Add stats config option

packages/next/build/webpack-config.ts

@@ -43,6 +43,7 @@ import { build as buildConfiguration } from './webpack/config'
 import { __overrideCssConfiguration } from './webpack/config/blocks/css/overrideCssConfiguration'
 import { pluginLoaderOptions } from './webpack/loaders/next-plugin-loader'
 import BuildManifestPlugin from './webpack/plugins/build-manifest-plugin'
+import BuildStatsPlugin from './webpack/plugins/build-stats-plugin'
 import ChunkNamesPlugin from './webpack/plugins/chunk-names-plugin'
 import { CssMinimizerPlugin } from './webpack/plugins/css-minimizer-plugin'
 import { JsConfigPathsPlugin } from './webpack/plugins/jsconfig-paths-plugin'
@@ -1109,6 +1110,11 @@ export default async function getBaseWebpackConfig(
           buildId,
           rewrites,
         }),
+      !isServer &&
+        config.experimental.stats &&
+        new BuildStatsPlugin({
+          distDir,
+        }),
       new ProfilingPlugin(),
       config.experimental.optimizeFonts &&
         !dev &&

packages/next/build/webpack/plugins/build-stats-plugin.ts

@@ -0,0 +1,48 @@
+import fs from 'fs'
+import path from 'path'
+// @ts-ignore no types package
+import bfj from 'next/dist/compiled/bfj'
+import { spans } from './profiling-plugin'
+import { webpack } from 'next/dist/compiled/webpack/webpack'
+import { tracer, traceAsyncFn } from '../../tracer'
+
+// This plugin creates a stats.json for a build when enabled
+export default class BuildStatsPlugin {
+  private distDir: string
+
+  constructor(options: { distDir: string }) {
+    this.distDir = options.distDir
+  }
+
+  apply(compiler: webpack.Compiler) {
+    compiler.hooks.done.tapAsync(
+      'NextJsBuildStats',
+      async (stats, callback) => {
+        tracer.withSpan(spans.get(compiler), async () => {
+          try {
+            const writeStatsSpan = tracer.startSpan('NextJsBuildStats')
+            await traceAsyncFn(writeStatsSpan, () => {
+              return new Promise((resolve, reject) => {
+                const statsJson = stats.toJson({
+                  source: false,
+                })
+                const fileStream = fs.createWriteStream(
+                  path.join(this.distDir, 'next-stats.json')
+                )
+                const jsonStream = bfj.streamify(statsJson)
+                jsonStream.pipe(fileStream)
+                jsonStream.on('error', reject)
+                fileStream.on('error', reject)
+                jsonStream.on('dataError', reject)
+                fileStream.on('close', resolve)
+              })
+            })
+            callback()
+          } catch (err) {
+            callback(err)
+          }
+        })
+      }
+    )
+  }
+}

packages/next/compiled/bfj/package.json

@@ -0,0 +1 @@
+{"name":"bfj","main":"index.js","author":"Phil Booth (https://gitlab.com/philbooth)","license":"MIT"}

packages/next/next-server/server/config.ts

@@ -87,6 +87,7 @@ const defaultConfig: NextConfig = {
     optimizeCss: false,
     scrollRestoration: false,
     scriptLoader: false,
+    stats: !!process.env.VERCEL_ANALYTICS_ID,
   },
   future: {
     strictPostcssConfiguration: false,

packages/next/package.json

@@ -178,6 +178,7 @@
     "babel-plugin-dynamic-import-node": "2.3.3",
     "babel-plugin-transform-define": "2.0.0",
     "babel-plugin-transform-react-remove-prop-types": "0.4.24",
+    "bfj": "7.0.2",
     "cacache": "15.0.5",
     "cache-loader": "4.1.0",
     "ci-info": "watson/ci-info#f43f6a1cefff47fb361c88cf4b943fdbcaafe540",

packages/next/taskfile.js

@@ -143,6 +143,14 @@ export async function ncc_babel_bundle_packages(task, opts) {
     .target('compiled/babel/')
 }
 
+// eslint-disable-next-line camelcase
+externals['bfj'] = 'next/dist/compiled/bfj'
+export async function ncc_bfj(task, opts) {
+  await task
+    .source(opts.src || relative(__dirname, require.resolve('bfj')))
+    .ncc({ packageName: 'bfj' })
+    .target('compiled/bfj')
+}
 // eslint-disable-next-line camelcase
 externals['cacache'] = 'next/dist/compiled/cacache'
 export async function ncc_cacache(task, opts) {
@@ -672,6 +680,7 @@ export async function ncc(task) {
       'ncc_async_sema',
       'ncc_babel_bundle',
       'ncc_babel_bundle_packages',
+      'ncc_bfj',
       'ncc_cacache',
       'ncc_cache_loader',
       'ncc_ci_info',

test/integration/build-stats/next.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  experimental: {
+    stats: true,
+  },
+}

