Add getContainerVNode getter

shared-internals/src/index.d.ts

@@ -7,6 +7,9 @@ export function getChildren(
 	vnode: preact.VNode
 ): Array<preact.VNode | null | undefined>;
 export function getComponentVNode(component: preact.Component): preact.VNode;
+export function getContainerVNode(
+	container: Element | Document | ShadowRoot | DocumentFragment
+): preact.VNode | null;
 
 //
 // Option hooks

shared-internals/src/index.js

@@ -48,6 +48,17 @@ export function getComponentVNode(component) {
 	return component._vnode;
 }
 
+/**
+ * Return the `VNode` that is associated with a DOM node that was rendered into.
+ * This property only exists on root nodes, commonly called containers. They
+ * are created via top-level `render(vnode, container)` calls.
+ * @param {Element | Document | ShadowRoot | DocumentFragment} container
+ * @returns {import('../../src/internal').VNode | null}
+ */
+export function getContainerVNode(container) {
+	return container._children;
+}
+
 // Options getters/setters
 
 /**

shared-internals/test/browser/internals.test.js

@@ -1,11 +1,19 @@
-import { createElement, render, Component, createRef, options } from 'preact';
+import {
+	createElement,
+	render,
+	Component,
+	createRef,
+	options,
+	Fragment
+} from 'preact';
 import { setupScratch, teardown } from '../../../test/_util/helpers';
 import {
 	getParent,
 	getComponent,
 	getDom,
 	getChildren,
 	getComponentVNode,
+	getContainerVNode,
 	getOptionsDiff,
 	getOptionsCommit,
 	getOptionsRoot,
@@ -109,6 +117,17 @@ describe('shared-internals', () => {
 		});
 	});
 
+	describe('getContainerVNode', () => {
+		it('should return undefined', () => {
+			expect(getContainerVNode(scratch)).to.equal(undefined);
+		});
+
+		it('should return root Fragment vnode', () => {
+			render(<div />, scratch);
+			expect(getContainerVNode(scratch).type).to.equal(Fragment);
+		});
+	});
+
 	describe('options', () => {
 		let prevDiff;
 		let prevCommit;