[css-nesting] Make selectors dropped during forgiving parsing still

count towards nest-containment. Also add a test. We keep track of this using a simple boolean, and since we make CSSParser from scratch every time we start parsing a new top-level selector, we don't need to worry about resetting it. In line with CSSWG resolution at w3c/csswg-drafts#7972. Bug: 1095675 Change-Id: I869e6859e32284167ef4e1e8c60b64e770b9e945 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4200218 Reviewed-by: Rune Lillesveen <futhark@chromium.org> Commit-Queue: Steinar H Gunderson <sesse@chromium.org> Cr-Commit-Position: refs/heads/main@{#1098520}
chromium · Jan 30, 2023 · c0c2114 · c0c2114
1 parent 40c9879
commit c0c2114
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Showing 4 changed files with 58 additions and 1 deletion.
diff --git a/third_party/blink/renderer/core/css/parser/css_selector_parser.cc b/third_party/blink/renderer/core/css/parser/css_selector_parser.cc
@@ -413,6 +413,12 @@ CSSSelectorList* CSSSelectorParser::ConsumeForgivingComplexSelectorList(
         ConsumeComplexSelector(argument, /*in_nested_style_rule=*/false,
                                /*first_in_complex_selector_list=*/false);
     if (selector.empty() || failed_parsing_ || !argument.AtEnd()) {
+      for (const CSSParserToken& token : argument) {
+        if (token.GetType() == kDelimiterToken && token.Delimiter() == '&') {
+          dropped_nest_token_during_forgiving_parsing_ = true;
+          break;
+        }
+      }
       if (in_supports_parsing_) {
         at_supports_drop_invalid_counter.Count();
       }
@@ -766,7 +772,8 @@ base::span<CSSSelector> CSSSelectorParser::ConsumeComplexSelector(
     // of SelectorListIsNestContaining().
     wtf_size_t last_index = output_.size() - 1;
     output_[last_index].SetLastInSelectorList(true);
-    if (!SelectorListIsNestContaining(reset_vector.AddedElements().data())) {
+    if (!dropped_nest_token_during_forgiving_parsing_ &&
+        !SelectorListIsNestContaining(reset_vector.AddedElements().data())) {
       output_.back().SetRelation(CSSSelector::kDescendant);
       output_.push_back(
           CSSSelector(parent_rule_for_nesting_, /*is_implicit=*/true));

diff --git a/third_party/blink/renderer/core/css/parser/css_selector_parser.h b/third_party/blink/renderer/core/css/parser/css_selector_parser.h
@@ -209,6 +209,11 @@ class CORE_EXPORT CSSSelectorParser {
   // PseudoType of the pseudo-element causing the restriction.
   CSSSelector::PseudoType restricting_pseudo_element_ =
       CSSSelector::kPseudoUnknown;
+  // Whether at any point we dropped an & token during forgiving parsing
+  // (e.g. in :is(!&, .foo)); such selectors are still considered as
+  // nest-containing. Since every top-level selector gets a new CSSParser
+  // instance, we don't need to worry about resetting it.
+  bool dropped_nest_token_during_forgiving_parsing_ = false;
   // If we're _resisting_ the default namespace, it means that we are inside
   // a nested selector (:is(), :where(), etc) where we should _consider_
   // ignoring the default namespace (depending on circumstance). See the

diff --git a/third_party/blink/web_tests/external/wpt/css/css-nesting/nest-containing-forgiving-ref.html b/third_party/blink/web_tests/external/wpt/css/css-nesting/nest-containing-forgiving-ref.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<title>Nest-containing in forgiving parsing</title>
+<style>
+  .test {
+    background-color: green;
+    width: 100px;
+    height: 100px;
+    display: grid;
+  }
+
+  body * + * {
+    margin-top: 8px;
+  }
+</style>
+<body>
+  <p>Tests pass if <strong>block is green</strong></p>
+  <div class="test"></div>
+</body>
diff --git a/third_party/blink/web_tests/external/wpt/css/css-nesting/nest-containing-forgiving.html b/third_party/blink/web_tests/external/wpt/css/css-nesting/nest-containing-forgiving.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<title>Nest-containing in forgiving parsing</title>
+<link rel="author" title="Steinar H. Gunderson" href="mailto:sesse@chromium.org">
+<link rel="help" href="https://drafts.csswg.org/css-nesting-1/">
+<link rel="match" href="nest-containing-forgiving-ref.html">
+<style>
+  .test {
+    background-color: red;
+    width: 100px;
+    height: 100px;
+    display: grid;
+  }
+
+  .does-not-exist {
+    :is(.test-1, !&) {
+      background-color: green;
+    }
+  }
+
+  body * + * {
+    margin-top: 8px;
+  }
+</style>
+<body>
+  <p>Tests pass if <strong>block is green</strong></p>
+  <div class="test test-1"></div>
+</body>