fix #6864: don't set ignoredElements' attributes to their default values

src/core/vdom/patch.js

@@ -104,18 +104,22 @@ export function createPatchFunction (backend) {
     }
   }
 
+  function isIgnoredElement (vnode) {
+    return (
+      config.ignoredElements.length &&
+      config.ignoredElements.some(ignore => {
+        return isRegExp(ignore)
+          ? ignore.test(vnode.tag)
+          : ignore === vnode.tag
+      })
+    )
+  }
+
   function isUnknownElement (vnode, inVPre) {
     return (
       !inVPre &&
       !vnode.ns &&
-      !(
-        config.ignoredElements.length &&
-        config.ignoredElements.some(ignore => {
-          return isRegExp(ignore)
-            ? ignore.test(vnode.tag)
-            : ignore === vnode.tag
-        })
-      ) &&
+      !vnode.isIgnoredElement &&
       config.isUnknownElement(vnode.tag)
     )
   }
@@ -131,6 +135,9 @@ export function createPatchFunction (backend) {
     const children = vnode.children
     const tag = vnode.tag
     if (isDef(tag)) {
+      if (isIgnoredElement(vnode)) {
+        vnode.isIgnoredElement = true
+      }
       if (process.env.NODE_ENV !== 'production') {
         if (data && data.pre) {
           creatingElmInVPre++

src/core/vdom/vnode.js

@@ -23,6 +23,7 @@ export default class VNode {
   asyncFactory: Function | void; // async component factory function
   asyncMeta: Object | void;
   isAsyncPlaceholder: boolean;
+  isIgnoredElement: boolean;
   ssrContext: Object | void;
   fnContext: Component | void; // real context vm for functional nodes
   fnOptions: ?ComponentOptions; // for SSR caching
@@ -58,6 +59,7 @@ export default class VNode {
     this.isComment = false
     this.isCloned = false
     this.isOnce = false
+    this.isIgnoredElement = false
     this.asyncFactory = asyncFactory
     this.asyncMeta = undefined
     this.isAsyncPlaceholder = false

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

@@ -38,14 +38,14 @@ function updateAttrs (oldVnode: VNodeWithData, vnode: VNodeWithData) {
     cur = attrs[key]
     old = oldAttrs[key]
     if (old !== cur) {
-      setAttr(elm, key, cur)
+      setAttr(elm, key, cur, vnode)
     }
   }
   // #4391: in IE9, setting type can reset value for input[type=radio]
   // #6666: IE/Edge forces progress value down to 1 before setting a max
   /* istanbul ignore if */
   if ((isIE || isEdge) && attrs.value !== oldAttrs.value) {
-    setAttr(elm, 'value', attrs.value)
+    setAttr(elm, 'value', attrs.value, vnode)
   }
   for (key in oldAttrs) {
     if (isUndef(attrs[key])) {
@@ -58,7 +58,14 @@ function updateAttrs (oldVnode: VNodeWithData, vnode: VNodeWithData) {
   }
 }
 
-function setAttr (el: Element, key: string, value: any) {
+function setAttr (el: Element, key: string, value: any, vnode: ?VNodeWithData) {
+  // The attributes are not set to their default values
+  // for elements in the ignoredElements array
+  // eg. <custom-tab-bar selected="tab1"></custom-tab-bar>
+  if (vnode && vnode.isIgnoredElement) {
+    el.setAttribute(key, value)
+    return
+  }
   if (isBooleanAttr(key)) {
     // set attribute for blank value
     // e.g. <option disabled>Select one</option>

test/unit/features/global-api/config.spec.js

@@ -49,7 +49,7 @@ describe('Global config', () => {
     it('should work', () => {
       Vue.config.ignoredElements = ['foo', /^ion-/]
       new Vue({
-        template: `<div><foo/><ion-foo/><ion-bar/></div>`
+        template: `<div><foo selected="tab1"/><ion-foo/><ion-bar/></div>`
       }).$mount()
       expect('Unknown custom element').not.toHaveBeenWarned()
       Vue.config.ignoredElements = []