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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/281700">281700</a></dd>
<dt>Author</dt> <dd>antti@apple.com</dd>
<dt>Date</dt> <dd>2021-08-27 10:12:41 -0700 (Fri, 27 Aug 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>REGRESSION (<a href="http://trac.webkit.org/projects/webkit/changeset/276882">r276882</a>): Shadow trees may use stale style information after inline stylesheet is mutated via CSSOM
https://bugs.webkit.org/show_bug.cgi?id=228917
rdar://81483998

Reviewed by Alan Bujtas.

Source/WebCore:

If a stylesheet in a shadow tree is mutated via CSSOM we fail to remove cached style resolver for the mutated sheet
and may end up with stale style.

Test: fast/shadow-dom/shadow-stylesheet-mutation.html

* style/StyleScope.cpp:
(WebCore::Style::Scope::unshareShadowTreeResolverBeforeMutation):

Remove an assert relevant to the previous call site only.

(WebCore::Style::Scope::scheduleUpdate):

Unshare shadow tree resolver immeditaly when stylesheet contents or interpretation changes.

LayoutTests:

Original reduction by Thomas Ladd.

* fast/shadow-dom/shadow-stylesheet-mutation-expected.html: Added.
* fast/shadow-dom/shadow-stylesheet-mutation.html: Added.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorestyleStyleScopecpp">trunk/Source/WebCore/style/StyleScope.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsfastshadowdomshadowstylesheetmutationexpectedhtml">trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation-expected.html</a></li>
<li><a href="#trunkLayoutTestsfastshadowdomshadowstylesheetmutationhtml">trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (281699 => 281700)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2021-08-27 17:02:23 UTC (rev 281699)
+++ trunk/LayoutTests/ChangeLog 2021-08-27 17:12:41 UTC (rev 281700)
</span><span class="lines">@@ -1,3 +1,16 @@
</span><ins>+2021-08-27  Antti Koivisto  <antti@apple.com>
+
+        REGRESSION (r276882): Shadow trees may use stale style information after inline stylesheet is mutated via CSSOM
+        https://bugs.webkit.org/show_bug.cgi?id=228917
+        rdar://81483998
+
+        Reviewed by Alan Bujtas.
+
+        Original reduction by Thomas Ladd.
+
+        * fast/shadow-dom/shadow-stylesheet-mutation-expected.html: Added.
+        * fast/shadow-dom/shadow-stylesheet-mutation.html: Added.
+
</ins><span class="cx"> 2021-08-27  Chris Dumez  <cdumez@apple.com>
</span><span class="cx"> 
</span><span class="cx">         REGRESSION (r281516): imported/w3c/web-platform-tests/IndexedDB/serialize-sharedarraybuffer-throws.https.html is failing
</span></span></pre></div>
<a id="trunkLayoutTestsfastshadowdomshadowstylesheetmutationexpectedhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation-expected.html (0 => 281700)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation-expected.html                               (rev 0)
+++ trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation-expected.html  2021-08-27 17:12:41 UTC (rev 281700)
</span><span class="lines">@@ -0,0 +1 @@
</span><ins>+<div style="color:green">This should be green</div>
</ins></span></pre></div>
<a id="trunkLayoutTestsfastshadowdomshadowstylesheetmutationhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation.html (0 => 281700)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation.html                                (rev 0)
+++ trunk/LayoutTests/fast/shadow-dom/shadow-stylesheet-mutation.html   2021-08-27 17:12:41 UTC (rev 281700)
</span><span class="lines">@@ -0,0 +1,9 @@
</span><ins>+<div id=host></div>
+<script>
+const shadow = host.attachShadow({ mode: "open" });
+shadow.innerHTML = `<style></style><div>This should be green</div>`;
+const style = shadow.querySelector("style");
+style.sheet.addRule("div", "color: red");
+host.offsetWidth;
+style.sheet.addRule("div", "color: green");
+</script>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (281699 => 281700)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2021-08-27 17:02:23 UTC (rev 281699)
+++ trunk/Source/WebCore/ChangeLog      2021-08-27 17:12:41 UTC (rev 281700)
</span><span class="lines">@@ -1,3 +1,25 @@
</span><ins>+2021-08-27  Antti Koivisto  <antti@apple.com>
+
+        REGRESSION (r276882): Shadow trees may use stale style information after inline stylesheet is mutated via CSSOM
+        https://bugs.webkit.org/show_bug.cgi?id=228917
+        rdar://81483998
+
+        Reviewed by Alan Bujtas.
+
+        If a stylesheet in a shadow tree is mutated via CSSOM we fail to remove cached style resolver for the mutated sheet
+        and may end up with stale style.
+
+        Test: fast/shadow-dom/shadow-stylesheet-mutation.html
+
+        * style/StyleScope.cpp:
+        (WebCore::Style::Scope::unshareShadowTreeResolverBeforeMutation):
+
+        Remove an assert relevant to the previous call site only.
+
+        (WebCore::Style::Scope::scheduleUpdate):
+
+        Unshare shadow tree resolver immeditaly when stylesheet contents or interpretation changes.
+
</ins><span class="cx"> 2021-08-27  Emilio Cobos Ãlvarez  <emilio@crisal.io>
</span><span class="cx"> 
</span><span class="cx">         Don't forget about the outer selector when matching ::slotted().
</span></span></pre></div>
<a id="trunkSourceWebCorestyleStyleScopecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/style/StyleScope.cpp (281699 => 281700)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/style/StyleScope.cpp        2021-08-27 17:02:23 UTC (rev 281699)
+++ trunk/Source/WebCore/style/StyleScope.cpp   2021-08-27 17:12:41 UTC (rev 281700)
</span><span class="lines">@@ -133,7 +133,6 @@
</span><span class="cx"> void Scope::unshareShadowTreeResolverBeforeMutation()
</span><span class="cx"> {
</span><span class="cx">     ASSERT(m_shadowRoot);
</span><del>-    ASSERT(!m_resolver->isSharedBetweenShadowTrees());
</del><span class="cx"> 
</span><span class="cx">     documentScope().m_sharedShadowTreeResolvers.remove(makeResolverSharingKey());
</span><span class="cx"> }
</span><span class="lines">@@ -631,8 +630,10 @@
</span><span class="cx"> {
</span><span class="cx">     if (update == UpdateType::ContentsOrInterpretation) {
</span><span class="cx">         // :host and ::slotted rules might go away.
</span><del>-        if (m_shadowRoot)
</del><ins>+        if (m_shadowRoot) {
</ins><span class="cx">             Invalidator::invalidateHostAndSlottedStyleIfNeeded(*m_shadowRoot);
</span><ins>+            unshareShadowTreeResolverBeforeMutation();
+        }
</ins><span class="cx">         // FIXME: Animation code may trigger resource load in middle of style recalc and that can add a rule to a content extension stylesheet.
</span><span class="cx">         //        Fix and remove isResolvingTreeStyle() test below, see https://bugs.webkit.org/show_bug.cgi?id=194335
</span><span class="cx">         // FIXME: The m_isUpdatingStyleResolver test is here because extension stylesheets can get us here from Resolver::appendAuthorStyleSheets.
</span></span></pre>
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