LibWeb: Show pseudo-elements in DOM whose parent has no other children

If a DOM node is an element with pseudo-elements, but it has no child
DOM nodes and is not a shadow host, then the code that serializes its
pseudo-elements would get skipped, making them not show up in the
inspector.

Userland/Libraries/LibWeb/DOM/Element.cpp

@@ -1141,6 +1141,17 @@ JS::GCPtr<Layout::NodeWithStyle> Element::get_pseudo_element_node(CSS::Selector:
     return nullptr;
 }
 
+bool Element::has_pseudo_elements() const
+{
+    if (m_pseudo_element_data) {
+        for (auto& pseudo_element : *m_pseudo_element_data) {
+            if (pseudo_element.layout_node)
+                return true;
+        }
+    }
+    return false;
+}
+
 void Element::clear_pseudo_element_nodes(Badge<Layout::TreeBuilder>)
 {
     if (m_pseudo_element_data) {

Userland/Libraries/LibWeb/DOM/Element.h

@@ -245,6 +245,7 @@ public:
 
     void set_pseudo_element_node(Badge<Layout::TreeBuilder>, CSS::Selector::PseudoElement::Type, JS::GCPtr<Layout::NodeWithStyle>);
     JS::GCPtr<Layout::NodeWithStyle> get_pseudo_element_node(CSS::Selector::PseudoElement::Type) const;
+    bool has_pseudo_elements() const;
     void clear_pseudo_element_nodes(Badge<Layout::TreeBuilder>);
     void serialize_pseudo_elements_as_json(JsonArraySerializer<StringBuilder>& children_array) const;
 

Userland/Libraries/LibWeb/DOM/Node.cpp

@@ -1362,7 +1362,10 @@ void Node::serialize_tree_as_json(JsonObjectSerializer<StringBuilder>& object) c
 
     MUST((object.add("visible"sv, !!layout_node())));
 
-    if (has_child_nodes() || (is_element() && static_cast<DOM::Element const*>(this)->is_shadow_host())) {
+    auto const* element = is_element() ? static_cast<DOM::Element const*>(this) : nullptr;
+
+    if (has_child_nodes()
+        || (element && (element->is_shadow_host() || element->has_pseudo_elements()))) {
         auto children = MUST(object.add_array("children"sv));
         auto add_child = [&children](DOM::Node const& child) {
             if (child.is_uninteresting_whitespace_node())
@@ -1374,9 +1377,7 @@ void Node::serialize_tree_as_json(JsonObjectSerializer<StringBuilder>& object) c
         };
         for_each_child(add_child);
 
-        if (is_element()) {
-            auto const* element = static_cast<DOM::Element const*>(this);
-
+        if (element) {
             // Pseudo-elements don't have DOM nodes,so we have to add them separately.
             element->serialize_pseudo_elements_as_json(children);