From 1c7f2a9f09da9111b47aef628662a625cb69d53e Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Tue, 20 Jun 2017 11:57:41 -0700
Subject: [PATCH] Account for left-to-right rather than right-to-left
 precedence of classes in selector maps.

MozReview-Commit-ID: 8qIl4k3RxaC
---
 components/style/selector_map.rs | 17 ++++++++---------
 tests/unit/style/stylist.rs      |  6 +++---
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/components/style/selector_map.rs b/components/style/selector_map.rs
index 48d25231b25d..77052990edc1 100644
--- a/components/style/selector_map.rs
+++ b/components/style/selector_map.rs
@@ -369,15 +369,12 @@ impl<T: SelectorMapEntry> SelectorMap<T> {
     }
 }
 
-/// Searches the selector from right to left, beginning to the left of the
-/// ::pseudo-element (if any), and ending at the first combinator.
+/// Searches a compound selector from left to right. If the compound selector
+/// is a pseudo-element, it's ignored.
 ///
 /// The first non-None value returned from |f| is returned.
-///
-/// Effectively, pseudo-elements are ignored, given only state pseudo-classes
-/// may appear before them.
 #[inline(always)]
-fn find_from_right<F, R>(mut iter: SelectorIter<SelectorImpl>,
+fn find_from_left<F, R>(mut iter: SelectorIter<SelectorImpl>,
                          mut f: F)
                          -> Option<R>
     where F: FnMut(&Component<SelectorImpl>) -> Option<R>,
@@ -388,6 +385,8 @@ fn find_from_right<F, R>(mut iter: SelectorIter<SelectorImpl>,
         }
     }
 
+    // Effectively, pseudo-elements are ignored, given only state pseudo-classes
+    // may appear before them.
     if iter.next_sequence() == Some(Combinator::PseudoElement) {
         for ss in &mut iter {
             if let Some(r) = f(ss) {
@@ -403,7 +402,7 @@ fn find_from_right<F, R>(mut iter: SelectorIter<SelectorImpl>,
 #[inline(always)]
 pub fn get_id_name(iter: SelectorIter<SelectorImpl>)
                    -> Option<Atom> {
-    find_from_right(iter, |ss| {
+    find_from_left(iter, |ss| {
         // TODO(pradeep): Implement case-sensitivity based on the
         // document type and quirks mode.
         if let Component::ID(ref id) = *ss {
@@ -417,7 +416,7 @@ pub fn get_id_name(iter: SelectorIter<SelectorImpl>)
 #[inline(always)]
 pub fn get_class_name(iter: SelectorIter<SelectorImpl>)
                       -> Option<Atom> {
-    find_from_right(iter, |ss| {
+    find_from_left(iter, |ss| {
         // TODO(pradeep): Implement case-sensitivity based on the
         // document type and quirks mode.
         if let Component::Class(ref class) = *ss {
@@ -431,7 +430,7 @@ pub fn get_class_name(iter: SelectorIter<SelectorImpl>)
 #[inline(always)]
 pub fn get_local_name(iter: SelectorIter<SelectorImpl>)
                       -> Option<LocalNameSelector<SelectorImpl>> {
-    find_from_right(iter, |ss| {
+    find_from_left(iter, |ss| {
         if let Component::LocalName(ref n) = *ss {
             return Some(LocalNameSelector {
                 name: n.name.clone(),
diff --git a/tests/unit/style/stylist.rs b/tests/unit/style/stylist.rs
index 1a28e5ea772b..0f371967efb6 100644
--- a/tests/unit/style/stylist.rs
+++ b/tests/unit/style/stylist.rs
@@ -194,7 +194,7 @@ fn test_get_id_name() {
 #[test]
 fn test_get_class_name() {
     let (rules_list, _) = get_mock_rules(&[".intro.foo", "#top"]);
-    assert_eq!(selector_map::get_class_name(rules_list[0][0].selector.iter()), Some(Atom::from("foo")));
+    assert_eq!(selector_map::get_class_name(rules_list[0][0].selector.iter()), Some(Atom::from("intro")));
     assert_eq!(selector_map::get_class_name(rules_list[1][0].selector.iter()), None);
 }
 
@@ -220,8 +220,8 @@ fn test_insert() {
     selector_map.insert(rules_list[1][0].clone(), QuirksMode::NoQuirks);
     assert_eq!(1, selector_map.id_hash.get(&Atom::from("top"), QuirksMode::NoQuirks).unwrap()[0].source_order);
     selector_map.insert(rules_list[0][0].clone(), QuirksMode::NoQuirks);
-    assert_eq!(0, selector_map.class_hash.get(&Atom::from("foo"), QuirksMode::NoQuirks).unwrap()[0].source_order);
-    assert!(selector_map.class_hash.get(&Atom::from("intro"), QuirksMode::NoQuirks).is_none());
+    assert_eq!(0, selector_map.class_hash.get(&Atom::from("intro"), QuirksMode::NoQuirks).unwrap()[0].source_order);
+    assert!(selector_map.class_hash.get(&Atom::from("foo"), QuirksMode::NoQuirks).is_none());
 }
 
 #[test]