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Cache element last child during HTML append #121

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Merged
kitsuyui merged 1 commit into from
Jul 3, 2026
Merged

Cache element last child during HTML append #121

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84 changes: 78 additions & 6 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ mod util;

use std::{
cell::{Cell, RefCell},
collections::HashMap,
convert::TryFrom,
};

Expand All @@ -20,7 +21,7 @@ use html5ever::{
LocalName, Namespace, QualName,
};
use sxd_document::{
dom::{ChildOfElement, Document, ParentOfChild},
dom::{ChildOfElement, Document, Element, ParentOfChild},
Package,
};

Expand All @@ -38,6 +39,7 @@ struct DocHtmlSink<'d> {
document_handle: Handle<'d>,
errors: RefCell<Vec<Error>>,
current_line: Cell<u64>,
last_children: RefCell<HashMap<Element<'d>, Option<ChildOfElement<'d>>>>,
}

impl<'d> DocHtmlSink<'d> {
Expand All @@ -49,6 +51,36 @@ impl<'d> DocHtmlSink<'d> {
document_handle,
errors: Default::default(),
current_line: Cell::new(0),
last_children: Default::default(),
}
}

fn cached_last_child(&self, elem: Element<'d>) -> Option<ChildOfElement<'d>> {
let mut last_children = self.last_children.borrow_mut();
if let Some(last_child) = last_children.get(&elem) {
return *last_child;
}

let last_child = elem.children().into_iter().last();
last_children.insert(elem, last_child);
last_child
}

fn set_cached_last_child(&self, elem: Element<'d>, last_child: Option<ChildOfElement<'d>>) {
self.last_children.borrow_mut().insert(elem, last_child);
}

fn invalidate_cached_last_child(&self, elem: Element<'d>) {
self.last_children.borrow_mut().remove(&elem);
}

fn invalidate_parent_last_child(&self, target: &Handle<'d>) {
if matches!(target, Handle::Document(_)) {
return;
}

if let Some(ParentOfChild::Element(parent)) = target.parent() {
self.invalidate_cached_last_child(parent);
}
}
}
Expand Down Expand Up @@ -136,8 +168,10 @@ impl<'d> TreeSink for DocHtmlSink<'d> {
// Explicit match makes the invariant visible; unreachable!() fires if
// a future html5ever version breaks the assumption.
match child {
NodeOrText::AppendNode(_) => {
let child = util::node_or_text_into_child_of_root(child);
NodeOrText::AppendNode(handle) => {
self.invalidate_parent_last_child(&handle);
let child =
util::node_or_text_into_child_of_root(NodeOrText::AppendNode(handle));
root.append_child(child);
}
NodeOrText::AppendText(_) => {
Expand All @@ -149,7 +183,8 @@ impl<'d> TreeSink for DocHtmlSink<'d> {
}
}
Handle::Element(elem, _, _) => {
let last = elem.children().into_iter().last();
let elem = *elem;
let last = self.cached_last_child(elem);

match (last, child) {
(Some(ChildOfElement::Text(x)), NodeOrText::AppendText(y)) => {
Expand All @@ -158,9 +193,14 @@ impl<'d> TreeSink for DocHtmlSink<'d> {
x.set_text(&new_text);
}
(_, child) => {
if let NodeOrText::AppendNode(ref handle) = child {
self.invalidate_parent_last_child(handle);
}

let document = elem.document();
let child = util::node_or_text_into_child_of_element(&document, child);
elem.append_child(child);
self.set_cached_last_child(elem, Some(child));
}
}
}
Expand Down Expand Up @@ -234,7 +274,15 @@ impl<'d> TreeSink for DocHtmlSink<'d> {
util::child_of_element_remove_from_parent(child);
}

if let NodeOrText::AppendNode(ref handle) = new_node {
self.invalidate_parent_last_child(handle);
}

util::parent_of_child_append_node_or_text(&parent, new_node);
if let ParentOfChild::Element(parent) = parent {
self.invalidate_cached_last_child(parent);
}

let parent_handle = Handle::from(parent);
for child in children {
let node_or_text = match child {
Expand All @@ -259,16 +307,22 @@ impl<'d> TreeSink for DocHtmlSink<'d> {
}

fn remove_from_parent(&self, target: &Self::Handle) {
self.invalidate_parent_last_child(target);
target.remove_from_parent();
}

fn reparent_children(&self, node: &Self::Handle, new_parent: &Self::Handle) {
let node = node.element_ref();
let new_parent = new_parent.element_ref();
let node = *node.element_ref();
let new_parent = *new_parent.element_ref();

let children = node.children();
let new_parent_last_child = children.last().copied();
node.clear_children();
self.set_cached_last_child(node, None);
new_parent.append_children(children);
if let Some(last_child) = new_parent_last_child {
self.set_cached_last_child(new_parent, Some(last_child));
}
}
}

Expand Down Expand Up @@ -463,6 +517,24 @@ mod tests {
assert_eq!(result, "Test");
}

#[test]
fn test_flat_sibling_text_append_pattern() {
// Exercises flat element/text siblings, where each trailing text append
// used to rescan all existing children of the parent element.
let mut html = String::from("<!DOCTYPE html><html><body>");
for i in 0..512 {
html.push_str("<span>");
html.push_str(&i.to_string());
html.push_str("</span>\n");
}
html.push_str("</body></html>");

let result = get_html_result(&html, "count(/html/body/span)").unwrap();
assert_eq!(result, "512");
let result = get_html_result(&html, "/html/body/span[512]/text()").unwrap();
assert_eq!(result, "511");
}

#[test]
fn test_comparison_with_xml() {
// This test is to ensure that the html parser is working as expected
Expand Down