Remove _nextDom usage

jsx-runtime/src/index.js

@@ -50,7 +50,6 @@ function createVNode(type, props, key, isStaticChildren, __source, __self) {
 		_parent: null,
 		_depth: 0,
 		_dom: null,
-		_nextDom: undefined,
 		_component: null,
 		constructor: undefined,
 		_original: --vnodeId,

src/create-element.js

@@ -67,11 +67,6 @@ export function createVNode(type, props, key, ref, original) {
 		_parent: null,
 		_depth: 0,
 		_dom: null,
-		// _nextDom must be initialized to undefined b/c it will eventually
-		// be set to dom.nextSibling which can return `null` and it is important
-		// to be able to distinguish between an uninitialized _nextDom and
-		// a _nextDom that has been set to `null`
-		_nextDom: UNDEFINED,
 		_component: null,
 		constructor: UNDEFINED,
 		_original: original == null ? ++vnodeId : original,

src/diff/children.js

@@ -62,9 +62,12 @@ export function diffChildren(
 
 	let newChildrenLength = renderResult.length;
 
-	newParentVNode._nextDom = oldDom;
-	constructNewChildrenArray(newParentVNode, renderResult, oldChildren);
-	oldDom = newParentVNode._nextDom;
+	oldDom = constructNewChildrenArray(
+		newParentVNode,
+		renderResult,
+		oldChildren,
+		oldDom
+	);
 
 	for (i = 0; i < newChildrenLength; i++) {
 		childVNode = newParentVNode._children[i];
@@ -82,7 +85,7 @@ export function diffChildren(
 		childVNode._index = i;
 
 		// Morph the old element into the new one, but don't append it to the dom yet
-		diff(
+		let result = diff(
 			parentDom,
 			childVNode,
 			oldVNode,
@@ -117,49 +120,32 @@ export function diffChildren(
 			oldVNode._children === childVNode._children
 		) {
 			oldDom = insert(childVNode, oldDom, parentDom);
-		} else if (
-			typeof childVNode.type == 'function' &&
-			childVNode._nextDom !== UNDEFINED
-		) {
-			// Since Fragments or components that return Fragment like VNodes can
-			// contain multiple DOM nodes as the same level, continue the diff from
-			// the sibling of last DOM child of this child VNode
-			oldDom = childVNode._nextDom;
+		} else if (typeof childVNode.type == 'function' && result !== UNDEFINED) {
+			oldDom = result;
 		} else if (newDom) {
 			oldDom = newDom.nextSibling;
 		}
 
-		// Eagerly cleanup _nextDom. We don't need to persist the value because it
-		// is only used by `diffChildren` to determine where to resume the diff
-		// after diffing Components and Fragments. Once we store it the nextDOM
-		// local var, we can clean up the property. Also prevents us hanging on to
-		// DOM nodes that may have been unmounted.
-		childVNode._nextDom = UNDEFINED;
-
 		// Unset diffing flags
 		childVNode._flags &= ~(INSERT_VNODE | MATCHED);
 	}
 
-	// TODO: With new child diffing algo, consider alt ways to diff Fragments.
-	// Such as dropping oldDom and moving fragments in place
-	//
-	// Because the newParentVNode is Fragment-like, we need to set it's
-	// _nextDom property to the nextSibling of its last child DOM node.
-	//
-	// `oldDom` contains the correct value here because if the last child
-	// is a Fragment-like, then oldDom has already been set to that child's _nextDom.
-	// If the last child is a DOM VNode, then oldDom will be set to that DOM
-	// node's nextSibling.
-	newParentVNode._nextDom = oldDom;
 	newParentVNode._dom = firstChildDom;
+
+	return oldDom;
 }
 
 /**
  * @param {VNode} newParentVNode
  * @param {ComponentChildren[]} renderResult
  * @param {VNode[]} oldChildren
  */
-function constructNewChildrenArray(newParentVNode, renderResult, oldChildren) {
+function constructNewChildrenArray(
+	newParentVNode,
+	renderResult,
+	oldChildren,
+	oldDom
+) {
 	/** @type {number} */
 	let i;
 	/** @type {VNode} */
@@ -309,14 +295,16 @@ function constructNewChildrenArray(newParentVNode, renderResult, oldChildren) {
 		for (i = 0; i < oldChildrenLength; i++) {
 			oldVNode = oldChildren[i];
 			if (oldVNode != null && (oldVNode._flags & MATCHED) === 0) {
-				if (oldVNode._dom == newParentVNode._nextDom) {
-					newParentVNode._nextDom = getDomSibling(oldVNode);
+				if (oldVNode._dom == oldDom) {
+					oldDom = getDomSibling(oldVNode);
 				}
 
 				unmount(oldVNode, oldVNode);
 			}
 		}
 	}
+
+	return oldDom;
 }
 
 /**

src/diff/index.js

@@ -244,7 +244,7 @@ export function diff(
 				tmp != null && tmp.type === Fragment && tmp.key == null;
 			let renderResult = isTopLevelFragment ? tmp.props.children : tmp;
 
-			diffChildren(
+			oldDom = diffChildren(
 				parentDom,
 				isArray(renderResult) ? renderResult : [renderResult],
 				newVNode,
@@ -281,6 +281,7 @@ export function diff(
 				while (oldDom && oldDom.nodeType === 8 && oldDom.nextSibling) {
 					oldDom = oldDom.nextSibling;
 				}
+
 				excessDomChildren[excessDomChildren.indexOf(oldDom)] = null;
 				newVNode._dom = oldDom;
 			} else {
@@ -296,7 +297,7 @@ export function diff(
 		newVNode._children = oldVNode._children;
 		newVNode._dom = oldVNode._dom;
 	} else {
-		newVNode._dom = diffElementNodes(
+		oldDom = newVNode._dom = diffElementNodes(
 			oldVNode._dom,
 			newVNode,
 			oldVNode,
@@ -310,6 +311,8 @@ export function diff(
 	}
 
 	if ((tmp = options.diffed)) tmp(newVNode);
+
+	return newVNode._flags & MODE_SUSPENDED ? undefined : oldDom;
 }
 
 /**
@@ -318,8 +321,6 @@ export function diff(
  * @param {VNode} root
  */
 export function commitRoot(commitQueue, root, refQueue) {
-	root._nextDom = UNDEFINED;
-
 	for (let i = 0; i < refQueue.length; i++) {
 		applyRef(refQueue[i], refQueue[++i], refQueue[++i]);
 	}
@@ -632,9 +633,7 @@ export function unmount(vnode, parentVNode, skipRemove) {
 		removeNode(vnode._dom);
 	}
 
-	// Must be set to `undefined` to properly clean up `_nextDom`
-	// for which `null` is a valid value. See comment in `create-element.js`
-	vnode._component = vnode._parent = vnode._dom = vnode._nextDom = UNDEFINED;
+	vnode._component = vnode._parent = vnode._dom = UNDEFINED;
 }
 
 /** The `.render()` method for a PFC backing instance. */

src/internal.d.ts

@@ -150,10 +150,6 @@ declare global {
 		 * The [first (for Fragments)] DOM child of a VNode
 		 */
 		_dom: PreactElement | null;
-		/**
-		 * The last dom child of a Fragment, or components that return a Fragment
-		 */
-		_nextDom: PreactElement | null | undefined;
 		_component: Component | null;
 		constructor: undefined;
 		_original: number;