refactor(kit,nuxt,webpack): reduce reassignments (#30589)

packages/kit/src/build.ts

@@ -114,7 +114,7 @@ export function addWebpackPlugin (pluginOrGetter: WebpackPluginInstance | Webpac
     const method: 'push' | 'unshift' = options?.prepend ? 'unshift' : 'push'
     const plugin = typeof pluginOrGetter === 'function' ? pluginOrGetter() : pluginOrGetter
 
-    config.plugins = config.plugins || []
+    config.plugins ||= []
     config.plugins[method](...toArray(plugin))
   }, options)
 }
@@ -126,7 +126,7 @@ export function addRspackPlugin (pluginOrGetter: RspackPluginInstance | RspackPl
     const method: 'push' | 'unshift' = options?.prepend ? 'unshift' : 'push'
     const plugin = typeof pluginOrGetter === 'function' ? pluginOrGetter() : pluginOrGetter
 
-    config.plugins = config.plugins || []
+    config.plugins ||= []
     config.plugins[method](...toArray(plugin))
   }, options)
 }
@@ -139,7 +139,7 @@ export function addVitePlugin (pluginOrGetter: VitePlugin | VitePlugin[] | (() =
     const method: 'push' | 'unshift' = options?.prepend ? 'unshift' : 'push'
     const plugin = typeof pluginOrGetter === 'function' ? pluginOrGetter() : pluginOrGetter
 
-    config.plugins = config.plugins || []
+    config.plugins ||= []
     config.plugins[method](...toArray(plugin))
   }, options)
 }

packages/kit/src/components.ts

@@ -11,7 +11,7 @@ import { MODE_RE } from './utils'
 export async function addComponentsDir (dir: ComponentsDir, opts: { prepend?: boolean } = {}) {
   const nuxt = useNuxt()
   await assertNuxtCompatibility({ nuxt: '>=2.13' }, nuxt)
-  nuxt.options.components = nuxt.options.components || []
+  nuxt.options.components ||= []
   dir.priority ||= 0
   nuxt.hook('components:dirs', (dirs) => { dirs[opts.prepend ? 'unshift' : 'push'](dir) })
 }
@@ -26,7 +26,7 @@ export type AddComponentOptions = { name: string, filePath: string } & Partial<E
 export async function addComponent (opts: AddComponentOptions) {
   const nuxt = useNuxt()
   await assertNuxtCompatibility({ nuxt: '>=2.13' }, nuxt)
-  nuxt.options.components = nuxt.options.components || []
+  nuxt.options.components ||= []
 
   if (!opts.mode) {
     const [, mode = 'all'] = opts.filePath.match(MODE_RE) || []

packages/kit/src/loader/config.ts

@@ -58,7 +58,7 @@ export async function loadNuxtConfig (opts: LoadNuxtConfigOptions): Promise<Nuxt
   const processedLayers = new Set<string>()
   for (const layer of layers) {
     // Resolve `rootDir` & `srcDir` of layers
-    layer.config = layer.config || {}
+    layer.config ||= {}
     layer.config.rootDir = layer.config.rootDir ?? layer.cwd!
 
     // Only process/resolve layers once

packages/kit/src/loader/nuxt.ts

@@ -16,7 +16,7 @@ export interface LoadNuxtOptions extends LoadNuxtConfigOptions {
 export async function loadNuxt (opts: LoadNuxtOptions): Promise<Nuxt> {
   // Backward compatibility
   opts.cwd = resolve(opts.cwd || (opts as any).rootDir /* backwards compat */ || '.')
-  opts.overrides = opts.overrides || (opts as any).config as NuxtConfig /* backwards compat */ || {}
+  opts.overrides ||= (opts as any).config as NuxtConfig /* backwards compat */ || {}
 
   // Apply dev as config override
   opts.overrides.dev = !!opts.dev

packages/kit/src/module/define.ts

@@ -87,7 +87,7 @@ function _defineNuxtModule<
     // Avoid duplicate installs
     const uniqueKey = module.meta.name || module.meta.configKey
     if (uniqueKey) {
-      nuxt.options._requiredModules = nuxt.options._requiredModules || {}
+      nuxt.options._requiredModules ||= {}
       if (nuxt.options._requiredModules[uniqueKey]) {
         return false
       }

packages/kit/src/module/install.ts

@@ -44,7 +44,7 @@ export async function installModule<
     }
   }
 
-  nuxt.options._installedModules = nuxt.options._installedModules || []
+  nuxt.options._installedModules ||= []
   const entryPath = typeof moduleToInstall === 'string' ? resolveAlias(moduleToInstall) : undefined
 
   if (typeof moduleToInstall === 'string' && entryPath !== moduleToInstall) {

packages/kit/src/nitro.ts

@@ -40,7 +40,7 @@ export function addDevServerHandler (handler: NitroDevEventHandler) {
  */
 export function addServerPlugin (plugin: string) {
   const nuxt = useNuxt()
-  nuxt.options.nitro.plugins = nuxt.options.nitro.plugins || []
+  nuxt.options.nitro.plugins ||= []
   nuxt.options.nitro.plugins.push(normalize(plugin))
 }
 
