feat: optimise jsx runtime (#4337)

* optimise jsx-runtime by only creating a new object when ref is passed

* add test

* shave

* Update jsx-runtime/src/index.js

Co-authored-by: Jason Miller <developit@users.noreply.github.com>

* fix

---------

Co-authored-by: Jason Miller <developit@users.noreply.github.com>

jsx-runtime/src/index.js

@@ -27,17 +27,22 @@ const isArray = Array.isArray;
  * @param {unknown} [__self]
  */
 function createVNode(type, props, key, isStaticChildren, __source, __self) {
+	if (!props) props = {};
 	// We'll want to preserve `ref` in props to get rid of the need for
 	// forwardRef components in the future, but that should happen via
 	// a separate PR.
-	let normalizedProps = {},
+	let normalizedProps = props,
 		ref,
 		i;
-	for (i in props) {
-		if (i == 'ref') {
-			ref = props[i];
-		} else {
-			normalizedProps[i] = props[i];
+
+	if ('ref' in normalizedProps) {
+		normalizedProps = {};
+		for (i in props) {
+			if (i == 'ref') {
+				ref = props[i];
+			} else {
+				normalizedProps[i] = props[i];
+			}
 		}
 	}
 

jsx-runtime/test/browser/jsx-runtime.test.js

@@ -34,8 +34,16 @@ describe('Babel jsx/jsxDEV', () => {
 
 	it('should keep ref in props', () => {
 		const ref = () => null;
-		const vnode = jsx('div', { ref });
+		const props = { ref };
+		const vnode = jsx('div', props);
 		expect(vnode.ref).to.equal(ref);
+		expect(vnode.props).to.not.equal(props);
+	});
+
+	it('should not copy props wen there is no ref in props', () => {
+		const props = { x: 'y' };
+		const vnode = jsx('div', props);
+		expect(vnode.props).to.equal(props);
 	});
 
 	it('should add keys', () => {