# storybook-addon-a11y

This Storybook addon can be helpful to make your UI components more accessible.

[Framework Support](https://storybook.js.org/docs/react/api/frameworks-feature-support)

![Screenshot](https://raw.githubusercontent.com/storybookjs/storybook/next/code/addons/a11y/docs/screenshot.png)

## Getting started

First, install the addon.

```sh
$ yarn add @storybook/addon-a11y --dev
```

Add this line to your `main.js` file (create this file inside your Storybook config directory if needed).

```js
module.exports = {
  addons: ['@storybook/addon-a11y'],
};
```

And here's a sample story file to test the addon:

```js
import React from 'react';

export default {
  title: 'button',
};

export const Accessible = () => <button>Accessible button</button>;

export const Inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);
```

## Handling failing rules

When Axe reports accessibility violations in stories, there are multiple ways to handle these failures depending on your needs.

### Story-level overrides

At the Story level, override rules using `parameters.a11y.config.rules`.

```js
export const InputWithoutAutofill = () => <input type="text" autocomplete="nope" />;

InputWithoutAutofill.parameters = {
  a11y: {
    // Avoid doing this, as it will fully disable all accessibility checks for this story.
    disable: true,

    // Instead, override rules 👇
    // axe-core configurationOptions (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#parameters-1)
    config: {
      rules: [
        {
          // You can exclude some elements from failing a specific rule:
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // You can also signify that a violation will need to be fixed in the future
          // by overriding the result of a rule to return "Needs Review"
          // rather than "Violation" if the rule fails:
          id: 'landmark-complementary-is-top-level',
          reviewOnFail: true,
        },
      ],
    },
  },
};
```

Alternatively, you can disable specific rules in a Story:

```js
export const Inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);
Inaccessible.parameters = {
  a11y: {
    config: {
      rules: [{ id: 'color-contrast', enabled: false }],
    },
  },
};
```

Tip: clearly explain in a comment why a rule was overridden, it’ll help you and your team trace back why certain violations aren’t being reported or need to be addressed. For example:

```js
MyStory.parameters = {
  a11y: {
    config: {
      rules: [
        {
          // Allow `autocomplete="nope"` on form elements,
          // a workaround to disable autofill in Chrome.
          // @link https://bugs.chromium.org/p/chromium/issues/detail?id=468153
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // @fixme Color contrast of subdued text fails, as raised in issue #123.
          id: 'color-contrast',
          reviewOnFail: true,
        },
      ],
    },
  },
};
```

### Global overrides

When you want to ignore an accessibility rule or change its settings across all stories, set `parameters.a11y.config.rules` in your Storybook’s `preview.ts` file. This can be particularly useful for ignoring false positives commonly reported by Axe.

```ts
// .storybook/preview.ts

export const parameters = {
  a11y: {
    config: {
      rules: [
        {
          // This tells Axe to run the 'autocomplete-valid' rule on selectors
          // that match '*:not([autocomplete="nope"])' (all elements except [autocomplete="nope"]).
          // This is the safest way of ignoring a violation across all stories,
          // as Axe will only ignore very specific elements and keep reporting
          // violations on other elements of this rule.
          id: 'autocomplete-valid',
          selector: '*:not([autocomplete="nope"])',
        },
        {
          // To disable a rule across all stories, set `enabled` to `false`.
          // Use with caution: all violations of this rule will be ignored!
          id: 'autocomplete-valid',
          enabled: false,
        },
      ],
    },
  },
};
```

### Disabling checks

If you wish to entirely disable `a11y` checks for a subset of stories, you can control this with story parameters:

```js
export const MyNonCheckedStory = () => <SomeComponent />;
MyNonCheckedStory.parameters = {
  // Avoid doing this, as it fully disables all accessibility checks for this story,
  // and consider the techniques described above.
  a11y: { disable: true },
};
```

## Parameters

For more customizability use parameters to configure [aXe options](https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#api-name-axeconfigure).
You can override these options [at story level too](https://storybook.js.org/docs/react/configure/features-and-behavior#per-story-options).

```js
import React from 'react';
import { storiesOf, addDecorator, addParameters } from '@storybook/react';

export default {
  title: 'button',
  parameters: {
    a11y: {
      // optional selector which element to inspect
      element: '#root',
      // axe-core configurationOptions (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#parameters-1)
      config: {},
      // axe-core optionsParameter (https://github.com/dequelabs/axe-core/blob/develop/doc/API.md#options-parameter)
      options: {},
      // optional flag to prevent the automatic check
      manual: true,
    },
  },
};

export const accessible = () => <button>Accessible button</button>;

export const inaccessible = () => (
  <button style={{ backgroundColor: 'red', color: 'darkRed' }}>Inaccessible button</button>
);
```

## Roadmap

- Make UI accessible
- Show in story where violations are.
- Add more example tests
- Add tests
- Make CI integration possible
