declare el-collapse-transition in its dependents (#4728)

packages/collapse/src/collapse-item.vue

@@ -14,6 +14,7 @@
   </div>
 </template>
 <script>
+  import ElCollapseTransition from 'element-ui/src/transitions/collapse-transition';
   import Emitter from 'element-ui/src/mixins/emitter';
 
   export default {
@@ -23,6 +24,8 @@
 
     mixins: [Emitter],
 
+    components: { ElCollapseTransition },
+
     data() {
       return {
         contentWrapStyle: {

packages/menu/src/submenu.vue

@@ -26,6 +26,7 @@
   </li>
 </template>
 <script>
+  import ElCollapseTransition from 'element-ui/src/transitions/collapse-transition';
   import menuMixin from './menu-mixin';
   import Emitter from 'element-ui/src/mixins/emitter';
 
@@ -36,6 +37,8 @@
 
     mixins: [menuMixin, Emitter],
 
+    components: { ElCollapseTransition },
+
     props: {
       index: {
         type: String,

packages/select/src/option.vue

@@ -6,7 +6,8 @@
     v-show="visible"
     :class="{
       'selected': itemSelected,
-      'is-disabled': disabled || groupDisabled || limitReached
+      'is-disabled': disabled || groupDisabled || limitReached,
+      'hover': parent.hoverIndex === index
     }">
     <slot>
       <span>{{ currentLabel }}</span>

packages/tree/src/tree-node.vue

@@ -44,6 +44,7 @@
 </template>
 
 <script type="text/jsx">
+  import ElCollapseTransition from 'element-ui/src/transitions/collapse-transition';
   import ElCheckbox from 'element-ui/packages/checkbox';
   import emitter from 'element-ui/src/mixins/emitter';
 
@@ -65,6 +66,7 @@
     },
 
     components: {
+      ElCollapseTransition,
       ElCheckbox,
       NodeContent: {
         props: {