fix(NumberInput): handle case when input is invalid, resolves #436 (#836)

* fix(NumberInput): handle case when input is invalid, resolves #436

* fix(NumberInput): handle case when input is invalid, resolves #436

Author: rezak-otmani

src/components/NumberInput/NumberInput-test.js

@@ -123,6 +123,13 @@ describe('NumberInput', () => {
           let numberInput = wrapper.find('input');
           expect(numberInput.prop('value')).toEqual(5);
         });
+
+        it('should set invalidText when value is empty string', () => {
+          wrapper.setProps({ value: '' });
+          const invalidText = wrapper.find('.bx--form-requirement');
+          expect(invalidText.length).toEqual(1);
+          expect(invalidText.text()).toEqual('invalid text');
+        });
       });
     });
 

src/components/NumberInput/NumberInput.js

@@ -146,7 +146,7 @@ export default class NumberInput extends Component {
 
     const inputWrapperProps = {};
     let error = null;
-    if (invalid) {
+    if (invalid || this.state.value === '') {
       inputWrapperProps['data-invalid'] = true;
       error = <div className="bx--form-requirement">{invalidText}</div>;
     }