@@ -89,8 +89,8 @@ export function useNitro (): Nitro {
 export function addServerImports (imports: Import[]) {
   const nuxt = useNuxt()
   nuxt.hook('nitro:config', (config) => {
-    config.imports = config.imports || {}
+    config.imports ||= {}
-    config.imports.imports = config.imports.imports || []
+    config.imports.imports ||= []
     config.imports.imports.push(...imports)
   })
 }
@@ -102,8 +102,8 @@ export function addServerImportsDir (dirs: string | string[], opts: { prepend?:
   const nuxt = useNuxt()
   const _dirs = toArray(dirs)
   nuxt.hook('nitro:config', (config) => {
-    config.imports = config.imports || {}
+    config.imports ||= {}
-    config.imports.dirs = config.imports.dirs || []
+    config.imports.dirs ||= []
     config.imports.dirs[opts.prepend ? 'unshift' : 'push'](..._dirs)
   })
 }
@@ -115,7 +115,7 @@ export function addServerImportsDir (dirs: string | string[], opts: { prepend?:
 export function addServerScanDir (dirs: string | string[], opts: { prepend?: boolean } = {}) {
   const nuxt = useNuxt()
   nuxt.hook('nitro:config', (config) => {
-    config.scanDirs = config.scanDirs || []
+    config.scanDirs ||= []
 
     for (const dir of toArray(dirs)) {
       config.scanDirs[opts.prepend ? 'unshift' : 'push'](dir)

packages/kit/src/pages.ts

@@ -20,9 +20,7 @@ export interface ExtendRouteRulesOptions {
 export function extendRouteRules (route: string, rule: NitroRouteConfig, options: ExtendRouteRulesOptions = {}) {
   const nuxt = useNuxt()
   for (const opts of [nuxt.options, nuxt.options.nitro]) {
-    if (!opts.routeRules) {
+    opts.routeRules ||= {}
-      opts.routeRules = {}
-    }
     opts.routeRules[route] = options.override
       ? defu(rule, opts.routeRules[route])
       : defu(opts.routeRules[route], rule)

packages/kit/src/plugin.ts

@@ -5,10 +5,10 @@ import { normalize } from 'pathe'
 import type { NuxtPlugin, NuxtPluginTemplate } from '@nuxt/schema'
 import { resolvePathSync } from 'mlly'
 import { isWindows } from 'std-env'
+import { MODE_RE, filterInPlace } from './utils'
 import { tryUseNuxt, useNuxt } from './context'
 import { addTemplate } from './template'
 import { resolveAlias } from './resolve'
-import { MODE_RE } from './utils'
 
 /**
  * Normalize a nuxt plugin object
@@ -82,7 +82,7 @@ export function addPlugin (_plugin: NuxtPlugin | string, opts: AddPluginOptions
   const plugin = normalizePlugin(_plugin)
 
   // Remove any existing plugin with the same src
-  nuxt.options.plugins = nuxt.options.plugins.filter(p => normalizePlugin(p).src !== plugin.src)
+  filterInPlace(nuxt.options.plugins, p => normalizePlugin(p).src !== plugin.src)
 
   // Prepend to array by default to be before user provided plugins since is usually used by modules
   nuxt.options.plugins[opts.append ? 'push' : 'unshift'](plugin)

packages/kit/src/template.ts

@@ -8,6 +8,7 @@ import type { TSConfig } from 'pkg-types'
 import { gte } from 'semver'
 import { readPackageJSON } from 'pkg-types'
 
+import { filterInPlace } from './utils'
 import { tryResolveModule } from './internal/esm'
 import { getDirectory } from './module/install'
 import { tryUseNuxt, useNuxt } from './context'
@@ -23,7 +24,7 @@ export function addTemplate<T> (_template: NuxtTemplate<T> | string) {
   const template = normalizeTemplate(_template)
 
   // Remove any existing template with the same destination path
-  nuxt.options.build.templates = nuxt.options.build.templates.filter(p => normalizeTemplate(p).dst !== template.dst)
+  filterInPlace(nuxt.options.build.templates, p => normalizeTemplate(p).dst !== template.dst)
 
