Addon-A11y: Show errors, reset config properly

addons/a11y/README.md

@@ -56,7 +56,6 @@ import { withA11y } from '@storybook/addon-a11y';
 addDecorator(withA11y)
 addParameters({
   a11y: {
-    // ... axe options
     element: '#root', // optional selector which element to inspect
     config: {}, // axe-core configurationOptions (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#parameters-1)
     options: {} // axe-core optionsParameter (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#options-parameter)

addons/a11y/src/components/A11YPanel.test.js

@@ -63,7 +63,7 @@ function ThemedA11YPanel(props) {
 }
 
 describe('A11YPanel', () => {
-  it('should register STORY_RENDERED and RESULT updater on mount', () => {
+  it('should register STORY_RENDERED, RESULT and ERROR updater on mount', () => {
     // given
     const api = createApi();
     expect(api.on).not.toHaveBeenCalled();
@@ -72,9 +72,10 @@ describe('A11YPanel', () => {
     mount(<ThemedA11YPanel api={api} />);
 
     // then
-    expect(api.on.mock.calls.length).toBe(2);
+    expect(api.on.mock.calls.length).toBe(3);
     expect(api.on.mock.calls[0][0]).toBe(STORY_RENDERED);
     expect(api.on.mock.calls[1][0]).toBe(EVENTS.RESULT);
+    expect(api.on.mock.calls[2][0]).toBe(EVENTS.ERROR);
   });
 
   it('should request a run on tab activation', () => {
@@ -93,7 +94,7 @@ describe('A11YPanel', () => {
     expect(wrapper.find(ScrollArea).length).toBe(0);
   });
 
-  it('should deregister STORY_RENDERED and RESULT updater on unmount', () => {
+  it('should deregister STORY_RENDERED, RESULT and ERROR updater on unmount', () => {
     // given
     const api = createApi();
     const wrapper = mount(<ThemedA11YPanel api={api} />);
@@ -103,9 +104,10 @@ describe('A11YPanel', () => {
     wrapper.unmount();
 
     // then
-    expect(api.off.mock.calls.length).toBe(2);
+    expect(api.off.mock.calls.length).toBe(3);
     expect(api.off.mock.calls[0][0]).toBe(STORY_RENDERED);
     expect(api.off.mock.calls[1][0]).toBe(EVENTS.RESULT);
+    expect(api.off.mock.calls[2][0]).toBe(EVENTS.ERROR);
   });
 
   it('should update run result', () => {

addons/a11y/src/components/A11YPanel.tsx

@@ -46,26 +46,35 @@ const Incomplete = styled.span<{}>(({ theme }) => ({
   color: theme.color.warning,
 }));
 
+const centeredStyle = {
+  display: 'flex',
+  alignItems: 'center',
+  justifyContent: 'center',
+  height: '100%',
+};
+
 const Loader = styled(({ className }) => (
   <div className={className}>
     <Icon inline icon="sync" status="running" /> Please wait while the accessibility scan is running
     ...
   </div>
-))({
-  display: 'flex',
-  alignItems: 'center',
-  justifyContent: 'center',
-  height: '100%',
-});
+))(centeredStyle);
 Loader.displayName = 'Loader';
 
-interface A11YPanelState {
-  status: string;
+interface A11YPanelNormalState {
+  status: 'ready' | 'ran' | 'running';
   passes: Result[];
   violations: Result[];
   incomplete: Result[];
 }
 
+interface A11YPanelErrorState {
+  status: 'error';
+  error: unknown;
+}
+
+type A11YPanelState = A11YPanelNormalState | A11YPanelErrorState;
+
 interface A11YPanelProps {
   active: boolean;
   api: API;
@@ -84,6 +93,7 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
 
     api.on(STORY_RENDERED, this.request);
     api.on(EVENTS.RESULT, this.onUpdate);
+    api.on(EVENTS.ERROR, this.onError);
   }
 
   componentDidUpdate(prevProps: A11YPanelProps) {
@@ -101,6 +111,7 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
     const { api } = this.props;
     api.off(STORY_RENDERED, this.request);
     api.off(EVENTS.RESULT, this.onUpdate);
+    api.off(EVENTS.ERROR, this.onError);
   }
 
   onUpdate = ({ passes, violations, incomplete }: AxeResults) => {
@@ -124,6 +135,13 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
     );
   };
 
