Proposed Attribute is not duplicated

Description

This rule checks that HTML and SVG starting tags do not contain duplicated attributes.

Applicability

This rule applies to any starting tag in an HTML or SVG document.

Note: This rule cannot be tested on the DOM Tree because the browser removes duplicates of any attribute that is already present on an element.

Expectation

For each test target, there are no duplicated attributes.

Assumptions

There are currently no assumptions.

Accessibility Support

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

Background

Bibliography

H94: Ensuring that elements do not contain duplicate attributes

Accessibility Requirements Mapping

4.1.1 Parsing (Level A)
- Learn more about 4.1.1 Parsing
- Required for conformance to WCAG 2.0 and later on level A and higher.
- Outcome mapping:
  - Any failed outcomes: success criterion is not satisfied
  - All passed outcomes: success criterion needs further testing
  - An inapplicable outcome: success criterion needs further testing
H94: Ensuring that elements do not contain duplicate attributes
- Learn more about technique H94
- Not required for conformance to any W3C accessibility recommendation.
- Outcome mapping:
  - Any failed outcomes: technique is not satisfied
  - All passed outcomes: technique is satisfied
  - An inapplicable outcome: technique is satisfied

Input Aspects

The following aspects are required in using this rule.

Source code (no link available)

Test Cases

Passed

Passed Example 1

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This img element contains no duplicated attributes.

<img src="/test-assets/shared/w3c-logo.png" alt="W3C logo" />

Passed Example 2

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This br element contains no attributes, so there is no duplicated attribute.

<br />

Passed Example 3

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This input element contains three different attributes, two of them being empty.

<input type="checkbox" disabled readonly />

Passed Example 4

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This SVG element contains no attributes.

<svg>
	<line x1="0" y1="0" x2="200" y2="200" style="stroke-width:2" />
</svg>

Passed Example 5

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This script element contains duplicated attributes, but they are ignored because they are placed within the script tag.

<script>
	var foo = '<img src="/test-assets/shared/w3c-logo.png" alt="" alt="W3C logo" />'
</script>

Failed

Failed Example 1

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This img element contains a duplicated alt attribute.

<img src="/test-assets/shared/w3c-logo.png" alt="" alt="W3C logo" />

Failed Example 2

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This input element contains a duplicate disabled attribute.

<input type="checkbox" disabled="disabled" disabled readonly />

Failed Example 3

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This line element contains duplicate x1 and duplicate y1 attributes.

<svg>
	<line x1="0" y1="0" x1="200" y1="200" style="stroke-width:2" />
</svg>

Inapplicable

Inapplicable Example 1

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This code is XML, not HTML or SVG.

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:earl="http://www.w3.org/ns/earl#">
  <earl:TestResult rdf:about="#result"></earl:TestResult>
</rdf:RDF>

Inapplicable Example 2

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This code is JavaScript, not HTML or SVG.

var foo = '<img src="/test-assets/shared/w3c-logo.png" alt="W3C logo" />'

Glossary

Outcome

An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Inapplicable: No part of the test subject matches the applicability
Passed: A test target meets all expectations
Failed: A test target does not meet all expectations

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.