Tooltip: prevent hidding when hovering tooltip, close #2633 (#2654)

* Tooltip: prevent hidding when hovering tooltip, close #2633

* Fix test

packages/tooltip/src/main.js

 import Popper from 'element-ui/src/utils/vue-popper';
+import debounce from 'throttle-debounce/debounce';
 import Vue from 'vue';
 
 export default {
@@ -43,6 +44,8 @@ export default {
         return this.node;
       }
     }).$mount();
+
+    this.debounceClose = debounce(200, () => this.handleClosePopper());
   },
 
   render(h) {
@@ -51,6 +54,8 @@ export default {
         name={ this.transition }
         onAfterLeave={ this.doDestroy }>
         <div
+          onMouseleave={ () => { this.debounceClose(); this.togglePreventClose(); } }
+          onMouseenter= { this.togglePreventClose }
           ref="popper"
           v-show={!this.disabled && this.showPopper}
           class={
@@ -67,7 +72,7 @@ export default {
     const on = vnode.data.on = vnode.data.on || {};
 
     on.mouseenter = this.addEventHandle(on.mouseenter, this.handleShowPopper);
-    on.mouseleave = this.addEventHandle(on.mouseleave, this.handleClosePopper);
+    on.mouseleave = this.addEventHandle(on.mouseleave, this.debounceClose);
     data.staticClass = this.concatClass(data.staticClass, 'el-tooltip');
 
     return vnode;
@@ -83,6 +88,7 @@ export default {
     },
 
     concatClass(a, b) {
+      if (a && a.indexOf(b) > -1) return a;
       return a ? b ? (a + ' ' + b) : a : (b || '');
     },
 
@@ -95,9 +101,13 @@ export default {
     },
 
     handleClosePopper() {
-      if (this.manual) return;
+      if (this.preventClose || this.manual) return;
       clearTimeout(this.timeout);
       this.showPopper = false;
+    },
+
+    togglePreventClose() {
+      this.preventClose = !this.preventClose;
     }
   }
 };

test/unit/specs/tooltip.spec.js

@@ -78,9 +78,12 @@ describe('Tooltip', () => {
     triggerEvent(tooltip.$el, 'mouseenter');
     it('popperElm is exist', () => expect(tooltip.popperElm).to.exist);
     it('showPopper is true', () => expect(tooltip.showPopper).to.true);
-    it('close popper', () => {
+    it('close popper', done => {
       triggerEvent(tooltip.$el, 'mouseleave');
-      expect(tooltip.showPopper).to.false;
+      setTimeout(() => {
+        expect(tooltip.showPopper).to.false;
+        done();
+      }, 300);
     });
   });