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hovinenhovinen
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Remove hidden nodes from the acccessibility tree (#823)
* Remove hidden nodes from the acccessibility tree This is as per https://www.w3.org/TR/wai-aria-1.2/#tree_exclusion. It also facilitates testing: in cases where there is only one non-hidden element of a particular role, one can just query for that role without having to specify the query more narrowly. * Add tests * Move tests to blitz-tests * Make function into method of BlitzDomNode * Fix test * Remove redundant tests * Use HtmlDocument to simplify test setup * Remove extra check for hidden attribute -- it's not required * Also exclude from accessibility tree nodes descended from hidden nodes, as per the spec
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6 files changed

Lines changed: 202 additions & 2 deletions

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‎Cargo.lock‎

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‎Cargo.toml‎

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@@ -188,6 +188,7 @@ smol_str = "0.3"
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bitflags = "2.8.0"
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bytemuck = "1"
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rayon = "1"
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test-that = "0.5.2"
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thread_local = "1"
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[profile.profile]

‎packages/blitz-dom/src/accessibility.rs‎

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@@ -1,12 +1,23 @@
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use crate::{BaseDocument, ElementData, Node as BlitzDomNode, local_name};
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use accesskit::{Node as AccessKitNode, NodeId, Role, Tree, TreeId, TreeUpdate};
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use style::properties::longhands::visibility;
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impl BaseDocument {
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pub fn build_accessibility_tree(&self) -> TreeUpdate {
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let mut nodes = std::collections::HashMap::new();
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let mut window = AccessKitNode::new(Role::Window);
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let mut hidden_nodes = std::collections::HashSet::new();
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self.visit(|node_id, node| {
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if node.is_hidden_from_accessibility_tree()
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|| node
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.parent
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.map(|p| hidden_nodes.contains(&p))
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.unwrap_or(false)
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{
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hidden_nodes.insert(node_id);
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return;
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}
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let parent = node
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.parent
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.and_then(|parent_id| nodes.get_mut(&parent_id))
@@ -55,6 +66,11 @@ impl BaseDocument {
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builder.set_role(role);
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builder.set_html_tag(name);
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// https://www.w3.org/TR/wai-aria-1.2/#tree_exclusion
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if element_data.attr(local_name!("aria-hidden")) == Some("true") {
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builder.set_hidden();
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}
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} else if node.is_text_node() {
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builder.set_role(Role::TextRun);
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builder.set_value(node.text_content());
@@ -67,6 +83,21 @@ impl BaseDocument {
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}
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}
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impl BlitzDomNode {
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// https://www.w3.org/TR/wai-aria-1.2/#tree_exclusion
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fn is_hidden_from_accessibility_tree(&self) -> bool {
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self.try_stylo_element_data()
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.as_ref()
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.and_then(|s| s.get())
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.map(|s| {
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s.styles.is_display_none()
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|| s.styles.primary().clone_visibility()
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== visibility::computed_value::T::Hidden
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})
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.unwrap_or(false)
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}
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}
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fn role_from_name(name: &str) -> Option<Role> {
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match name {
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"alert" => Some(Role::Alert),

‎tests/blitz-tests/Cargo.toml‎

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Original file line numberDiff line numberDiff line change
@@ -31,6 +31,7 @@ accesskit = { workspace = true }
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markup5ever = { workspace = true }
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keyboard-types = { workspace = true }
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taffy = { workspace = true }
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test-that = { workspace = true }
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usvg = { workspace = true }
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[lib]

‎tests/blitz-tests/tests/accessibility_hidden.rs‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,145 @@
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use accesskit::{Node as AccessKitNode, Role};
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use blitz_dom::DocumentConfig;
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use blitz_html::{HtmlDocument, HtmlProvider};
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use blitz_traits::shell::{ColorScheme, Viewport};
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use std::sync::Arc;
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use test_that::prelude::*;
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#[test]
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fn includes_ordinary_div_as_node() -> TestResult<()> {
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let mut document =
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HtmlDocument::from_html("<html><div></div></html>", default_document_config());
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document.resolve(0.0);
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let tree_update = document.build_accessibility_tree();
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verify_that!(
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tree_update.nodes,
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contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::GenericContainer),
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is_hidden(): eq(false),
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})
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))
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)
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}
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#[test]
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fn excludes_div_with_hidden_attribute() -> TestResult<()> {
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let mut document =
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HtmlDocument::from_html("<html><div hidden></div></html>", default_document_config());
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document.resolve(0.0);
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let tree_update = document.build_accessibility_tree();
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verify_that!(
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tree_update.nodes,
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not(contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::GenericContainer)
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})
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)))
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)
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}
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#[test]
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fn excludes_div_with_display_none() -> TestResult<()> {
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let mut document = HtmlDocument::from_html(
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r#"<html><div style="display: none;"></div></html>"#,
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default_document_config(),
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);
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document.resolve(0.0);
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let tree_update = document.build_accessibility_tree();
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verify_that!(
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tree_update.nodes,
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not(contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::GenericContainer)
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})
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)))
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)
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}
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#[test]
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fn excludes_div_with_visibility_hidden() -> TestResult<()> {
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let mut document = HtmlDocument::from_html(
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r#"<html><div style="visibility: hidden;"></div></html>"#,
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default_document_config(),
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);
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document.resolve(0.0);
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76+
let tree_update = document.build_accessibility_tree();
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verify_that!(
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tree_update.nodes,
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not(contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::GenericContainer)
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})
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)))
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)
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}
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#[test]
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fn sets_hidden_flag_on_element_with_aria_hidden_attribute() -> TestResult<()> {
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let mut document = HtmlDocument::from_html(
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r#"<html><div aria-hidden="true"></div></html>"#,
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default_document_config(),
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);
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document.resolve(0.0);
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97+
let tree_update = document.build_accessibility_tree();
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verify_that!(
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tree_update.nodes,
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contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::GenericContainer),
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is_hidden(): eq(true),
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})
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))
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)
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}
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#[test]
112+
fn excludes_child_element_of_hidden_element() -> TestResult<()> {
113+
let mut document = HtmlDocument::from_html(
114+
r#"<html>
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<head/>
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<body>
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<div hidden="true">
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<button/>
119+
</div>
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</body>
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</html>"#,
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default_document_config(),
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);
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document.resolve(0.0);
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let tree_update = document.build_accessibility_tree();
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128+
verify_that!(
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tree_update.nodes,
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not(contains((
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anything(),
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matches_pattern!(AccessKitNode {
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role(): eq(Role::Button),
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})
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)))
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)
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}
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fn default_document_config() -> DocumentConfig {
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DocumentConfig {
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viewport: Some(Viewport::new(800, 600, 1.0, ColorScheme::Light)),
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html_parser_provider: Some(Arc::new(HtmlProvider) as _),
143+
..Default::default()
144+
}
145+
}

‎tests/blitz-tests/tests/accessibility_roles.rs‎

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Original file line numberDiff line numberDiff line change
@@ -192,7 +192,7 @@ fn a_semantic_page_has_no_unknown_elements() {
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<footer>End</footer>
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</body></html>"##;
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195-
// <html>, <head> and <body> have no roles of their own. Everything else in
195+
// <html> and <body> have no roles of their own. Everything else in
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// this document should map to something an assistive technology can use.
197-
assert_eq!(unknown_tags(html), vec!["body", "head", "html"]);
197+
assert_eq!(unknown_tags(html), vec!["body", "html"]);
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}

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