Add discrepancy handling to A11yPanel

code/addons/a11y/src/components/A11YPanel.tsx

@@ -8,6 +8,7 @@ import { CheckIcon, SyncIcon } from '@storybook/icons';
 import { useA11yContext } from './A11yContext';
 import { Report } from './Report';
 import { Tabs } from './Tabs';
+import { TestDiscrepancyMessage } from './TestDiscrepancyMessage';
 
 export enum RuleType {
   VIOLATION,
@@ -43,7 +44,7 @@ const Centered = styled.span({
 });
 
 export const A11YPanel: React.FC = () => {
-  const { results, status, handleManual, error } = useA11yContext();
+  const { results, status, handleManual, error, discrepancy } = useA11yContext();
 
   const manualActionItems = useMemo(
     () => [{ title: 'Run test', onClick: handleManual }],
@@ -106,31 +107,35 @@ export const A11YPanel: React.FC = () => {
 
   return (
     <>
-      {status === 'initial' && <Centered>Initializing...</Centered>}
-      {status === 'manual' && (
-        <>
-          <Centered>Manually run the accessibility scan.</Centered>
-          <ActionBar key="actionbar" actionItems={manualActionItems} />
-        </>
-      )}
-      {status === 'running' && (
-        <Centered>
-          <RotatingIcon size={12} /> Please wait while the accessibility scan is running ...
-        </Centered>
-      )}
-      {(status === 'ready' || status === 'ran') && (
+      {discrepancy && <TestDiscrepancyMessage discrepancy={discrepancy} />}
+      {status === 'ready' || status === 'ran' ? (
         <>
           <ScrollArea vertical horizontal>
             <Tabs key="tabs" tabs={tabs} />
           </ScrollArea>
           <ActionBar key="actionbar" actionItems={readyActionItems} />
         </>
-      )}
-      {status === 'error' && (
-        <Centered>
-          The accessibility scan encountered an error.
-          <br />
-          {typeof error === 'string' ? error : JSON.stringify(error)}
+      ) : (
+        <Centered style={{ marginTop: discrepancy ? '1em' : 0 }}>
+          {status === 'initial' && 'Initializing...'}
+          {status === 'manual' && (
+            <>
+              <>Manually run the accessibility scan.</>
+              <ActionBar key="actionbar" actionItems={manualActionItems} />
+            </>
+          )}
+          {status === 'running' && (
+            <>
+              <RotatingIcon size={12} /> Please wait while the accessibility scan is running ...
+            </>
+          )}
+          {status === 'error' && (
+            <>
+              The accessibility scan encountered an error.
+              <br />
+              {typeof error === 'string' ? error : JSON.stringify(error)}
+            </>
+          )}
         </Centered>
       )}
     </>

code/addons/a11y/src/components/A11yContext.tsx

@@ -1,5 +1,5 @@
 import type { FC, PropsWithChildren } from 'react';
-import React, { createContext, useCallback, useContext, useEffect, useState } from 'react';
+import React, { createContext, useCallback, useContext, useEffect, useMemo, useState } from 'react';
 
 import {
   STORY_FINISHED,
@@ -10,6 +10,7 @@ import {
   useAddonState,
   useChannel,
   useParameter,
+  useStorybookApi,
   useStorybookState,
 } from 'storybook/internal/manager-api';
 import type { Report } from 'storybook/internal/preview-api';
@@ -19,9 +20,10 @@ import { HIGHLIGHT } from '@storybook/addon-highlight';
 
 import type { AxeResults, Result } from 'axe-core';
 
-import { ADDON_ID, EVENTS } from '../constants';
+import { ADDON_ID, EVENTS, TEST_PROVIDER_ID } from '../constants';
 import type { A11yParameters } from '../params';
 import type { A11YReport } from '../types';
+import type { TestDiscrepancy } from './TestDiscrepancyMessage';
 
 export interface Results {
   passes: Result[];
@@ -40,6 +42,7 @@ export interface A11yContextStore {
   setStatus: (status: Status) => void;
   error: unknown;
   handleManual: () => void;
+  discrepancy: TestDiscrepancy;
 }
 
 const colorsByType = [
@@ -63,6 +66,7 @@ export const A11yContext = createContext<A11yContextStore>({
   status: 'initial',
   error: undefined,
   handleManual: () => {},
+  discrepancy: null,
 });
 
 const defaultResult = {
@@ -80,12 +84,15 @@ export const A11yContextProvider: FC<PropsWithChildren> = (props) => {
 
   const getInitialStatus = useCallback((manual = false) => (manual ? 'manual' : 'initial'), []);
 
