SIA-R63`<object>` elements have an accessible name

Accessibility requirements

This rule tests conformance of the following accessibility requirements:

This rule checks that <object> elements have an accessible name.

This rule applies to every <object> element in the HTML namespace that is included in the accessibility tree and embeds a resource whose MIME type is either image, or audio or video.

This rule makes the following assumption:

The <object> element is not used to embed textual content, such as another HTML document. For this purpose, an <iframe> should instead be used.

This rule has no known accessibility support concerns.

This <object> element has an accessible name given by its aria-label attribute.

<object aria-label="A placeholder image" data="foo.jpg" />

This <object> element has an empty accessible name.

<object data="foo.jpg" />

<object aria-hidden="true" data="foo.jpg" />

There is no <object> element.

<img aria-label="A placeholder image" src="foo.jpg" />

<object> elements have no implicit ARIA role, but are nonetheless exposed to assistive technologies by user agents; Alfa thus applies to any <object> element that is not programmatically hidden.
Alfa does not sniff the MIME type of the embedded resource; instead it relies on both the type attribute (if any) and the extension of the filename in the data attribute.