blitz-dom: attributes in a namespace get the special handling of the same-named attribute in no namespace

From the repository

This page is repros/blitz-dom-namespaced-attribute-special-cased/README.md, included when the site is built. Edit it there.

What niso does

Nothing yet. setAttributeNS("https://example.com/attributes", "style", …) on an element that also has a style attribute in no namespace re-parses the inline style from the namespaced one, so the element loses its inline style (tests/wpt/expectations.json: dom/nodes/namespaced-attribute-mutations.html, the four “change/replace a namespaced style attribute preserves … inline style” subtests).

Expected vs actual

DocumentMutator::set_attribute (packages/blitz-dom/src/mutator.rs:323-456) decides what an attribute means by its local name alone: id, class, style, value, disabled, checked, src, href and so on get their behaviour whatever their namespace. ElementData::attr (packages/blitz-dom/src/node/element.rs:492), which flush_style_attribute and the rest read the value through, also matches the local name only and returns whichever comes first. Per DOM and HTML, those attributes have their meaning only in no namespace.

• Expected: the element’s inline style still comes from its style attribute in no namespace (color: green).
• Actual: it comes from the namespaced style attribute, which was set first (after), so it is empty.

the null-namespace style attribute is Some("color: green")
expected: 1 inline declaration (color: green), from the style attribute in no namespace
actual:   0 inline declarations, from Some("after")

Run

CARGO_TARGET_DIR=~/.capy/work/repro-target cargo run

Exit status 1 while the bug reproduces, 0 once fixed. On Ubuntu, blitz needs sudo apt-get install -y libfontconfig-dev pkg-config.

Upstream main

Reproduces. Blitz main was at 9f9c8e321735890754b4a9970cb07765b8bf3c0c when tested (2026-11-08, git ls-remote https://github.com/DioxusLabs/blitz HEAD), with the same output and exit status 1.

Existing issue or PR

None found. Searched DioxusLabs/blitz issues and PRs (all states) for namespace attribute, namespaced, setAttributeNS, attribute namespace style. Closest: #1292 (“Follow-ups to :open: namespace check”), which checks the namespace for open only, and #1168/#1231, about dioxus-native-dom creating attributes in the HTML namespace.

Issue text

Title: Namespaced attributes get the behaviour of the same-named attribute in no namespace

Body:

DocumentMutator::set_attribute and ElementData::attr look attributes up by local name only. An element with a style attribute in no namespace and a style attribute in another namespace (setAttributeNS) takes its inline style from whichever comes first, and setting the namespaced one re-parses the inline style from it. The same goes for id, class, value, disabled and the rest of the attributes set_attribute special-cases.

let style = |ns: &str| QualName::new(None, Namespace::from(ns), LocalName::from("style"));
let mut m = doc.mutate();
m.set_attribute(div, style("https://example.com/attributes"), "before");
m.set_attribute(div, style(""), "color: green");
m.set_attribute(div, style("https://example.com/attributes"), "after");
// the div's style_attribute now has no declarations; expected color: green

Tested at be60597f67b3cece0456d26e8d7ff5a88600bbc5 and 9f9c8e321735890754b4a9970cb07765b8bf3c0c. Suggested fix: match ns!() as well as the local name in attr/attr_parsed and before the special cases in set_attribute/clear_attribute.