From e5d62e9915dfe62708e4996768dba989255e1b46 Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Thu, 24 Apr 2025 12:36:54 +0200
Subject: [PATCH] LibWeb: Track whether HTMLLinkElement was enabled when
 created by parser

This information is needed by the script-blocking style sheet logic, and
its absence was causing a WPT test to crash.
---
 Libraries/LibWeb/HTML/HTMLLinkElement.cpp     |  4 +--
 Libraries/LibWeb/HTML/HTMLLinkElement.h       |  3 ++
 Libraries/LibWeb/HTML/Parser/HTMLParser.cpp   |  4 ++-
 .../cssom/HTMLLinkElement-disabled-003.txt    |  6 ++++
 .../cssom/HTMLLinkElement-disabled-003.html   | 31 +++++++++++++++++++
 5 files changed, 45 insertions(+), 3 deletions(-)
 create mode 100644 Tests/LibWeb/Text/expected/wpt-import/css/cssom/HTMLLinkElement-disabled-003.txt
 create mode 100644 Tests/LibWeb/Text/input/wpt-import/css/cssom/HTMLLinkElement-disabled-003.html

diff --git a/Libraries/LibWeb/HTML/HTMLLinkElement.cpp b/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
index 2901f885ce1..9e36d6a3c47 100644
--- a/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
+++ b/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
@@ -696,8 +696,8 @@ bool HTMLLinkElement::contributes_a_script_blocking_style_sheet() const
 
     // FIXME: el's media attribute's value matches the environment.
 
-    // FIXME: el's style sheet was enabled when the element was created by the parser.
-    if (has_attribute(AttributeNames::disabled))
+    // el's style sheet was enabled when the element was created by the parser.
+    if (!m_was_enabled_when_created_by_parser)
         return false;
 
     // FIXME: The last time the event loop reached step 1, el's root was that Document.
diff --git a/Libraries/LibWeb/HTML/HTMLLinkElement.h b/Libraries/LibWeb/HTML/HTMLLinkElement.h
index dd0678a06c6..8c12a30d3ab 100644
--- a/Libraries/LibWeb/HTML/HTMLLinkElement.h
+++ b/Libraries/LibWeb/HTML/HTMLLinkElement.h
@@ -44,6 +44,7 @@ public:
     static WebIDL::ExceptionOr<void> load_fallback_favicon_if_needed(GC::Ref<DOM::Document>);
 
     void set_parser_document(Badge<HTMLParser>, GC::Ref<DOM::Document>);
+    void set_was_enabled_when_created_by_parser(Badge<HTMLParser>, bool was_enabled_when_created_by_parser) { m_was_enabled_when_created_by_parser = was_enabled_when_created_by_parser; }
 
     void set_media(String);
     String media() const;
@@ -161,6 +162,8 @@ private:
     // https://html.spec.whatwg.org/multipage/semantics.html#explicitly-enabled
     bool m_explicitly_enabled { false };
 
+    bool m_was_enabled_when_created_by_parser { false };
+
     Optional<String> m_mime_type;
 
     WeakPtr<DOM::Document> m_parser_document;
diff --git a/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp b/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
index 73524c7b35c..cca09a2a3e2 100644
--- a/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
+++ b/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
@@ -810,7 +810,9 @@ GC::Ref<DOM::Element> HTMLParser::create_element_for(HTMLToken const& token, Opt
     // AD-HOC: Let <link> elements know which document they were originally parsed for.
     //         This is used for the render-blocking logic.
     if (local_name == HTML::TagNames::link && namespace_ == Namespace::HTML) {
-        as<HTMLLinkElement>(*element).set_parser_document({}, document);
+        auto& link_element = as<HTMLLinkElement>(*element);
+        link_element.set_parser_document({}, document);
+        link_element.set_was_enabled_when_created_by_parser({}, !token.has_attribute(HTML::AttributeNames::disabled));
     }
 
     // 10. Append each attribute in the given token to element.
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/cssom/HTMLLinkElement-disabled-003.txt b/Tests/LibWeb/Text/expected/wpt-import/css/cssom/HTMLLinkElement-disabled-003.txt
new file mode 100644
index 00000000000..83b29dec2aa
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/cssom/HTMLLinkElement-disabled-003.txt
@@ -0,0 +1,6 @@
+Harness status: OK
+
+Found 1 tests
+
+1 Pass
+Pass	HTMLLinkElement.disabled's explicitly enabled state persists when disconnected and connected again
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/cssom/HTMLLinkElement-disabled-003.html b/Tests/LibWeb/Text/input/wpt-import/css/cssom/HTMLLinkElement-disabled-003.html
new file mode 100644
index 00000000000..eea9203a0e1
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/cssom/HTMLLinkElement-disabled-003.html
@@ -0,0 +1,31 @@
+<!doctype html>
+<title>&lt;link disabled&gt;'s "explicitly enabled" state persists after getting disconnected from the tree</title>
+<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
+<link rel="author" title="Mozilla" href="https://mozilla.org">
+<link rel="help" href="https://html.spec.whatwg.org/#attr-link-disabled">
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<link title="alt" rel="alternate stylesheet" disabled href="data:text/css,html { background: green }">
+<script>
+function assert_applies(applies) {
+  (applies ? assert_equals : assert_not_equals)(getComputedStyle(document.documentElement).backgroundColor, "rgb(0, 128, 0)");
+}
+
+const link = document.querySelector("link[disabled]");
+async_test(function(t) {
+  assert_true(link.disabled);
+  link.disabled = false;
+  assert_false(link.disabled);
+  assert_true(!link.hasAttribute("disabled"));
+  link.remove();
+
+  link.onload = t.step_func_done(function() {
+    assert_equals(document.styleSheets.length, 1);
+    let sheet = document.styleSheets[0];
+    assert_equals(sheet.ownerNode, link);
+    assert_applies(true);
+  });
+
+  document.head.appendChild(link);
+}, "HTMLLinkElement.disabled's explicitly enabled state persists when disconnected and connected again");
+</script>