From e4d97add3da0de8d75ddbcd1950420f33ee03904 Mon Sep 17 00:00:00 2001
From: Luke Wilde <lukew@serenityos.org>
Date: Mon, 13 Sep 2021 23:01:17 +0100
Subject: [PATCH] LibWeb: Implement ParentNode.children

Required by Web Platform Tests for the innerHTML/outerHTML tests.
---
 Userland/Libraries/LibWeb/DOM/Document.idl         |  2 ++
 Userland/Libraries/LibWeb/DOM/DocumentFragment.idl |  2 ++
 Userland/Libraries/LibWeb/DOM/Element.idl          |  2 ++
 Userland/Libraries/LibWeb/DOM/ParentNode.cpp       | 12 ++++++++++++
 Userland/Libraries/LibWeb/DOM/ParentNode.h         |  2 ++
 Userland/Libraries/LibWeb/TreeNode.h               |  9 +++++++++
 6 files changed, 29 insertions(+)

diff --git a/Userland/Libraries/LibWeb/DOM/Document.idl b/Userland/Libraries/LibWeb/DOM/Document.idl
index ef5cb53e28..66c6bf8766 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.idl
+++ b/Userland/Libraries/LibWeb/DOM/Document.idl
@@ -64,6 +64,8 @@ interface Document : Node {
     Element? querySelector(DOMString selectors);
     ArrayFromVector querySelectorAll(DOMString selectors);
 
+    [SameObject] readonly attribute HTMLCollection children;
+
     // FIXME: These should all come from a GlobalEventHandlers mixin
     attribute EventHandler onabort;
     attribute EventHandler onauxclick;
diff --git a/Userland/Libraries/LibWeb/DOM/DocumentFragment.idl b/Userland/Libraries/LibWeb/DOM/DocumentFragment.idl
index 55f336dda4..666f6007ec 100644
--- a/Userland/Libraries/LibWeb/DOM/DocumentFragment.idl
+++ b/Userland/Libraries/LibWeb/DOM/DocumentFragment.idl
@@ -12,4 +12,6 @@ interface DocumentFragment : Node {
     Element? querySelector(DOMString selectors);
     ArrayFromVector querySelectorAll(DOMString selectors);
 
+    [SameObject] readonly attribute HTMLCollection children;
+
 };
diff --git a/Userland/Libraries/LibWeb/DOM/Element.idl b/Userland/Libraries/LibWeb/DOM/Element.idl
index 031e8d94d4..e791e9a88d 100644
--- a/Userland/Libraries/LibWeb/DOM/Element.idl
+++ b/Userland/Libraries/LibWeb/DOM/Element.idl
@@ -31,4 +31,6 @@ interface Element : Node {
 
     Element? querySelector(DOMString selectors);
     ArrayFromVector querySelectorAll(DOMString selectors);
+
+    [SameObject] readonly attribute HTMLCollection children;
 };
diff --git a/Userland/Libraries/LibWeb/DOM/ParentNode.cpp b/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
index f2136a1662..a13f29f647 100644
--- a/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
+++ b/Userland/Libraries/LibWeb/DOM/ParentNode.cpp
@@ -6,6 +6,7 @@
 
 #include <LibWeb/CSS/Parser/Parser.h>
 #include <LibWeb/CSS/SelectorEngine.h>
+#include <LibWeb/DOM/HTMLCollection.h>
 #include <LibWeb/DOM/ParentNode.h>
 #include <LibWeb/Dump.h>
 
@@ -75,4 +76,15 @@ u32 ParentNode::child_element_count() const
     return count;
 }
 
+// https://dom.spec.whatwg.org/#dom-parentnode-children
+NonnullRefPtr<HTMLCollection> ParentNode::children()
+{
+    // The children getter steps are to return an HTMLCollection collection rooted at this matching only element children.
+    // FIXME: This should return the same HTMLCollection object every time,
+    //        but that would cause a reference cycle since HTMLCollection refs the root.
+    return HTMLCollection::create(*this, [this](Element const& element) {
+        return is_parent_of(element);
+    });
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/DOM/ParentNode.h b/Userland/Libraries/LibWeb/DOM/ParentNode.h
index d977cc8f7d..fbbe4e0c3d 100644
--- a/Userland/Libraries/LibWeb/DOM/ParentNode.h
+++ b/Userland/Libraries/LibWeb/DOM/ParentNode.h
@@ -25,6 +25,8 @@ public:
     ExceptionOr<RefPtr<Element>> query_selector(StringView);
     ExceptionOr<NonnullRefPtrVector<Element>> query_selector_all(StringView);
 
+    NonnullRefPtr<HTMLCollection> children();
+
 protected:
     ParentNode(Document& document, NodeType type)
         : Node(document, type)
diff --git a/Userland/Libraries/LibWeb/TreeNode.h b/Userland/Libraries/LibWeb/TreeNode.h
index 466e8ef517..1fd4ef135a 100644
--- a/Userland/Libraries/LibWeb/TreeNode.h
+++ b/Userland/Libraries/LibWeb/TreeNode.h
@@ -398,6 +398,15 @@ public:
         return nullptr;
     }
 
+    bool is_parent_of(T const& other) const
+    {
+        for (auto* child = first_child(); child; child = child->next_sibling()) {
+            if (&other == child)
+                return true;
+        }
+        return false;
+    }
+
     ~TreeNode()
     {
         VERIFY(!m_parent);