fix: Change union rule to array type meta #2614

Author: taichunmin

Diff for: packages/@vuepress/core/lib/client/root-mixins/updateMeta.js

@@ -1,5 +1,20 @@
 import unionBy from 'lodash/unionBy'
 
+// @see https://ogp.me/
+const META_TYPE_ARRAY = [
+  'article:author',
+  'article:tag',
+  'book:author',
+  'book:tag',
+  'music:album',
+  'music:musician',
+  'og:locale:alternate',
+  'video:actor',
+  'video:director',
+  'video:tag',
+  'video:writer'
+]
+
 export default {
   // created will be called on both client and ssr
   created () {
@@ -86,7 +101,11 @@ function updateMetaTags (newMetaTags, currentMetaTags) {
  */
 function metaIdentifier (tag) {
   for (const item of ['name', 'property', 'itemprop']) {
-    if (tag.hasOwnProperty(item)) return tag[item] + item
+    if (tag.hasOwnProperty(item)) {
+      const key = tag[item]
+      const isTypeArray = tag.hasOwnProperty('content') && ~META_TYPE_ARRAY.indexOf(key)
+      return key + item + (isTypeArray ? tag.content : '')
+    }
   }
   return JSON.stringify(tag)
 }