fix(nuxt): deduplicate app.head arrays (#27480)

packages/nuxt/src/core/nuxt.ts

@@ -7,6 +7,7 @@ import { resolvePath as _resolvePath } from 'mlly'
 import type { Nuxt, NuxtHooks, NuxtModule, NuxtOptions, RuntimeConfig } from 'nuxt/schema'
 import type { PackageJson } from 'pkg-types'
 import { readPackageJSON, resolvePackageJSON } from 'pkg-types'
+import { hash } from 'ohash'
 
 import escapeRE from 'escape-string-regexp'
 import fse from 'fs-extra'
@@ -583,6 +584,11 @@ export async function loadNuxt (opts: LoadNuxtOptions): Promise<Nuxt> {
   options.appDir = options.alias['#app'] = resolve(distDir, 'app')
   options._majorVersion = 3
 
+  // De-duplicate key arrays
+  for (const key in options.app.head || {}) {
+    options.app.head[key as 'link'] = deduplicateArray(options.app.head[key as 'link'])
+  }
+
   // Nuxt DevTools only works for Vite
   if (options.builder === '@nuxt/vite-builder') {
     const isDevToolsEnabled = typeof options.devtools === 'boolean'
@@ -668,3 +674,18 @@ async function checkDependencyVersion (name: string, nuxtVersion: string): Promi
 }
 
 const RESTART_RE = /^(?:app|error|app\.config)\.(?:js|ts|mjs|jsx|tsx|vue)$/i
+
+function deduplicateArray<T = unknown> (maybeArray: T): T {
+  if (!Array.isArray(maybeArray)) { return maybeArray }
+
+  const fresh = []
+  const hashes = new Set<string>()
+  for (const item of maybeArray) {
+    const _hash = hash(item)
+    if (!hashes.has(_hash)) {
+      hashes.add(_hash)
+      fresh.push(item)
+    }
+  }
+  return fresh as T
+}

test/basic.test.ts

@@ -64,6 +64,7 @@ describe('route rules', () => {
     expect(headHtml).toContain('<meta name="description" content="Nuxt Fixture">')
     expect(headHtml).toContain('<meta charset="utf-8">')
     expect(headHtml).toContain('<meta name="viewport" content="width=1024, initial-scale=1">')
+    expect(headHtml.match(/<meta name="viewport" content="width=1024, initial-scale=1">/g)).toHaveLength(1)
 
     const { script, attrs } = parseData(headHtml)
     expect(script.serverRendered).toEqual(false)

test/fixtures/basic/extends/bar/nuxt.config.ts

@@ -1,3 +1,11 @@
 export default defineNuxtConfig({
   modules: [undefined],
+  app: {
+    head: {
+      meta: [
+        { name: 'viewport', content: 'width=1024, initial-scale=1' },
+        { charset: 'utf-8' },
+      ],
+    },
+  },
 })