perf: Avoid creating unused caches

Signed-off-by: Dmitry Dygalo <dmitry@dygalo.dev>

Author: Stranger6667

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Performance
 
 - Slightly improve performance of HTML serialization.
+- Avoid creating unused caches.
 
 ## [0.14.4] - 2024-12-27
 

bindings/c/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+### Performance
+
+- Slightly improve performance of HTML serialization.
+- Avoid creating unused caches.
+
 ## [0.14.4] - 2024-12-27
 
 ### Changed

bindings/javascript/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+### Performance
+
+- Slightly improve performance of HTML serialization.
+- Avoid creating unused caches.
+
 ### Changed
 
 - Bump MSRV to `1.71.1`.

bindings/python/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+### Performance
+
+- Slightly improve performance of HTML serialization.
+- Avoid creating unused caches.
+
 ### Changed
 
 - Update `PyO3` to `0.23.0`.

bindings/ruby/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+### Performance
+
+- Slightly improve performance of HTML serialization.
+- Avoid creating unused caches.
+
 ### Changed
 
 - Bump MSRV to `1.71.1`.

css-inline/src/html/document.rs

@@ -297,16 +297,10 @@ impl Document {
     pub(crate) fn select<'a, 'b, 'c>(
         &'a self,
         selectors: &'b str,
-        caches: &'c mut [NthIndexCache],
+        caches: &'c mut NthIndexCache,
     ) -> Result<Select<'a, 'c>, ParseError<'b>> {
         select(self, selectors, caches)
     }
-
-    pub(crate) fn build_caches(&self) -> Vec<NthIndexCache> {
-        (0..self.elements.len())
-            .map(|_| NthIndexCache::default())
-            .collect()
-    }
 }
 
 impl std::ops::Index<NodeId> for Document {

css-inline/src/html/iter.rs

@@ -6,26 +6,27 @@ use super::{
     Specificity,
 };
 use selectors::NthIndexCache;
-use std::iter::Zip;
 
 /// Compile selectors from a string and create an element iterator that yields elements matching these selectors.
 #[inline]
 pub(crate) fn select<'a, 'b, 'c>(
     document: &'a Document,
     selectors: &'b str,
-    caches: &'c mut [NthIndexCache],
+    caches: &'c mut NthIndexCache,
 ) -> Result<Select<'a, 'c>, ParseError<'b>> {
     Selectors::compile(selectors).map(|selectors| Select {
         document,
-        iter: document.elements.iter().zip(caches.iter_mut()),
+        caches,
+        iter: document.elements.iter(),
         selectors,
     })
 }
 
 /// An element iterator adaptor that yields elements matching given selectors.
 pub(crate) struct Select<'a, 'c> {
     document: &'a Document,
-    iter: Zip<std::slice::Iter<'a, NodeId>, std::slice::IterMut<'c, NthIndexCache>>,
+    caches: &'c mut NthIndexCache,
+    iter: std::slice::Iter<'a, NodeId>,
     /// The selectors to be matched.
     selectors: Selectors,
 }
@@ -43,13 +44,13 @@ impl<'a> Iterator for Select<'a, '_> {
 
     #[inline]
     fn next(&mut self) -> Option<Element<'a>> {
-        for (element_id, cache) in self.iter.by_ref() {
+        for element_id in self.iter.by_ref() {
             let NodeData::Element { element, .. } = &self.document[*element_id].data else {
                 unreachable!("Element ids always point to element nodes")
             };
             let element = Element::new(self.document, *element_id, element);
             for selector in self.selectors.iter() {
-                if element.matches(selector, cache) {
+                if element.matches(selector, self.caches) {
                     return Some(element);
                 }
             }

css-inline/src/lib.rs

@@ -37,6 +37,7 @@ pub use error::InlineError;
 use indexmap::IndexMap;
 #[cfg(feature = "stylesheet-cache")]
 use lru::{DefaultHasher, LruCache};
+use selectors::NthIndexCache;
 use std::{borrow::Cow, fmt::Formatter, hash::BuildHasherDefault, io::Write, sync::Arc};
 
 use crate::html::ElementStyleMap;
@@ -439,7 +440,8 @@ impl<'a> CSSInliner<'a> {
         {
             rule_list.push(rule);
         }
-        let mut caches = document.build_caches();
+        // This cache is unused but required in the `selectors` API
+        let mut caches = NthIndexCache::default();
         for (selectors, (start, end)) in &rule_list {
             // Only CSS Syntax Level 3 is supported, therefore it is OK to split by `,`
             // With `is` or `where` selectors (Level 4) this split should be done on the parser level