fix(vue): missing unhead context (#3589)

Co-authored-by: Benjamin Canac <canacb1@gmail.com>

src/runtime/plugins/colors.ts

@@ -2,6 +2,7 @@ import { computed } from 'vue'
 import { defineNuxtPlugin, useAppConfig, useNuxtApp, useHead } from '#imports'
 // FIXME: https://github.com/nuxt/module-builder/issues/141#issuecomment-2078248248
 import type {} from '#app'
+import type { UseHeadInput } from '@unhead/vue/types'
 
 export default defineNuxtPlugin(() => {
   const appConfig = useAppConfig()
@@ -33,12 +34,11 @@ export default defineNuxtPlugin(() => {
   })
 
   // Head
-  const headData: any = {
+  const headData: UseHeadInput = {
     style: [{
       innerHTML: () => root.value,
-      tagPriority: -2,
+      tagPriority: 'critical',
-      id: 'nuxt-ui-colors',
+      id: 'nuxt-ui-colors'
-      type: 'text/css'
     }]
   }
 
@@ -55,7 +55,5 @@ export default defineNuxtPlugin(() => {
     }]
   }
 
-  if (!nuxtApp.isVue) {
+  useHead(headData)
-    useHead(headData)
-  }
 })

src/runtime/vue/plugins/head.ts

@@ -3,6 +3,11 @@ import type { Plugin } from 'vue'
 
 export default {
   install(app) {
+    // check for existing head instance to avoid replacement
+    // bit hacky but we can't use injectHead() here
+    if (app._context.provides.usehead) {
+      return
+    }
     const head = createHead()
     app.use(head)
   }

src/runtime/vue/stubs.ts

@@ -61,7 +61,6 @@ export const useState = <T>(key: string, init: () => T): Ref<T> => {
 export function useNuxtApp() {
   return {
     isHydrating: true,
-    isVue: true,
     payload: { serverRendered: false }
   }
 }
@@ -69,7 +68,7 @@ export function useNuxtApp() {
 export function defineNuxtPlugin(plugin: (nuxtApp: NuxtApp) => void) {
   return {
     install(app) {
-      plugin({ vueApp: app } as NuxtApp)
+      app.runWithContext(() => plugin({ vueApp: app } as NuxtApp))
     }
   } satisfies VuePlugin
 }