LibWeb: Add implementation of Node.compareDocumentPosition()

While looking into getting Duck Duck Go loading further in the
Browser, I noticed that it was complaining about the missing
method Node.compareDocumentPosition.

This change implements as much of the DOM spec as possible
with the current implementation of the DOM to date. The
implementation is validated by new tests in the Node.js.

1 files changed, 23 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Tests/DOM/Node.js b/Userland/Libraries/LibWeb/Tests/DOM/Node.js
index 47c3e1c668..38618c0dd9 100644
--- a/Userland/Libraries/LibWeb/Tests/DOM/Node.js
+++ b/Userland/Libraries/LibWeb/Tests/DOM/Node.js
@@ -36,4 +36,27 @@ afterInitialPageLoad(() => {
         document.body.removeChild(element);
         expect(element.isConnected).toBeFalse();
     });
+
+    test("Node.compareDocumentPosition()", () => {
+        const head = document.head;
+        const body = document.body;
+
+        expect(head.compareDocumentPosition(head)).toBe(0);
+
+        // FIXME: Can be uncommented once the IDL parser correctly implements nullable paramaters.
+        // expect(head.compareDocumentPosition(null) & Node.DOCUMENT_POSITION_DISCONNECTED | Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC).
+        //    toBe(Node.DOCUMENT_POSITION_DISCONNECTED | Node.DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC);
+
+        expect(head.compareDocumentPosition(body)).toBe(Node.DOCUMENT_POSITION_FOLLOWING);
+        expect(body.compareDocumentPosition(head)).toBe(Node.DOCUMENT_POSITION_PRECEDING);
+
+        const source = document.getElementById("source");
+        expect(source.compareDocumentPosition(body)).toBe(
+            Node.DOCUMENT_POSITION_CONTAINS | Node.DOCUMENT_POSITION_PRECEDING
+        );
+        expect(body.compareDocumentPosition(source)).toBe(
+            Node.DOCUMENT_POSITION_CONTAINED_BY | Node.DOCUMENT_POSITION_FOLLOWING
+        );
+        expect(source.compareDocumentPosition(head)).toBe(Node.DOCUMENT_POSITION_PRECEDING);
+    });
 });