function runCompiler (compiler) {
@@ -34,8 +37,8 @@ function runCompiler (compiler) {
   })
 }
 
-async function writeBuildId (dir) {
-  const buildIdPath = path.resolve(dir, '.next', 'BUILD_ID')
+async function writeBuildId (dir, distFolder) {
+  const buildIdPath = path.resolve(dir, distFolder, 'BUILD_ID')
   const buildId = uuid.v4()
   await fs.writeFile(buildIdPath, buildId, 'utf8')
 }

server/build/replace.js

@@ -0,0 +1,18 @@
+import fs from 'fs'
+import path from 'path'
+import uuid from 'uuid'
+
+export default function replaceCurrentBuild (dir, buildFolder, distFolder) {
+  const distDir = path.resolve(dir, distFolder)
+  const buildDir = path.resolve(dir, buildFolder)
+  const oldDir = path.resolve(dir, `.next-${uuid.v4()}`)
+
+  return new Promise((resolve, reject) => {
+    fs.rename(distDir, oldDir, () => {
+      fs.rename(buildDir, distDir, (err) => {
+        if (err) return reject(err)
+        resolve(oldDir)
+      })
+    })
+  })
+}

server/build/webpack.js

@@ -23,7 +23,7 @@ const interpolateNames = new Map(defaultPages.map((p) => {
   return [join(nextPagesDir, p), `dist/pages/${p}`]
 }))
 
-export default async function createCompiler (dir, { dev = false, quiet = false } = {}) {
+export default async function createCompiler (dir, buildFolder, { dev = false, quiet = false } = {}) {
   dir = resolve(dir)
   const config = getConfig(dir)
   const defaultEntries = dev
@@ -228,7 +228,7 @@ export default async function createCompiler (dir, { dev = false, quiet = false
     context: dir,
     entry,
     output: {
-      path: join(dir, '.next'),
+      path: join(dir, buildFolder || '.next'),
       filename: '[name]',
       libraryTarget: 'commonjs2',
       publicPath: '/_webpack/',

server/hot-reloader.js

@@ -35,7 +35,7 @@ export default class HotReloader {
 
   async start () {
     const [compiler] = await Promise.all([
-      webpack(this.dir, { dev: true, quiet: this.quiet }),
+      webpack(this.dir, null, { dev: true, quiet: this.quiet }),
       clean(this.dir)
     ])