test/integration/build-stats/pages/index.js

@@ -0,0 +1,3 @@
+export default function Index(props) {
+  return <p>Hello world</p>
+}

test/integration/build-stats/test/index.test.js

@@ -0,0 +1,20 @@
+/* eslint-env jest */
+
+import fs from 'fs-extra'
+import { join } from 'path'
+import { nextBuild } from 'next-test-utils'
+
+jest.setTimeout(1000 * 60 * 1)
+
+const appDir = join(__dirname, '../')
+const statsPath = join(appDir, '.next/next-stats.json')
+
+describe('Build Stats', () => {
+  it('outputs next-stats.json when enabled', async () => {
+    await nextBuild(appDir)
+    expect(await fs.pathExists(statsPath)).toBe(true)
+
+    const statsData = await fs.readFile(statsPath, 'utf8')
+    JSON.parse(statsData)
+  })
+})

test/integration/production/test/index.test.js

@@ -782,6 +782,10 @@ describe('Production Usage', () => {
     expect(existsSync(join(appDir, '.next', 'profile-events.json'))).toBe(false)
   })
 
+  it('should not emit stats', async () => {
+    expect(existsSync(join(appDir, '.next', 'next-stats.json'))).toBe(false)
+  })
+
   it('should contain the Next.js version in window export', async () => {
     let browser
     try {

yarn.lock

@@ -4016,6 +4016,16 @@ before-after-hook@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/before-after-hook/-/before-after-hook-2.1.0.tgz#b6c03487f44e24200dd30ca5e6a1979c5d2fb635"
 
+bfj@7.0.2:
+  version "7.0.2"
+  resolved "https://registry.yarnpkg.com/bfj/-/bfj-7.0.2.tgz#1988ce76f3add9ac2913fd8ba47aad9e651bfbb2"
+  integrity sha512-+e/UqUzwmzJamNF50tBV6tZPTORow7gQ96iFow+8b562OdMpEK0BcJEq2OSPEDmAbSMBQ7PKZ87ubFkgxpYWgw==
+  dependencies:
+    bluebird "^3.5.5"
+    check-types "^11.1.1"
+    hoopy "^0.1.4"
+    tryer "^1.0.1"
+
 big.js@^5.2.2:
   version "5.2.2"
   resolved "https://registry.yarnpkg.com/big.js/-/big.js-5.2.2.tgz#65f0af382f578bcdc742bd9c281e9cb2d7768328"
@@ -4619,6 +4629,11 @@ chardet@^0.7.0:
   version "0.7.0"
   resolved "https://registry.yarnpkg.com/chardet/-/chardet-0.7.0.tgz#90094849f0937f2eedc2425d0d28a9e5f0cbad9e"
 
+check-types@^11.1.1:
+  version "11.1.2"
+  resolved "https://registry.yarnpkg.com/check-types/-/check-types-11.1.2.tgz#86a7c12bf5539f6324eb0e70ca8896c0e38f3e2f"
+  integrity sha512-tzWzvgePgLORb9/3a0YenggReLKAIb2owL03H2Xdoe5pKcUyWRSEQ8xfCar8t2SIAuEDwtmx2da1YB52YuHQMQ==
+
 cheerio@0.22.0:
   version "0.22.0"
   resolved "https://registry.yarnpkg.com/cheerio/-/cheerio-0.22.0.tgz#a9baa860a3f9b595a6b81b1a86873121ed3a269e"
@@ -7877,6 +7892,11 @@ homedir-polyfill@^1.0.0:
   dependencies:
     parse-passwd "^1.0.0"
 
+hoopy@^0.1.4:
+  version "0.1.4"
+  resolved "https://registry.yarnpkg.com/hoopy/-/hoopy-0.1.4.tgz#609207d661100033a9a9402ad3dea677381c1b1d"
+  integrity sha512-HRcs+2mr52W0K+x8RzcLzuPPmVIKMSv97RGHy0Ea9y/mpcaK+xTrjICA04KAHi4GRzxliNqNJEFYWHghy3rSfQ==
+
 hosted-git-info@^2.1.4, hosted-git-info@^2.7.1:
   version "2.8.5"
   resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.8.5.tgz#759cfcf2c4d156ade59b0b2dfabddc42a6b9c70c"
@@ -15507,6 +15527,11 @@ trough@^1.0.0:
   dependencies:
     glob "^7.1.2"
 
+tryer@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/tryer/-/tryer-1.0.1.tgz#f2c85406800b9b0f74c9f7465b81eaad241252f8"
+  integrity sha512-c3zayb8/kWWpycWYg87P71E1S1ZL6b6IJxfb5fvsUgsf0S2MVGaDhDXXjDMpdCpfWXqptc+4mXwmiy1ypXqRAA==
+
 ts-pnp@^1.1.6:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/ts-pnp/-/ts-pnp-1.2.0.tgz#a500ad084b0798f1c3071af391e65912c86bca92"