Fix rare scenario where an unmounted suspended tree would resolve

Author: JoviDeCroock

compat/src/suspense.js

@@ -180,7 +180,7 @@ Suspense.prototype._childDidSuspend = function (promise, suspendingVNode) {
 };
 
 Suspense.prototype.componentWillUnmount = function () {
-	this._suspenders = [];
+	this._suspenders = this.state._suspended = this._detachOnNextRender = null;
 };
 
 /**

compat/test/browser/suspense.test.js

@@ -415,6 +415,51 @@ describe('suspense', () => {
 		});
 	});
 
+	it('should crash when suspended child updates after unmount', () => {
+		/** @type {Component | null} */
+		let childInstance = null;
+		const neverResolvingPromise = new Promise(() => {});
+
+		class ThrowingChild extends Component {
+			constructor(props) {
+				super(props);
+				this.state = { suspend: false, value: 0 };
+				childInstance = this;
+			}
+
+			render(props, state) {
+				if (state.suspend) {
+					throw neverResolvingPromise;
+				}
+
+				return <div>value:{state.value}</div>;
+			}
+		}
+
+		render(
+			<Suspense fallback={<div>Suspended...</div>}>
+				<ThrowingChild />
+			</Suspense>,
+			scratch
+		);
+
+		expect(childInstance).to.not.equal(null);
+		expect(scratch.innerHTML).to.equal('<div>value:0</div>');
+
+		act(() => childInstance.setState({ suspend: true }));
+		rerender();
+		expect(scratch.innerHTML).to.equal('<div>Suspended...</div>');
+
+		render(null, scratch);
+
+		const rerenderDetachedChild = () => {
+			childInstance.setState({ value: 1, suspend: false });
+			rerender();
+		};
+
+		expect(rerenderDetachedChild).to.not.throw();
+	});
+
 	it('should properly call lifecycle methods of an initially suspending component', () => {
 		/** @type {() => Promise<void>} */
 		let resolve;

src/component.js

@@ -126,7 +126,7 @@ function renderComponent(component) {
 		commitQueue = [],
 		refQueue = [];
 
-	if (component._parentDom) {
+	if (component._parentDom && oldVNode._parent) {
 		const newVNode = assign({}, oldVNode);
 		newVNode._original = oldVNode._original + 1;
 		if (options.vnode) options.vnode(newVNode);