   // Add to templates array
   nuxt.options.build.templates.push(template)
@@ -229,9 +230,9 @@ export async function _generateTypes (nuxt: Nuxt) {
     ? resolve(nuxt.options.buildDir, tsConfig.compilerOptions!.baseUrl)
     : nuxt.options.buildDir
 
-  tsConfig.compilerOptions = tsConfig.compilerOptions || {}
+  tsConfig.compilerOptions ||= {}
-  tsConfig.compilerOptions.paths = tsConfig.compilerOptions.paths || {}
+  tsConfig.compilerOptions.paths ||= {}
-  tsConfig.include = tsConfig.include || []
+  tsConfig.include ||= []
 
   for (const alias in aliases) {
     if (excludedAlias.some(re => re.test(alias))) {

packages/kit/src/utils.ts

@@ -3,4 +3,19 @@ export function toArray<T> (value: T | T[]): T[] {
   return Array.isArray(value) ? value : [value]
 }
 
+/**
+ * Filter out items from an array in place. This function mutates the array.
+ * `predicate` get through the array from the end to the start for performance.
+ *
+ * This function should be faster than `Array.prototype.filter` on large arrays.
+ */
+export function filterInPlace<T> (array: T[], predicate: (item: T, index: number, arr: T[]) => unknown) {
+  for (let i = array.length; i--; i >= 0) {
+    if (!predicate(array[i]!, i, array)) {
+      array.splice(i, 1)
+    }
+  }
+  return array
+}
+
 export const MODE_RE = /\.(server|client)(\.\w+)*$/

packages/nuxt/src/app/components/client-only.ts

@@ -95,7 +95,7 @@ export function createClientOnly<T extends ComponentOptions> (component: T) {
     if (isPromise(setupState)) {
       return Promise.resolve(setupState).then((setupState) => {
         if (typeof setupState !== 'function') {
-          setupState = setupState || {}
+          setupState ||= {}
           setupState.mounted$ = mounted$
           return setupState
         }

packages/nuxt/src/app/composables/once.ts

@@ -37,7 +37,7 @@ export async function callOnce (...args: any): Promise<void> {
     return
   }
 
-  nuxtApp._once = nuxtApp._once || {}
+  nuxtApp._once ||= {}
   nuxtApp._once[_key] = nuxtApp._once[_key] || fn() || true
   await nuxtApp._once[_key]
   nuxtApp.payload.once.add(_key)

packages/nuxt/src/components/module.ts

@@ -250,7 +250,7 @@ export default defineNuxtModule<ComponentsOptions>({
 
       // TODO: refactor this
       nuxt.hook('vite:extendConfig', (config, { isClient }) => {
-        config.plugins = config.plugins || []
+        config.plugins ||= []
 
         if (isClient && selectiveClient) {
           writeFileSync(join(nuxt.options.buildDir, 'components-chunk.mjs'), 'export const paths = {}')
@@ -275,7 +275,7 @@ export default defineNuxtModule<ComponentsOptions>({
         nuxt.hook(key, (configs) => {
           configs.forEach((config) => {
             const mode = config.name === 'client' ? 'client' : 'server'
-            config.plugins = config.plugins || []
+            config.plugins ||= []
 
             if (mode !== 'server') {
               writeFileSync(join(nuxt.options.buildDir, 'components-chunk.mjs'), 'export const paths = {}')

packages/nuxt/src/core/nitro.ts

@@ -239,7 +239,11 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
 
   // Resolve user-provided paths
   nitroConfig.srcDir = resolve(nuxt.options.rootDir, nuxt.options.srcDir, nitroConfig.srcDir!)
-  nitroConfig.ignore = [...(nitroConfig.ignore || []), ...resolveIgnorePatterns(nitroConfig.srcDir), `!${join(nuxt.options.buildDir, 'dist/client', nuxt.options.app.buildAssetsDir, '**/*')}`]
+  nitroConfig.ignore ||= []
+  nitroConfig.ignore.push(
+    ...resolveIgnorePatterns(nitroConfig.srcDir),
+    `!${join(nuxt.options.buildDir, 'dist/client', nuxt.options.app.buildAssetsDir, '**/*')}`,
+  )
 
