fix(v-pre): do not alter attributes

close vuejs#10087

Author: xmakina

src/platforms/web/runtime/modules/attrs.js

@@ -39,7 +39,7 @@ function updateAttrs (oldVnode: VNodeWithData, vnode: VNodeWithData) {
     cur = attrs[key]
     old = oldAttrs[key]
     if (old !== cur) {
-      setAttr(elm, key, cur)
+      setAttr(elm, key, cur, vnode.data.pre)
     }
   }
   // #4391: in IE9, setting type can reset value for input[type=radio]
@@ -59,9 +59,11 @@ function updateAttrs (oldVnode: VNodeWithData, vnode: VNodeWithData) {
   }
 }
 
-function setAttr (el: Element, key: string, value: any) {
+function setAttr (el: Element, key: string, value: any, isInPre: any) {
   if (el.tagName.indexOf('-') > -1) {
     baseSetAttr(el, key, value)
+  } else if(isInPre) {
+    baseSetAttr(el, key, value)
   } else if (isBooleanAttr(key)) {
     // set attribute for blank value
     // e.g. <option disabled>Select one</option>

test/unit/features/directives/pre.spec.js

@@ -42,4 +42,15 @@ describe('Directive v-pre', function () {
     vm.$mount()
     expect(vm.$el.firstChild.tagName).toBe('VTEST')
   })
+
+  // #10087
+  it('should not compile attributes', function () {
+    Vue.component('vtest', { template: ` <div>Hello World</div>` })
+    const vm = new Vue({
+      template: '<div v-pre><vtest open="hello"></vtest></div>',
+      replace: true
+    })
+    vm.$mount()
+    expect(vm.$el.firstChild.getAttribute('open')).toBe('hello')
+  })
 })