change head compute time

Author: leaves4j

src/plugins/server.js

@@ -26,10 +26,9 @@ const SSRServerPlugin = {
         if (this.$options.router !== undefined) {
           this.$options.router.push(context.url);
         }
-        const head = typeof this.$options.head === 'function' ?
-          this.$options.head.call(this) :
-          this.$options.head || {};
-        this.$options.head = head;
+        this.$options.$getHead = typeof this.$options.head === 'function' ?
+          this.$options.head.bind(this) :
+          () => (this.$options.head || {});
       },
     });
   },

src/renderer/renderer.js

@@ -144,7 +144,7 @@ class Renderer extends EventEmitter implements IRenderer {
 
       if (isPure) return bodyStream;
 
-      const head = component.$options.head;
+      const head = component.$options.$getHead();
       const mergedHead = VueHead.headMerge(head, this.options.head);
       const template = Renderer.getTemplateHtml(mergedHead, context.state, this.options.global);
       const transform = new StreamTransform(template.head, template.tail);