Normalize CompositionEvent listeners in preact/compat (#3430)

Co-authored-by: Jovi De Croock <decroockjovi@gmail.com>

Author: hpneo

compat/src/render.js

@@ -123,8 +123,7 @@ options.vnode = vnode => {
 			if (IS_DOM && i === 'children' && type === 'noscript') {
 				// Emulate React's behavior of not rendering the contents of noscript tags on the client.
 				continue;
-			}
-			else if (i === 'value' && 'defaultValue' in props && value == null) {
+			} else if (i === 'value' && 'defaultValue' in props && value == null) {
 				// Skip applying value if it is null/undefined and we already set
 				// a default value
 				continue;
@@ -154,7 +153,7 @@ options.vnode = vnode => {
 				i = 'onfocusin';
 			} else if (/^onblur$/i.test(i)) {
 				i = 'onfocusout';
-			} else if (/^on(Ani|Tra|Tou|BeforeInp)/.test(i)) {
+			} else if (/^on(Ani|Tra|Tou|BeforeInp|Compo)/.test(i)) {
 				i = i.toLowerCase();
 			} else if (nonCustomElement && CAMEL_PROPS.test(i)) {
 				i = i.replace(/[A-Z0-9]/, '-$&').toLowerCase();

compat/test/browser/events.test.js

@@ -275,4 +275,11 @@ describe('preact/compat events', () => {
 		scratch.firstChild.dispatchEvent(createEvent('beforeinput'));
 		expect(spy).to.be.calledOnce;
 	});
+
+	it('should normalize compositionstart event listener', () => {
+		let spy = sinon.spy();
+		render(<input onCompositionStart={spy} />, scratch);
+		scratch.firstChild.dispatchEvent(createEvent('compositionstart'));
+		expect(spy).to.be.calledOnce;
+	});
 });