feat: allow accessing meta properties in onGlobalSetup

closes #305

docs/content/en/helpers/useMeta.md

@@ -6,7 +6,7 @@ fullscreen: True
 position: 18
 ---
 
-You can interact directly with [head properties](https://nuxtjs.org/api/pages-head/) in `setup` by means of the `useMeta()` helper.
+You can interact directly with [head properties](https://nuxtjs.org/api/pages-head/) in `setup` (and within the `onGlobalSetup` method) by means of the `useMeta()` helper.
 
 ```ts
 import { defineComponent, useMeta, computed, ref } from '@nuxtjs/composition-api'

src/hooks.ts

@@ -1,5 +1,6 @@
 import type { Plugin } from '@nuxt/types'
 import type { SetupContext } from '@vue/composition-api'
+import { getHeadOptions } from './meta'
 
 import { reqRefs } from './req-ref'
 import { setSSRContext } from './ssr-ref'
@@ -39,6 +40,10 @@ export const globalPlugin: Plugin = context => {
   if (process.server) {
     reqRefs.forEach(reset => reset())
   }
+
+  const { head } = context.app
+  Object.assign(context.app, getHeadOptions({ head: head as any }))
+
   context.app.setup = function (...args) {
     let result = {}
     if (setup instanceof Function) {

test/fixture/layouts/default.vue

@@ -22,10 +22,7 @@ export default defineComponent({
   setup() {
     const { route } = useContext()
 
-    const { title } = useMeta()
-    title.value = 'My fixture'
-
-    return { route, title }
+    return { route }
   },
 })
 </script>

test/fixture/plugins/global.js

@@ -1,5 +1,6 @@
 import {
   onGlobalSetup,
+  useMeta,
   provide,
   ref,
   ssrRef,
@@ -16,6 +17,9 @@ export default () => {
   onGlobalSetup(() => {
     const { $config } = useContext()
 
+    const { title } = useMeta()
+    title.value = 'My fixture'
+
     ran.value++
     if (process.server) ranSsr.value++