xml:lang not handled correctly

[mirabilos]

Product

axe-core

Product Version

No response

Latest Version

• I have tested the issue with the latest version of the product

Issue Description

https://www.webpagetest.org links to https://dequeuniversity.com/rules/axe/4.4/html-has-lang?application=axeAPI describing that the html tag must have a lang attribute.

This is not true, however, for XHTML documents even if served as HTML because the DTD doesn’t have lang but xml:lang only.

And yes, it’s totally okay to serve XHTML documents written in compatibility mode (e.g. with space before />) as text/html; in fact, this is good as recommended nowadays because it’s less buggy. It may not help the latest browsers as much as serving it as XML, but it does help authoring tools or download postprocessing tools which can go straight at it in XML.

[WilcoFiers]

Axe-core's page-has-lang rule does allow xml:lang on XHTML doctype. These rule help pages aren't necessarily fully documenting everything the rule will do. They are designed to help developers solve a problem. Adding a lang attribute solves the problem, even if in some niche cases there is a second option.

Support for xml:lang in browsers and screen readers has been decreasing over the last few years. None of the major browser+AT combinations still support xml:lang in an HTML document, and they currently all prioritise lang over xml:lang if both exist in a page served with application/xhtml+xml.

[mirabilos]

Wilco Fiers dixit:

Support for `xml:lang` in browsers and screen readers has been decreasing over the last few years. None of the major browser+AT combinations still support xml:lang in an HTML document, and they currently all prioritise lang over xml:lang if both exist in a page served with `application/xhtml+xml`.

The DTD does not allow the lang attribute though. bye, //mirabilos --

> Why don't you use JavaScript? I also don't like enabling JavaScript in Because I use lynx as browser.

+1 -- Octavio Alvarez, me and ⡍⠁⠗⠊⠕ (Mario Lang) on debian-devel