From 6df4e5f5e75d7d6d439d1365ed7bed4fd2a8a1da Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Tue, 12 Nov 2024 18:08:49 +0000
Subject: [PATCH] LibWeb: Actually traverse the shadow root of the inclusive
 descendant

Previously, the inclusive descendant, which is the node that
for_each_shadow_including_inclusive_descendant was called on, would not
have it's shadow root traversed if it had one.

This is because the shadow root traversal was in the `for` loop, which
begins with the node's first child. The fix here is to move the shadow
root traversal outside of the loop, and check if the current node is an
element instead.
---
 Libraries/LibWeb/DOM/ShadowRoot.h             | 34 ++++++++++++-------
 ...boundary-of-inserted-node-is-traversed.txt |  1 +
 ...oundary-of-inserted-node-is-traversed.html | 14 ++++++++
 3 files changed, 37 insertions(+), 12 deletions(-)
 create mode 100644 Tests/LibWeb/Text/expected/DOM/shadow-root-boundary-of-inserted-node-is-traversed.txt
 create mode 100644 Tests/LibWeb/Text/input/DOM/shadow-root-boundary-of-inserted-node-is-traversed.html

diff --git a/Libraries/LibWeb/DOM/ShadowRoot.h b/Libraries/LibWeb/DOM/ShadowRoot.h
index f1c5fa92fe0..dd73fef68f6 100644
--- a/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -97,21 +97,37 @@ private:
 template<>
 inline bool Node::fast_is<ShadowRoot>() const { return node_type() == to_underlying(NodeType::DOCUMENT_FRAGMENT_NODE) && is_shadow_root(); }
 
+// https://dom.spec.whatwg.org/#concept-shadow-including-tree-order
+// In shadow-including tree order is shadow-including preorder, depth-first traversal of a node tree.
+// Shadow-including preorder, depth-first traversal of a node tree tree is preorder, depth-first traversal
+// of tree, with for each shadow host encountered in tree, shadow-including preorder, depth-first traversal
+// of that element’s shadow root’s node tree just after it is encountered.
+
+// https://dom.spec.whatwg.org/#concept-shadow-including-descendant
+// An object A is a shadow-including descendant of an object B, if A is a descendant of B, or A’s root is a
+// shadow root and A’s root’s host is a shadow-including inclusive descendant of B.
+
+// https://dom.spec.whatwg.org/#concept-shadow-including-inclusive-descendant
+// A shadow-including inclusive descendant is an object or one of its shadow-including descendants.
+
 template<typename Callback>
 inline TraversalDecision Node::for_each_shadow_including_inclusive_descendant(Callback callback)
 {
     if (callback(*this) == TraversalDecision::Break)
         return TraversalDecision::Break;
-    for (auto* child = first_child(); child; child = child->next_sibling()) {
-        if (child->is_element()) {
-            if (auto shadow_root = static_cast<Element*>(child)->shadow_root()) {
-                if (shadow_root->for_each_shadow_including_inclusive_descendant(callback) == TraversalDecision::Break)
-                    return TraversalDecision::Break;
-            }
+
+    if (is_element()) {
+        if (auto shadow_root = static_cast<Element*>(this)->shadow_root()) {
+            if (shadow_root->for_each_shadow_including_inclusive_descendant(callback) == TraversalDecision::Break)
+                return TraversalDecision::Break;
         }
+    }
+
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
         if (child->for_each_shadow_including_inclusive_descendant(callback) == TraversalDecision::Break)
             return TraversalDecision::Break;
     }
+
     return TraversalDecision::Continue;
 }
 
@@ -119,12 +135,6 @@ template<typename Callback>
 inline TraversalDecision Node::for_each_shadow_including_descendant(Callback callback)
 {
     for (auto* child = first_child(); child; child = child->next_sibling()) {
-        if (child->is_element()) {
-            if (JS::GCPtr<ShadowRoot> shadow_root = static_cast<Element*>(child)->shadow_root()) {
-                if (shadow_root->for_each_shadow_including_inclusive_descendant(callback) == TraversalDecision::Break)
-                    return TraversalDecision::Break;
-            }
-        }
         if (child->for_each_shadow_including_inclusive_descendant(callback) == TraversalDecision::Break)
             return TraversalDecision::Break;
     }
diff --git a/Tests/LibWeb/Text/expected/DOM/shadow-root-boundary-of-inserted-node-is-traversed.txt b/Tests/LibWeb/Text/expected/DOM/shadow-root-boundary-of-inserted-node-is-traversed.txt
new file mode 100644
index 00000000000..2bfbd60d9c4
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/DOM/shadow-root-boundary-of-inserted-node-is-traversed.txt
@@ -0,0 +1 @@
+Hello from script in the shadow root of the just inserted div!
diff --git a/Tests/LibWeb/Text/input/DOM/shadow-root-boundary-of-inserted-node-is-traversed.html b/Tests/LibWeb/Text/input/DOM/shadow-root-boundary-of-inserted-node-is-traversed.html
new file mode 100644
index 00000000000..b545db3d620
--- /dev/null
+++ b/Tests/LibWeb/Text/input/DOM/shadow-root-boundary-of-inserted-node-is-traversed.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const div = document.createElement("div");
+        const shadowRoot = div.attachShadow({ mode: "closed" });
+
+        const script = document.createElement("script");
+        script.innerText = "println('Hello from script in the shadow root of the just inserted div!')";
+        shadowRoot.appendChild(script);
+
+        document.body.appendChild(div);
+    });
+</script>