Add dropdown return key support

src/components/dropdown/dropdown.spec.tsx

@@ -0,0 +1,70 @@
+import {act} from 'react-dom/test-utils';
+import {mount, ReactWrapper} from 'enzyme';
+import * as React from 'react';
+
+import {DropDown} from './dropdown';
+
+describe('DropDown', () => {
+    let wrapper: ReactWrapper | null;
+
+    afterEach(() => {
+        if (wrapper) {
+            wrapper.unmount();
+            wrapper = null;
+        }
+    });
+
+    const renderDropdown = (onSelect: () => void) => mount(
+        <DropDown anchor={() => <button id='anchor'>anchor</button>} isMenu={true}>
+            <ul>
+                <li onClick={onSelect}>first</li>
+                <li>second</li>
+            </ul>
+        </DropDown>,
+    );
+
+    it('selects the first item when pressing Enter inside an open dropdown', async () => {
+        const onSelect = jest.fn();
+        wrapper = renderDropdown(onSelect);
+
+        await act(async () => {
+            wrapper!.find('.argo-dropdown__anchor').simulate('click', {stopPropagation: () => {}});
+            await Promise.resolve();
+        });
+        wrapper.update();
+
+        const preventDefault = jest.fn();
+        const event: any = {key: 'Enter', target: wrapper.find('.argo-dropdown__anchor').getDOMNode(), preventDefault};
+
+        (wrapper.instance() as any).selectTopResult(event);
+
+        expect(onSelect).toHaveBeenCalledTimes(1);
+        expect(preventDefault).toHaveBeenCalled();
+    });
+
+    it('ignores Enter when the dropdown is closed or when the target is outside', async () => {
+        const onSelect = jest.fn();
+        wrapper = renderDropdown(onSelect);
+
+        const closedEvent: any = {key: 'Enter', target: wrapper.find('.argo-dropdown__anchor').getDOMNode(), preventDefault: jest.fn()};
+
+        (wrapper.instance() as any).selectTopResult(closedEvent);
+
+        expect(onSelect).not.toHaveBeenCalled();
+
+        await act(async () => {
+            wrapper!.find('.argo-dropdown__anchor').simulate('click', {stopPropagation: () => {}});
+            await Promise.resolve();
+        });
+        wrapper.update();
+
+        const outside = document.createElement('div');
+        document.body.appendChild(outside);
+        const outsideEvent: any = {key: 'Enter', target: outside, preventDefault: jest.fn()};
+
+        (wrapper.instance() as any).selectTopResult(outsideEvent);
+
+        expect(onSelect).not.toHaveBeenCalled();
+        outside.remove();
+    });
+});

src/components/dropdown/dropdown.tsx

@@ -72,6 +72,8 @@ export class DropDown extends React.Component<DropDownProps, DropDownState> {
             if (this.state.opened && this.content && this.el) {
                 this.setState(this.refreshState());
             }
+        }), fromEvent<KeyboardEvent>(document, 'keydown').pipe(filter((event) => event.key === 'Enter' || event.keyCode === 13)).subscribe((event) => {
+            this.selectTopResult(event);
         })];
     }
 
@@ -87,6 +89,21 @@ export class DropDown extends React.Component<DropDownProps, DropDownState> {
         }
     }
 
+    private selectTopResult(event: KeyboardEvent) {
+        if (!this.state.opened || !this.content || !this.el) {
+            return;
+        }
+        const target = event.target as Node;
+        if (target && !this.el.contains(target) && !this.content.contains(target)) {
+            return;
+        }
+        const firstItem = this.content.querySelector('li') as HTMLElement;
+        if (firstItem) {
+            event.preventDefault();
+            firstItem.click();
+        }
+    }
+
     private refreshState() {
         const anchor = this.el.querySelector('.argo-dropdown__anchor') as HTMLElement;
         const {top, left} = anchor.getBoundingClientRect();