Support the template tag (#4639)

* Support the template tag

* Add test

* Types

* chore: simplify template check

* chore: instantiate template tag in test

---------

Co-authored-by: Marvin Hagemeister <[email protected]>

Author: JoviDeCroock

src/diff/index.js

@@ -525,7 +525,8 @@ function diffElementNodes(
 			if (oldHtml) dom.innerHTML = '';
 
 			diffChildren(
-				dom,
+				// @ts-expect-error
+				newVNode.type === 'template' ? dom.content : dom,
 				isArray(newChildren) ? newChildren : [newChildren],
 				newVNode,
 				oldVNode,

test/browser/render.test.js

@@ -92,6 +92,20 @@ describe('render()', () => {
 		});
 	}
 
+	it('should support the <template> tag', () => {
+		function App() {
+			return (
+				<template>
+					<h1>it works</h1>
+				</template>
+			);
+		}
+
+		render(<App />, scratch);
+		const clone = scratch.firstChild.content.cloneNode(true);
+		expect(clone.firstChild.outerHTML).to.eql('<h1>it works</h1>');
+	});
+
 	it('should not render when detecting JSON-injection', () => {
 		const vnode = JSON.parse('{"type":"span","children":"Malicious"}');
 		render(vnode, scratch);