added feature to select multiple, that allows show arrow

Author: a.shatalov

src/PropTypes.js

@@ -50,6 +50,7 @@ export const SelectPropTypes = {
   className: PropTypes.string,
   prefixCls: PropTypes.string,
   multiple: PropTypes.bool,
+  multipleShowArrow: PropTypes.bool,
   filterTreeNode: PropTypes.any,
   showSearch: PropTypes.bool,
   disabled: PropTypes.bool,

src/Select.jsx

@@ -944,7 +944,7 @@ class Select extends Component {
           {ctrlNode}
           {allowClear && this.state.value.length &&
           this.state.value[0].value ? clear : null}
-            {multiple || !props.showArrow ? null :
+            {multiple && !props.multipleShowArrow || !props.showArrow ? null :
               (<span
                 key="arrow"
                 className={`${prefixCls}-arrow`}

tests/Select.multiple.spec.js

@@ -95,4 +95,10 @@ describe('TreeSelect.multiple', () => {
     select(treeWrapper, 0);  // unselect
     expect(wrapper.find('input').node.value).toBe('');
   });
+
+  it('renders select multiple with arrow', () => {
+    const wrapper = render(createSelect({ multipleShowArrow: true }));
+
+    expect(wrapper.find('.rc-tree-select-arrow')).toHaveLength(1);
+  });
 });