perf(vite): remove duplicate css links from rendered page when inlined (#7264)

packages/vite/src/client.ts

@@ -14,7 +14,6 @@ import type { OutputOptions } from 'rollup'
 import { cacheDirPlugin } from './plugins/cache-dir'
 import { wpfs } from './utils/wpfs'
 import type { ViteBuildContext, ViteOptions } from './vite'
-import { writeManifest } from './manifest'
 import { devStyleSSRPlugin } from './plugins/dev-ssr-css'
 import { viteNodePlugin } from './vite-node'
 
@@ -140,6 +139,4 @@ export async function buildClient (ctx: ViteBuildContext) {
     await ctx.nuxt.callHook('build:resources', wpfs)
     logger.info(`Client built in ${Date.now() - start}ms`)
   }
-
-  await writeManifest(ctx)
 }

packages/vite/src/plugins/ssr-styles.ts

@@ -9,11 +9,12 @@ import { isCSS } from '../utils'
 
 interface SSRStylePluginOptions {
   srcDir: string
+  chunksWithInlinedCSS: Set<string>
   shouldInline?: (id?: string) => boolean
 }
 
 export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
-  const cssMap: Record<string, string[]> = {}
+  const cssMap: Record<string, { files: string[], inBundle: boolean }> = {}
   const idRefMap: Record<string, string> = {}
   const globalStyles = new Set<string>()
 
@@ -24,7 +25,9 @@ export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
     generateBundle (outputOptions) {
       const emitted: Record<string, string> = {}
       for (const file in cssMap) {
-        if (!cssMap[file].length) { continue }
+        const { files, inBundle } = cssMap[file]
+        // File has been tree-shaken out of build (or there are no styles to inline)
+        if (!files.length || !inBundle) { continue }
 
         const base = typeof outputOptions.assetFileNames === 'string'
           ? outputOptions.assetFileNames
@@ -38,14 +41,19 @@ export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
           type: 'asset',
           name: `${filename(file)}-styles.mjs`,
           source: [
-            ...cssMap[file].map((css, i) => `import style_${i} from './${relative(dirname(base), this.getFileName(css))}';`),
-            `export default [${cssMap[file].map((_, i) => `style_${i}`).join(', ')}]`
+            ...files.map((css, i) => `import style_${i} from './${relative(dirname(base), this.getFileName(css))}';`),
+            `export default [${files.map((_, i) => `style_${i}`).join(', ')}]`
           ].join('\n')
         })
       }
 
       const globalStylesArray = Array.from(globalStyles).map(css => idRefMap[css] && this.getFileName(idRefMap[css])).filter(Boolean)
 
+      for (const key in emitted) {
+        // Track the chunks we are inlining CSS for so we can omit including links to the .css files
+        options.chunksWithInlinedCSS.add(key)
+      }
+
       this.emitFile({
         type: 'asset',
         fileName: 'styles.mjs',
@@ -61,11 +69,21 @@ export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
       })
     },
     renderChunk (_code, chunk) {
-      if (!chunk.isEntry) { return null }
-      // Entry
-      for (const mod in chunk.modules) {
-        if (isCSS(mod) && !mod.includes('&used')) {
-          globalStyles.add(relativeToSrcDir(mod))
+      if (!chunk.facadeModuleId) { return null }
+      const id = relativeToSrcDir(chunk.facadeModuleId)
+      for (const file in chunk.modules) {
+        const relativePath = relativeToSrcDir(file)
+        if (relativePath in cssMap) {
+          cssMap[relativePath].inBundle = cssMap[relativePath].inBundle ?? !!id
+        }
+      }
+
+      if (chunk.isEntry) {
+        // Entry
+        for (const mod in chunk.modules) {
+          if (isCSS(mod) && !mod.includes('&used')) {
+            globalStyles.add(relativeToSrcDir(mod))
+          }
         }
       }
       return null
@@ -77,7 +95,7 @@ export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
       if (options.shouldInline && !options.shouldInline(id)) { return }
 
       const relativeId = relativeToSrcDir(id)
-      cssMap[relativeId] = cssMap[relativeId] || []
+      cssMap[relativeId] = cssMap[relativeId] || { files: [] }
 
       let styleCtr = 0
       for (const i of findStaticImports(code)) {
@@ -94,7 +112,7 @@ export function ssrStylesPlugin (options: SSRStylePluginOptions): Plugin {
         })
 
         idRefMap[relativeToSrcDir(resolved.id)] = ref
-        cssMap[relativeId].push(ref)
+        cssMap[relativeId].files.push(ref)
       }
     }
   }

packages/vite/src/server.ts

@@ -10,6 +10,7 @@ import { wpfs } from './utils/wpfs'
 import { cacheDirPlugin } from './plugins/cache-dir'
 import { initViteNodeServer } from './vite-node'
 import { ssrStylesPlugin } from './plugins/ssr-styles'
+import { writeManifest } from './manifest'
 