+  onError = (error: unknown) => {
+    this.setState({
+      status: 'error',
+      error,
+    });
+  };
+
   request = () => {
     const { api, active } = this.props;
 
@@ -142,8 +160,22 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
   };
 
   render() {
-    const { passes, violations, incomplete, status } = this.state;
     const { active } = this.props;
+    if (!active) return null;
+
+    // eslint-disable-next-line react/destructuring-assignment
+    if (this.state.status === 'error') {
+      const { error } = this.state;
+      return (
+        <div style={centeredStyle}>
+          The accessibility scan encountered an error.
+          <br />
+          {error}
+        </div>
+      );
+    }
+
+    const { passes, violations, incomplete, status } = this.state;
 
     let actionTitle;
     if (status === 'ready') {
@@ -162,7 +194,7 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
       );
     }
 
-    return active ? (
+    return (
       <Fragment>
         <Provider store={store}>
           {status === 'running' ? (
@@ -218,6 +250,6 @@ export class A11YPanel extends Component<A11YPanelProps, A11YPanelState> {
           />
         </Provider>
       </Fragment>
-    ) : null;
+    );
   }
 }

addons/a11y/src/components/__snapshots__/A11YPanel.test.js.snap

@@ -177,6 +177,10 @@ exports[`A11YPanel should render report 1`] = `
             "storybook/a11y/result",
             [Function],
           ],
+          Array [
+            "storybook/a11y/error",
+            [Function],
+          ],
         ],
         "results": Array [
           Object {
@@ -187,6 +191,10 @@ exports[`A11YPanel should render report 1`] = `
             "type": "return",
             "value": undefined,
           },
+          Object {
+            "type": "return",
+            "value": undefined,
+          },
         ],
       },
     }

addons/a11y/src/constants.ts

@@ -6,5 +6,6 @@ export const ADD_ELEMENT = 'ADD_ELEMENT';
 export const CLEAR_ELEMENTS = 'CLEAR_ELEMENTS';
 const RESULT = `${ADDON_ID}/result`;
 const REQUEST = `${ADDON_ID}/request`;
+const ERROR = `${ADDON_ID}/error`;
 
-export const EVENTS = { RESULT, REQUEST };
+export const EVENTS = { RESULT, REQUEST, ERROR };

addons/a11y/src/index.ts

@@ -39,20 +39,29 @@ const run = (element: ElementContext, config: Spec, options: RunOptions) => {
             restoreScroll: true,
           } as RunOptions) // cast to RunOptions is necessary because axe types are not up to date
       )
-      .then(report);
+      .then(report)
+      .catch(error => addons.getChannel().emit(EVENTS.ERROR, String(error)));
   });
 };
 
 if (module && module.hot && module.hot.decline) {
   module.hot.decline();
 }
 
+let storedDefaultSetup: Setup | null = null;
+
 export const withA11y = makeDecorator({
   name: 'withA11Y',
   parameterName: PARAM_KEY,
   wrapper: (getStory, context, { parameters }) => {
     if (parameters) {
-      setup = parameters as Setup;
+      if (storedDefaultSetup === null) {
+        storedDefaultSetup = { ...setup };
+      }
+      Object.assign(setup, parameters as Setup);
+    } else if (storedDefaultSetup !== null) {
+      Object.assign(setup, storedDefaultSetup);
+      storedDefaultSetup = null;
     }
     addons.getChannel().on(EVENTS.REQUEST, () => run(setup.element, setup.config, setup.options));