From 57e26ed6b9b2c0cf1e4f5ac3e85ca0c7f3647caa Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Sun, 22 Sep 2024 13:29:49 +0200
Subject: [PATCH] LibWeb: Abort ongoing fetch before starting a new link
 element fetch

If we decide to fetch another linked resource, we don't care about the
earlier fetch and can safely abort it.

This fixes an issue on GitHub where we'd load the same style sheet
multiple times and invalidate style for the entire document every time
it finished fetching.

By aborting the ongoing fetch, no excess invalidation happens.
---
 Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp | 6 +++++-
 Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h   | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
index 3d998776c96..9512c217490 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.cpp
@@ -19,6 +19,7 @@
 #include <LibWeb/DOM/ShadowRoot.h>
 #include <LibWeb/Fetch/Fetching/Fetching.h>
 #include <LibWeb/Fetch/Infrastructure/FetchAlgorithms.h>
+#include <LibWeb/Fetch/Infrastructure/FetchController.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Requests.h>
 #include <LibWeb/Fetch/Infrastructure/HTTP/Responses.h>
 #include <LibWeb/HTML/EventNames.h>
@@ -364,7 +365,9 @@ void HTMLLinkElement::default_fetch_and_process_linked_resource()
         process_linked_resource(success, response, body_bytes);
     };
 
-    Fetch::Fetching::fetch(realm(), *request, Fetch::Infrastructure::FetchAlgorithms::create(vm(), move(fetch_algorithms_input))).release_value_but_fixme_should_propagate_errors();
+    if (m_fetch_controller)
+        m_fetch_controller->abort(realm(), {});
+    m_fetch_controller = MUST(Fetch::Fetching::fetch(realm(), *request, Fetch::Infrastructure::FetchAlgorithms::create(vm(), move(fetch_algorithms_input))));
 }
 
 // https://html.spec.whatwg.org/multipage/links.html#link-type-stylesheet:process-the-linked-resource
@@ -610,6 +613,7 @@ WebIDL::ExceptionOr<void> HTMLLinkElement::load_fallback_favicon_if_needed(JS::N
 void HTMLLinkElement::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);
+    visitor.visit(m_fetch_controller);
     visitor.visit(m_loaded_style_sheet);
     visitor.visit(m_rel_list);
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h
index b2c50a1625d..0b6d69f3869 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLLinkElement.h
@@ -140,6 +140,8 @@ private:
         };
     };
 
+    JS::GCPtr<Fetch::Infrastructure::FetchController> m_fetch_controller;
+
     JS::GCPtr<CSS::CSSStyleSheet> m_loaded_style_sheet;
 
     Optional<DOM::DocumentLoadEventDelayer> m_document_load_event_delayer;