 export async function buildServer (ctx: ViteBuildContext) {
   const useAsyncEntry = ctx.nuxt.options.experimental.asyncEntry ||
@@ -113,12 +114,35 @@ export async function buildServer (ctx: ViteBuildContext) {
   } as ViteOptions)
 
   if (ctx.nuxt.options.experimental.inlineSSRStyles) {
+    const chunksWithInlinedCSS = new Set<string>()
     serverConfig.plugins!.push(ssrStylesPlugin({
       srcDir: ctx.nuxt.options.srcDir,
+      chunksWithInlinedCSS,
       shouldInline: typeof ctx.nuxt.options.experimental.inlineSSRStyles === 'function'
         ? ctx.nuxt.options.experimental.inlineSSRStyles
         : undefined
     }))
+
+    // Remove CSS entries for files that will have inlined styles
+    ctx.nuxt.hook('build:manifest', (manifest) => {
+      for (const key in manifest) {
+        const entry = manifest[key]
+        const shouldRemoveCSS = chunksWithInlinedCSS.has(key)
+        if (shouldRemoveCSS) {
+          entry.css = []
+        }
+        // Add entry CSS as prefetch (non-blocking)
+        if (entry.isEntry) {
+          manifest[key + '-css'] = {
+            file: '',
+            css: entry.css
+          }
+          entry.css = []
+          entry.dynamicImports = entry.dynamicImports || []
+          entry.dynamicImports.push(key + '-css')
+        }
+      }
+    })
   }
 
   // Add type-checking
@@ -140,6 +164,8 @@ export async function buildServer (ctx: ViteBuildContext) {
     const start = Date.now()
     logger.info('Building server...')
     await vite.build(serverConfig)
+    // Write production client manifest
+    await writeManifest(ctx)
     await onBuild()
     logger.success(`Server built in ${Date.now() - start}ms`)
     return
@@ -150,6 +176,9 @@ export async function buildServer (ctx: ViteBuildContext) {
     return
   }
 
+  // Write dev client manifest
+  await writeManifest(ctx)
+
   // Start development server
   const viteServer = await vite.createServer(serverConfig)
   ctx.ssrServer = viteServer

test/basic.test.ts

@@ -2,7 +2,7 @@ import { fileURLToPath } from 'node:url'
 import { describe, expect, it } from 'vitest'
 import { joinURL } from 'ufo'
 // import { isWindows } from 'std-env'
-import { setup, fetch, $fetch, startServer } from '@nuxt/test-utils'
+import { setup, fetch, $fetch, startServer, createPage } from '@nuxt/test-utils'
 // eslint-disable-next-line import/order
 import { expectNoClientErrors, renderPage } from './utils'
 
@@ -384,8 +384,23 @@ if (!process.env.NUXT_TEST_DEV && !process.env.TEST_WITH_WEBPACK) {
         expect(html).toContain(style)
       }
     })
-    it.todo('does not render style hints for inlined styles')
-    it.todo('renders client-only styles?', async () => {
+
+    it('only renders prefetch for entry styles', async () => {
+      const html: string = await $fetch('/styles')
+      expect(html.match(/<link [^>]*href="[^"]*\.css">/)?.map(m => m.replace(/\.[^.]*\.css/, '.css'))).toMatchInlineSnapshot(`
+        [
+          "<link rel=\\"prefetch stylesheet\\" href=\\"/_nuxt/entry.css\\">",
+        ]
+      `)
+    })
+
+    it('still downloads client-only styles', async () => {
+      const page = await createPage('/styles')
+      await page.waitForLoadState('networkidle')
+      expect(await page.$eval('.client-only-css', e => getComputedStyle(e).color)).toBe('rgb(50, 50, 50)')
+    })
+
+    it.todo('renders client-only styles only', async () => {
       const html = await $fetch('/styles')
       expect(html).toContain('{--client-only:"client-only"}')
     })

test/fixtures/basic/components/ClientOnlyScript.client.vue

@@ -11,7 +11,9 @@ export default defineNuxtComponent({
 
 <template>
   <div>
-    <div>client only script component {{ foo }}</div>
+    <div class="client-only-css">
+      client only script component {{ foo }}
+    </div>
     <slot name="test" />
   </div>
 </template>
@@ -21,3 +23,9 @@ export default defineNuxtComponent({
     --client-only: 'client-only';
   }
 </style>
+
+<style scoped>
+  .client-only-css {
+    color: rgb(50, 50, 50);
+  }
+</style>

test/fixtures/basic/nuxt.config.ts

@@ -36,6 +36,7 @@ export default defineNuxtConfig({
     }
   },
   experimental: {
+    inlineSSRStyles: id => !id.includes('assets.vue'),
     reactivityTransform: true,
     treeshakeClientOnly: true
   },