Bug 1959597 - Fix tab crash with details-content enabled; r=emilio

lukewarlow · mozilla@keithcirkel.co.uk · commit 108f33584d73 · 2025-06-18T19:29:18.000Z
This patch ensures that we don't try to share styles when there's a mismatch between the backing pseudo elements. This fixes a debug assert that's hit by the details element when ::details-content is enabled. Differential Revision: https://phabricator.services.mozilla.com/D254208
diff --git a/servo/components/style/sharing/mod.rs b/servo/components/style/sharing/mod.rs
@@ -809,6 +809,11 @@ impl<E: TElement> StyleSharingCache<E> {
             return None;
         }
 
+        if target.implemented_pseudo_element() != candidate.implemented_pseudo_element() {
+            trace!("Miss: Element backed pseudo-element");
+            return None;
+        }
+
         if target.element.shadow_root().is_some() {
             trace!("Miss: Shadow host");
             return None;
diff --git a/testing/web-platform/tests/html/rendering/the-details-element/details-crash.html b/testing/web-platform/tests/html/rendering/the-details-element/details-crash.html
@@ -0,0 +1,11 @@
+<!DOCTYPE HTML>
+<link rel="help" href="https://html.spec.whatwg.org/multipage/rendering.html#the-details-and-summary-elements">
+<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#details-content-pseudo">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1959597">
+
+<!-- This test passes if it does not crash. -->
+
+<style>
+  :is([open],) {}
+</style>
+<details open></details>
