perf(nuxt): mark define functions as side-effect free at source (#21434)

.eslintrc

@@ -94,7 +94,10 @@
         "varsIgnorePattern": "^_",
         "ignoreRestSiblings": true
       }
-    ]
+    ],
+    "jsdoc/check-tag-names": ["error", {
+      "definedTags": ["__NO_SIDE_EFFECTS__"]
+    }]
   },
   "settings": {
     "jsdoc": {

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

@@ -22,6 +22,7 @@ export default defineComponent({
 
 const cache = new WeakMap()
 
+/*! @__NO_SIDE_EFFECTS__ */
 export function createClientOnly<T extends ComponentOptions> (component: T) {
   if (cache.has(component)) {
     return cache.get(component)

packages/nuxt/src/app/components/nuxt-link.ts

@@ -46,6 +46,7 @@ export type NuxtLinkProps = {
   ariaCurrentValue?: string
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 export function defineNuxtLink (options: NuxtLinkOptions) {
   const componentName = options.componentName || 'NuxtLink'
 

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

@@ -27,6 +27,7 @@ async function runLegacyAsyncData (res: Record<string, any> | Promise<Record<str
   }
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 export const defineNuxtComponent: typeof defineComponent =
   function defineNuxtComponent (...args: any[]): any {
     const [options, key] = args

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

@@ -42,7 +42,10 @@ export interface RouteMiddleware {
   (to: RouteLocationNormalized, from: RouteLocationNormalized): ReturnType<NavigationGuard>
 }
 
-export const defineNuxtRouteMiddleware = (middleware: RouteMiddleware) => middleware
+/*! @__NO_SIDE_EFFECTS__ */
+export function defineNuxtRouteMiddleware (middleware: RouteMiddleware) {
+  return middleware
+}
 
 export interface AddRouteMiddlewareOptions {
   global?: boolean

packages/nuxt/src/app/nuxt.ts

@@ -381,10 +381,12 @@ const orderMap: Record<NonNullable<ObjectPluginInput['enforce']>, number> = {
   post: 20
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 export function definePayloadPlugin<T extends Record<string, unknown>> (plugin: Plugin<T> | ObjectPluginInput<T>) {
   return defineNuxtPlugin(plugin, { order: -40 })
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 export function defineNuxtPlugin<T extends Record<string, unknown>> (plugin: Plugin<T> | ObjectPluginInput<T>, meta?: PluginMeta): Plugin<T> {
   if (typeof plugin === 'function') { return defineNuxtPlugin({ setup: plugin }, meta) }
 
@@ -433,6 +435,7 @@ export function callWithNuxt<T extends (...args: any[]) => any> (nuxt: NuxtApp |
   }
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 /**
  * Returns the current Nuxt instance.
  */
@@ -455,6 +458,7 @@ export function useNuxtApp (): NuxtApp {
   return nuxtAppInstance
 }
 
+/*! @__NO_SIDE_EFFECTS__ */
 export function useRuntimeConfig (): RuntimeConfig {
   return useNuxtApp().$config
 }

test/bundle.test.ts

@@ -45,7 +45,7 @@ describe.skipIf(isWindows || process.env.TEST_BUILDER === 'webpack' || process.e
 
   it('default server bundle size', async () => {
     stats.server = await analyzeSizes(['**/*.mjs', '!node_modules'], serverDir)
-    expect(roundToKilobytes(stats.server.totalBytes)).toMatchInlineSnapshot('"62.5k"')
+    expect(roundToKilobytes(stats.server.totalBytes)).toMatchInlineSnapshot('"62.6k"')
 
     const modules = await analyzeSizes('node_modules/**/*', serverDir)
     expect(roundToKilobytes(modules.totalBytes)).toMatchInlineSnapshot('"2284k"')