# label-has-for

Enforce label tags have associated control.

There are two supported ways to associate a label with a control:

- nesting: by wrapping a control in a label tag
- id: by using the prop `htmlFor` as in `htmlFor=[ID of control]`

To fully cover 100% of assistive devices, you're encouraged to validate for both nesting and id.

## Rule details

This rule takes one optional object argument of type object:

```json
{
    "rules": {
        "jsx-a11y/label-has-for": [ 2, {
            "components": [ "Label" ],
            "required": {
                "every": [ "nesting", "id" ]
            },
            "allowChildren": false,
        }],
    }
}
```

For the `components` option, these strings determine which JSX elements (**always including** `<label>`) should be checked for having `htmlFor` prop. This is a good use case when you have a wrapper component that simply renders a `label` element (like in React):

```js
// Label.js
const Label = props => {
  const {
    htmlFor,
    ...otherProps
  } = props;

  return (
    <label htmlFor={htmlFor} {...otherProps} />
  );
}

...

// CreateAccount.js (for example)
...
return (
  <form>
    <input id="firstName" type="text" />
    <Label htmlFor="firstName">First Name</Label>
  </form>
);
```

The `required` option (defaults to `"required": { "every": ["nesting", "id"] }`) determines which checks are activated. You're allowed to pass in one of the following types:

- string: must be one of the acceptable strings (`"nesting"` or `"id"`)
- object, must have one of the following properties:

  - some: an array of acceptable strings, will pass if ANY of the requested checks passed
  - every: an array of acceptable strings, will pass if ALL of the requested checks passed

The `allowChildren` option (defaults to `false`) determines whether `{children}` content is allowed to be passed into a `label` element. For example, the following pattern, by default, is not allowed:

```js
<label>{children}</label>
```

However, if `allowChildren` is set to `true`, no error will be raised. If you want to pass in `{children}` content without raising an error, because you cannot be sure what `{children}` will render, then set `allowChildren` to `true`.

Note that passing props as spread attribute without `htmlFor` explicitly defined will cause this rule to fail. Explicitly pass down `htmlFor` prop for rule to pass. The prop must have an actual value to pass. Use `Label` component above as a reference. **It is a good thing to explicitly pass props that you expect to be passed for self-documentation.** For example:

#### Bad
```jsx
function Foo(props) {
  return <label {...props} />
}
```

#### Good
```jsx
function Foo({ htmlFor, ...props}) {
    return <label htmlFor={htmlFor} {...props} />
}

// OR

function Foo(props) {
    const {
        htmlFor,
        ...otherProps
    } = props;

   return <label htmlFor={htmlFor} {...otherProps} />
}
```

### Succeed
```jsx
<label htmlFor="firstName">
  <input type="text" id="firstName" />
  First Name
</label>
```

### Fail
```jsx
<input type="text" id="firstName" />
<label>First Name</label>
```
