LibWeb: Traverse shadow-including subtree when adopting DOM nodes

This takes care of two FIXMEs and fixes an issue on Google Docs where
we'd mix boxes from different documents in the same layout tree.
(This happened because shadow trees remained attached to their old
document when their host was adopted.)

3 files changed, 24 insertions, 4 deletions

diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index f072283a75..46dd53bba0 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -1116,8 +1116,7 @@ void Document::adopt_node(Node& node)
         node.remove();
 
     if (&old_document != this) {
-        // FIXME: This should be shadow-including.
-        node.for_each_in_inclusive_subtree([&](auto& inclusive_descendant) {
+        node.for_each_shadow_including_descendant([&](auto& inclusive_descendant) {
             inclusive_descendant.set_document({}, *this);
             // FIXME: If inclusiveDescendant is an element, then set the node document of each attribute in inclusiveDescendant’s attribute list to document.
             return IterationDecision::Continue;
@@ -1127,8 +1126,7 @@ void Document::adopt_node(Node& node)
         //        enqueue a custom element callback reaction with inclusiveDescendant, callback name "adoptedCallback",
         //        and an argument list containing oldDocument and document.
 
-        // FIXME: This should be shadow-including.
-        node.for_each_in_inclusive_subtree([&](auto& inclusive_descendant) {
+        node.for_each_shadow_including_descendant([&](auto& inclusive_descendant) {
             inclusive_descendant.adopted_from(old_document);
             return IterationDecision::Continue;
         });
diff --git a/Userland/Libraries/LibWeb/DOM/Node.h b/Userland/Libraries/LibWeb/DOM/Node.h
index d30275ef5c..8cd3ffb2c9 100644
--- a/Userland/Libraries/LibWeb/DOM/Node.h
+++ b/Userland/Libraries/LibWeb/DOM/Node.h
@@ -231,6 +231,10 @@ public:
 
     void queue_mutation_record(FlyString const& type, String attribute_name, String attribute_namespace, String old_value, NonnullRefPtr<NodeList> added_nodes, NonnullRefPtr<NodeList> removed_nodes, Node* previous_sibling, Node* next_sibling);
 
+    // https://dom.spec.whatwg.org/#concept-shadow-including-descendant
+    template<typename Callback>
+    IterationDecision for_each_shadow_including_descendant(Callback);
+
 protected:
     Node(Document&, NodeType);
 
diff --git a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
index b4306c4461..ea561e7b4c 100644
--- a/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
+++ b/Userland/Libraries/LibWeb/DOM/ShadowRoot.h
@@ -45,4 +45,22 @@ private:
 template<>
 inline bool Node::fast_is<ShadowRoot>() const { return is_shadow_root(); }
 
+template<typename Callback>
+inline IterationDecision Node::for_each_shadow_including_descendant(Callback callback)
+{
+    if (callback(*this) == IterationDecision::Break)
+        return IterationDecision::Break;
+    for (auto* child = first_child(); child; child = child->next_sibling()) {
+        if (child->is_element()) {
+            if (RefPtr<ShadowRoot> shadow_root = static_cast<Element*>(child)->shadow_root()) {
+                if (shadow_root->for_each_shadow_including_descendant(callback) == IterationDecision::Break)
+                    return IterationDecision::Break;
+            }
+        }
+        if (child->for_each_shadow_including_descendant(callback) == IterationDecision::Break)
+            return IterationDecision::Break;
+    }
+    return IterationDecision::Continue;
+}
+
 }