New Rule: Valid use of image file name in accessible name

[Brynanders]

---

name: accessible name is image file name
description: |
This rule checks that the accessible name of an image is not its file name.

success_criterion:

• 1.1.1 # Non-text Content

test_aspects

• DOM Tree
• CSS Styling

authors:

• Bryn Anderson

---

Applicability

The rule applies to any HTML img element that is exposed to assistive technologies, where the element has a non-empty alt attribute that is equal to the accessible name of the element, and where the alt attribute of the element references the file name and extension of the src attribute of the element.

Expectation

Each test target has an alt attribute that serves as an appropriate text alternative as described in F30: Failure of Success Criterion 1.1.1 and 1.2.1 due to using text alternatives that are not alternatives (e.g., filenames or placeholder text).

Assumptions

There are currently no assumptions

Accessibility support

There are no major accessibility support issues known for this rule.

Background

• Understanding Success Criterion 1.1.1: Non-text Content
• F30: Failure of Success Criterion 1.1.1 and 1.2.1 due to using text alternatives that are not alternatives (e.g., filenames or placeholder text)

Test Cases

Pass example 1

Image depicting a PDF file format, uses the .pdf extension in the accessible name.

<img scr="/example.pdf" alt="an example of a .pdf file">

Failure example 1

The accessible name is the image file name and does not serve as an appropriate text alternative.

<img src="/image.jpg" alt="image.jpg file">

Inapplicable example 1

No reference to a file extension or file path in the accessible name.

<img src="/example.pdf" alt="an example of a PDF file">

[Brynanders]

Wondering if this rule should be confined to accessible names for images that reference their own image files... or if it should look for any file reference like I have done so far?

[kasperisager]

I'm wondering if this note can be left out:

Leading and trailing whitespace and difference in case sensitivity should be ignored.

Given that some file systems are case sensitive and that file system paths for sure are whitespace sensitive, it seems to be best to compare the src and alt attributes verbatim.

[Brynanders]

Created PR #263