fix(DatePicker): issues range-picker clear when value only has start …

…or end , close #3448

components/date-picker/__tests__/index-spec.js

@@ -1138,6 +1138,14 @@ describe('RangePicker', () => {
             assert(!ret[0]);
             assert(!ret[1]);
         });
+        // issue: https://github.com/alibaba-fusion/next/issues/3448
+        it('should clear range when only half value', () => {
+            let ret;
+            wrapper = mount(<RangePicker defaultValue={[, endValue]} onChange={val => (ret = val)} />);
+            wrapper.find('i.next-input-clear-icon').simulate('click');
+            assert(!ret[0]);
+            assert(!ret[1]);
+        });
 
         it('should input range value', function() {
             this.timeout(3000);

components/date-picker/range-picker.jsx

@@ -1075,7 +1075,7 @@ class RangePicker extends Component {
             [PANEL.TIME]: timePanel,
         }[state.panel];
 
-        const allowClear = state.startValue && state.endValue && hasClear;
+        const allowClear = (state.startValue || state.endValue) && hasClear;
         let [startPlaceholder, endPlaceholder] = placeholder || [];
 
         if (typeof placeholder === 'string') {