Attribute is not duplicated

Rule Type:
atomic
Rule ID:
e6952f
Last Modified:
June 3, 2021
Accessibility Requirements Mapping:
4.1.1 Parsing (Level A)
  • 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
  • Not required to 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:
Source code

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

Test Cases

Passed

Passed Example 1

No attributes are duplicated.

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

Passed Example 2

No attributes, therefore no attributes are duplicated.

<br />

Passed Example 3

Empty attributes, no attributes are duplicated.

<input type="checkbox" disabled readonly />

Passed Example 4

SVG, no attributes are duplicated.

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

Passed Example 5

Script, no attributes are duplicated. HTML or SVG code within a script should be ignored.

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

Failed

Failed Example 1

At least one attribute is duplicated.

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

Failed Example 2

Empty attributes, at least one attribute is duplicated.

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

Failed Example 3

SVG, at least one attribute is duplicated.

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

Inapplicable

Inapplicable Example 1

Code is XML, and 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

Code is JavaScript, and not HTML or SVG.

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

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.

Acknowledgements

This rule was written in the ACT Rules community group, with the support of the EU-funded WAI-Tools Project.

Authors

Changelog

This is the first version of this ACT rule.

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