+  const api = useStorybookApi();
   const [results, setResults] = useAddonState<Results>(ADDON_ID, defaultResult);
   const [tab, setTab] = useState(0);
   const [error, setError] = React.useState<unknown>(undefined);
   const [status, setStatus] = useState<Status>(getInitialStatus(parameters.manual!));
   const [highlighted, setHighlighted] = useState<string[]>([]);
+
   const { storyId } = useStorybookState();
+  const storyStatus = api.getCurrentStoryStatus();
 
   const handleToggleHighlight = useCallback((target: string[], highlight: boolean) => {
     setHighlighted((prevHighlighted) =>
@@ -178,6 +185,28 @@ export const A11yContextProvider: FC<PropsWithChildren> = (props) => {
     emit(HIGHLIGHT, { elements: highlighted, color: colorsByType[tab] });
   }, [emit, highlighted, tab]);
 
+  const discrepancy: TestDiscrepancy = useMemo(() => {
+    const storyStatusA11y = storyStatus[TEST_PROVIDER_ID]?.status;
+
+    if (storyStatusA11y) {
+      if (storyStatusA11y === 'success' && results.violations.length > 0) {
+        return 'cliPassedBrowserFailed';
+      }
+
+      if (storyStatusA11y === 'error' && results.violations.length === 0) {
+        if (status === 'ready' || status === 'ran') {
+          return 'browserPassedCliFailed';
+        }
+
+        if (status === 'manual') {
+          return 'cliFailedButModeManual';
+        }
+      }
+    }
+
+    return null;
+  }, [results.violations.length, status, storyStatus]);
+
   return (
     <A11yContext.Provider
       value={{
@@ -191,6 +220,7 @@ export const A11yContextProvider: FC<PropsWithChildren> = (props) => {
         setStatus,
         error,
         handleManual,
+        discrepancy,
       }}
       {...props}
     />

code/addons/a11y/src/components/TestDiscrepancyMessage.tsx

@@ -0,0 +1,73 @@
+import React, { useMemo } from 'react';
+
+import { Link } from 'storybook/internal/components';
+import { useStorybookApi } from 'storybook/internal/manager-api';
+import { styled } from 'storybook/internal/theming';
+
+import { DOCUMENTATION_DISCREPANCY_LINK } from '../constants';
+
+const Wrapper = styled.div(({ theme: { color, typography, background } }) => ({
+  textAlign: 'start',
+  padding: '11px 15px',
+  fontSize: `${typography.size.s2}px`,
+  fontWeight: typography.weight.regular,
+  lineHeight: '1rem',
+  background: background.app,
+  borderBottom: `1px solid ${color.border}`,
+  color: color.defaultText,
+  backgroundClip: 'padding-box',
+  position: 'relative',
+  code: {
+    fontSize: `${typography.size.s1 - 1}px`,
+    color: 'inherit',
+    margin: '0 0.2em',
+    padding: '0 0.2em',
+    background: 'rgba(255, 255, 255, 0.8)',
+    borderRadius: '2px',
+    boxShadow: '0 0 0 1px rgba(0, 0, 0, 0.1)',
+  },
+}));
+
+export type TestDiscrepancy =
+  | 'browserPassedCliFailed'
+  | 'cliPassedBrowserFailed'
+  | 'cliFailedButModeManual'
+  | null;
+
+interface TestDiscrepancyMessageProps {
+  discrepancy: TestDiscrepancy;
+}
+export const TestDiscrepancyMessage = ({ discrepancy }: TestDiscrepancyMessageProps) => {
+  const api = useStorybookApi();
+  const docsUrl = api.getDocsUrl({
+    subpath: DOCUMENTATION_DISCREPANCY_LINK,
+    versioned: true,
+    renderer: true,
+  });
+
+  const message = useMemo(() => {
+    switch (discrepancy) {
+      case 'browserPassedCliFailed':
+        return 'Accessibility checks passed in this browser but failed in the CLI.';
+      case 'cliPassedBrowserFailed':
+        return 'Accessibility checks passed in the CLI but failed in this browser.';
+      case 'cliFailedButModeManual':
+        return 'Accessibility checks failed in the CLI. Run the tests manually to see the results.';
+      default:
+        return null;
+    }
+  }, [discrepancy]);
+
+  if (!message) {
+    return null;
+  }
+
+  return (
+    <Wrapper>
+      {message}{' '}
+      <Link href={docsUrl} target="_blank" withArrow>
+        Learn what could cause this
+      </Link>
+    </Wrapper>
+  );
+};

code/addons/a11y/src/constants.ts

@@ -7,4 +7,9 @@ const RUNNING = `${ADDON_ID}/running`;
 const ERROR = `${ADDON_ID}/error`;
 const MANUAL = `${ADDON_ID}/manual`;
 
+export const DOCUMENTATION_LINK = 'writing-tests/accessibility-testing';
+export const DOCUMENTATION_DISCREPANCY_LINK = `${DOCUMENTATION_LINK}#what-happens-when-there-are-different-results-in-multiple-environments`;
+
+export const TEST_PROVIDER_ID = 'storybook/addon-a11y/test-provider';
+
 export const EVENTS = { RESULT, REQUEST, RUNNING, ERROR, MANUAL };