   // Resolve aliases in user-provided input - so `~/server/test` will work
   nitroConfig.plugins = nitroConfig.plugins?.map(plugin => plugin ? resolveAlias(plugin, nuxt.options.alias) : plugin)
@@ -411,14 +415,16 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
   const basePath = nitroConfig.typescript!.tsConfig!.compilerOptions?.baseUrl ? resolve(nuxt.options.buildDir, nitroConfig.typescript!.tsConfig!.compilerOptions?.baseUrl) : nuxt.options.buildDir
   const aliases = nitroConfig.alias!
   const tsConfig = nitroConfig.typescript!.tsConfig!
-  tsConfig.compilerOptions = tsConfig.compilerOptions || {}
+  tsConfig.compilerOptions ||= {}
-  tsConfig.compilerOptions.paths = tsConfig.compilerOptions.paths || {}
+  tsConfig.compilerOptions.paths ||= {}
   for (const _alias in aliases) {
     const alias = _alias as keyof typeof aliases
     if (excludedAlias.some(pattern => typeof pattern === 'string' ? alias === pattern : pattern.test(alias))) {
       continue
     }
-    if (alias in tsConfig.compilerOptions.paths) { continue }
+    if (alias in tsConfig.compilerOptions.paths) {
+      continue
+    }
 
     const absolutePath = resolve(basePath, aliases[alias]!)
     const stats = await fsp.stat(absolutePath).catch(() => null /* file does not exist */)
@@ -532,7 +538,7 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
       await writeTypes(nitro)
     }
     // Exclude nitro output dir from typescript
-    opts.tsConfig.exclude = opts.tsConfig.exclude || []
+    opts.tsConfig.exclude ||= []
     opts.tsConfig.exclude.push(relative(nuxt.options.buildDir, resolve(nuxt.options.rootDir, nitro.options.output.dir)))
     opts.references.push({ path: resolve(nuxt.options.buildDir, 'types/nitro.d.ts') })
   })

packages/nuxt/src/core/runtime/nitro/no-ssr.ts

@@ -2,7 +2,7 @@ import { defineEventHandler, getRequestHeader } from 'h3'
 
 export default defineEventHandler((event) => {
   if (getRequestHeader(event, 'x-nuxt-no-ssr')) {
-    event.context.nuxt = event.context.nuxt || {}
+    event.context.nuxt ||= {}
     event.context.nuxt.noSSR = true
   }
 })

packages/nuxt/src/core/runtime/nitro/renderer.ts

@@ -488,8 +488,8 @@ export default defineRenderHandler(async (event): Promise<Partial<RenderResponse
     }
 
     // TODO: remove for v4
-    islandHead.link = islandHead.link || []
+    islandHead.link ||= []
-    islandHead.style = islandHead.style || []
+    islandHead.style ||= []
 
     const islandResponse: NuxtIslandResponse = {
       id: islandContext.id,

packages/nuxt/src/pages/module.ts

@@ -530,8 +530,8 @@ export default defineNuxtModule({
       getContents: () => 'export { START_LOCATION, useRoute } from \'vue-router\'',
     })
 
-    nuxt.options.vite.resolve = nuxt.options.vite.resolve || {}
+    nuxt.options.vite.resolve ||= {}
-    nuxt.options.vite.resolve.dedupe = nuxt.options.vite.resolve.dedupe || []
+    nuxt.options.vite.resolve.dedupe ||= []
     nuxt.options.vite.resolve.dedupe.push('vue-router')
 
     // Add router options template

packages/webpack/src/configs/client.ts

@@ -56,7 +56,7 @@ function clientNodeCompat (ctx: WebpackConfigContext) {
   }
   ctx.config.plugins!.push(new webpack.DefinePlugin({ global: 'globalThis' }))
 
-  ctx.config.resolve = ctx.config.resolve || {}
+  ctx.config.resolve ||= {}
   ctx.config.resolve.fallback = {
     ...env(nodeless).alias,
     ...ctx.config.resolve.fallback,
@@ -92,7 +92,7 @@ function clientHMR (ctx: WebpackConfigContext) {
     `webpack-hot-middleware/client?${hotMiddlewareClientOptionsStr}`,
   )
 
-  ctx.config.plugins = ctx.config.plugins || []
+  ctx.config.plugins ||= []
   ctx.config.plugins.push(new webpack.HotModuleReplacementPlugin())
 }
 

packages/webpack/src/configs/server.ts

@@ -85,7 +85,7 @@ function serverStandalone (ctx: WebpackConfigContext) {
 }
 
 function serverPlugins (ctx: WebpackConfigContext) {
-  ctx.config.plugins = ctx.config.plugins || []
+  ctx.config.plugins ||= []
 
   // Server polyfills
   if (ctx.userConfig.serverURLPolyfill) {

packages/webpack/src/presets/base.ts

@@ -50,7 +50,7 @@ function baseConfig (ctx: WebpackConfigContext) {
 }
 
 function basePlugins (ctx: WebpackConfigContext) {
-  ctx.config.plugins = ctx.config.plugins || []
+  ctx.config.plugins ||= []
 
   // Add timefix-plugin before other plugins
   if (ctx.options.dev) {