From 34ea5ae2f294c19bc84fa92c0521568f5d024d55 Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@roe.dev>
Date: Fri, 7 Jun 2024 15:24:56 +0100
Subject: [PATCH] fix(nuxt): deduplicate `app.head` arrays (#27480)

---
 packages/nuxt/src/core/nuxt.ts                | 21 +++++++++++++++++++
 test/basic.test.ts                            |  1 +
 .../fixtures/basic/extends/bar/nuxt.config.ts |  8 +++++++
 3 files changed, 30 insertions(+)

diff --git a/packages/nuxt/src/core/nuxt.ts b/packages/nuxt/src/core/nuxt.ts
index 228eaa423a..8b5d389967 100644
--- a/packages/nuxt/src/core/nuxt.ts
+++ b/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
+}
diff --git a/test/basic.test.ts b/test/basic.test.ts
index da188dfc68..1e4db83c89 100644
--- a/test/basic.test.ts
+++ b/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)
diff --git a/test/fixtures/basic/extends/bar/nuxt.config.ts b/test/fixtures/basic/extends/bar/nuxt.config.ts
index 680205b4f0..f32e267e8f 100644
--- a/test/fixtures/basic/extends/bar/nuxt.config.ts
+++ b/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' },
+      ],
+    },
+  },
 })