1 files changed, 59 insertions, 0 deletions
diff --git a/node_modules/vuepress/lib/app/root-mixins/updateMeta.js b/node_modules/vuepress/lib/app/root-mixins/updateMeta.js
new file mode 100644
index 00000000..ff2703ac
--- /dev/null
+++ b/node_modules/vuepress/lib/app/root-mixins/updateMeta.js
@@ -0,0 +1,59 @@
+export default {
+  created () {
+    if (this.$ssrContext) {
+      this.$ssrContext.title = this.$title
+      this.$ssrContext.lang = this.$lang
+      this.$ssrContext.description = this.$page.description || this.$description
+    }
+  },
+
+  mounted () {
+    // update title / meta tags
+    this.currentMetaTags = new Set()
+
+    const updateMeta = () => {
+      document.title = this.$title
+      document.documentElement.lang = this.$lang
+      const userMeta = this.$page.frontmatter.meta || []
+      const meta = userMeta.slice(0)
+      const useGlobalDescription = userMeta.filter(m => m.name === 'description').length === 0
+
+      // #665 Avoid duplicate description meta at runtime.
+      if (useGlobalDescription) {
+        meta.push({ name: 'description', content: this.$description })
+      }
+
+      // Including description meta coming from SSR.
+      const descriptionMetas = document.querySelectorAll('meta[name="description"]')
+      if (descriptionMetas.length) {
+        descriptionMetas.forEach(m => this.currentMetaTags.add(m))
+      }
+
+      this.currentMetaTags = new Set(updateMetaTags(meta, this.currentMetaTags))
+    }
+    this.$watch('$page', updateMeta)
+    updateMeta()
+  },
+
+  beforeDestroy () {
+    updateMetaTags(null, this.currentMetaTags)
+  }
+}
+
+function updateMetaTags (meta, current) {
+  if (current) {
+    [...current].forEach(c => {
+      document.head.removeChild(c)
+    })
+  }
+  if (meta) {
+    return meta.map(m => {
+      const tag = document.createElement('meta')
+      Object.keys(m).forEach(key => {
+        tag.setAttribute(key, m[key])
+      })
+      document.head.appendChild(tag)
+      return tag
+    })
+  }
+}