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Improve compile time on large application (#50792)
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## What?

While investigating slow compilation for a page on vercel.com in
development I found that there was close to 10 seconds of time
unaccounted for in `.next/trace`. Ran a profile and found that time was
spent in watchpack `batch`, specifically calling `close` many times.
When I tried to debug this further by running unbundled webpack I
noticed the same issue didn't exists.

### Before

<img width="1329" alt="Before"
src="https://github.com/vercel/next.js/assets/6324199/9ace4628-db04-4de7-993f-65aef9dffc55">

### After

<img width="1278" alt="After"
src="https://github.com/vercel/next.js/assets/6324199/55d5e58b-4a27-4235-8dea-723a7a78c117">

## Raw numbers

<table>
<tr>
 <td>Before</td>
 <td>After</td>
 <td>Delta</td>
 <td>Delta (percent)</td>
</tr>
<tr>
 <td>13840 ms</td>
 <td>3580 ms</td>
 <td>-10260 ms</td>
  <td>-74.13%</td>
</tr>
</table>

## How?

Investigated further and found that specifically not minifying watchpack
solved the issue.

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timneutkens committed Jun 5, 2023
1 parent 886b389 commit 8ab38ce
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Showing 9 changed files with 18 additions and 20 deletions.
1 change: 1 addition & 0 deletions packages/next/package.json
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,7 @@
"caniuse-lite": "^1.0.30001406",
"postcss": "8.4.14",
"styled-jsx": "5.1.1",
"watchpack": "2.4.0",
"zod": "3.21.4"
},
"peerDependencies": {
Expand Down
6 changes: 4 additions & 2 deletions packages/next/src/cli/next-dev.ts
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ import { findPagesDir } from '../lib/find-pages-dir'
import { findRootDir } from '../lib/find-root'
import { fileExists, FileType } from '../lib/file-exists'
import { getNpxCommand } from '../lib/helpers/get-npx-command'
import Watchpack from 'next/dist/compiled/watchpack'
import Watchpack from 'watchpack'
import stripAnsi from 'next/dist/compiled/strip-ansi'
import { getPossibleInstrumentationHookFilenames } from '../build/worker'

Expand Down Expand Up @@ -479,7 +479,9 @@ const nextDev: CliCommand = async (argv) => {
}

previousInstrumentationFiles.clear()
knownFiles.forEach((_, key) => previousInstrumentationFiles.add(key))
knownFiles.forEach((_: any, key: any) =>
previousInstrumentationFiles.add(key)
)
})

const projectFolderWatcher = new Watchpack({
Expand Down
2 changes: 1 addition & 1 deletion packages/next/src/compiled/sass-loader/cjs.js

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1 change: 0 additions & 1 deletion packages/next/src/compiled/watchpack/watchpack.js

This file was deleted.

2 changes: 1 addition & 1 deletion packages/next/src/compiled/webpack/bundle5.js

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4 changes: 2 additions & 2 deletions packages/next/src/server/dev/next-dev-server.ts
Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ import fs from 'fs'
import { Worker } from 'next/dist/compiled/jest-worker'
import findUp from 'next/dist/compiled/find-up'
import { join as pathJoin, relative, resolve as pathResolve, sep } from 'path'
import Watchpack from 'next/dist/compiled/watchpack'
import Watchpack from 'watchpack'
import { ampValidation } from '../../build/output'
import {
INSTRUMENTATION_HOOK_FILENAME,
Expand Down Expand Up @@ -128,7 +128,7 @@ export interface Options extends ServerOptions {
export default class DevServer extends Server {
private devReady: Promise<void>
private setDevReady?: Function
private webpackWatcher?: Watchpack | null
private webpackWatcher?: any | null
private hotReloader?: HotReloader
private isCustomServer: boolean
protected sortedRoutes?: string[]
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9 changes: 1 addition & 8 deletions packages/next/taskfile.js
Original file line number Diff line number Diff line change
Expand Up @@ -591,13 +591,7 @@ export async function ncc_next_font(task, opts) {
}

// eslint-disable-next-line camelcase
externals['watchpack'] = 'next/dist/compiled/watchpack'
export async function ncc_watchpack(task, opts) {
await task
.source(relative(__dirname, require.resolve('watchpack')))
.ncc({ packageName: 'watchpack', externals })
.target('src/compiled/watchpack')
}
externals['watchpack'] = 'watchpack'

// eslint-disable-next-line camelcase
externals['jest-worker'] = 'next/dist/compiled/jest-worker'
Expand Down Expand Up @@ -2195,7 +2189,6 @@ export async function ncc(task, opts) {
.parallel(
[
'ncc_node_html_parser',
'ncc_watchpack',
'ncc_chalk',
'ncc_napirs_triples',
'ncc_p_limit',
Expand Down
4 changes: 4 additions & 0 deletions packages/next/types/misc.d.ts
Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,10 @@ declare module 'next/dist/compiled/babel/preset-env' {
const anyType: any
export default anyType
}
declare module 'watchpack' {
const anyType: any
export default anyType
}
declare module 'next/dist/compiled/babel/core' {
export * from '@babel/core'
}
Expand Down
9 changes: 4 additions & 5 deletions pnpm-lock.yaml

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