WIP class boundaries

packages/svelte/src/internal/client/dom/blocks/boundary.js

@@ -1,6 +1,6 @@
 /** @import { Effect, TemplateNode, } from '#client' */
 
-import { BOUNDARY_EFFECT, EFFECT_TRANSPARENT } from '#client/constants';
+import { BOUNDARY_EFFECT, EFFECT_PRESERVED, EFFECT_TRANSPARENT } from '#client/constants';
 import { component_context, set_component_context } from '../../context.js';
 import { invoke_error_boundary } from '../../error-handling.js';
 import { block, branch, destroy_effect, pause_effect } from '../../reactivity/effects.js';
@@ -18,70 +18,133 @@ import {
 	remove_nodes,
 	set_hydrate_node
 } from '../hydration.js';
+import { get_next_sibling } from '../operations.js';
 import { queue_micro_task } from '../task.js';
 
 /**
- * @param {Effect} boundary
- * @param {() => void} fn
+ * @typedef {{
+ * 	 onerror?: (error: unknown, reset: () => void) => void;
+ *   failed?: (anchor: Node, error: () => unknown, reset: () => () => void) => void;
+ * }} BoundaryProps
  */
-function with_boundary(boundary, fn) {
+
+var flags = EFFECT_TRANSPARENT | EFFECT_PRESERVED | BOUNDARY_EFFECT;
+
+/**
+ * @param {TemplateNode} node
+ * @param {BoundaryProps} props
+ * @param {((anchor: Node) => void)} children
+ * @returns {void}
+ */
+export function boundary(node, props, children) {
+	new Boundary(node, props, children);
+}
+
+export class Boundary {
+	/** @type {Boundary | null} */
+	parent;
+
+	/** @type {TemplateNode} */
+	#anchor;
+
+	/** @type {TemplateNode} */
+	#hydrate_open;
+
+	/** @type {BoundaryProps} */
+	#props;
+
+	/** @type {((anchor: Node) => void)} */
+	#children;
+
+	/** @type {Effect} */
+	#effect;
+
+	/** @type {Effect | null} */
+	#main_effect = null;
+
+	/** @type {Effect | null} */
+	#failed_effect = null;
+
+	#is_creating_fallback = false;
+
+	/**
+	 * @param {TemplateNode} node
+	 * @param {BoundaryProps} props
+	 * @param {((anchor: Node) => void)} children
+	 */
+	constructor(node, props, children) {
+		this.#anchor = node;
+		this.#props = props;
+		this.#children = children;
+
+		this.#hydrate_open = hydrate_node;
+
+		this.parent = /** @type {Effect} */ (active_effect).b;
+
+		this.#effect = block(() => {
+			/** @type {Effect} */ (active_effect).b = this;
+
+			if (hydrating) {
+				hydrate_next();
+			}
+
+			try {
+				this.#main_effect = branch(() => children(this.#anchor));
+			} catch (error) {
+				this.error(error);
+			}
+		}, flags);
+
+		if (hydrating) {
+			this.#anchor = hydrate_node;
+		}
+	}
+
+	/**
+	 * @param {() => Effect | null} fn
+	 */
+	#run(fn) {
 		var previous_effect = active_effect;
 		var previous_reaction = active_reaction;
 		var previous_ctx = component_context;
 
-	set_active_effect(boundary);
-	set_active_reaction(boundary);
-	set_component_context(boundary.ctx);
+		set_active_effect(this.#effect);
+		set_active_reaction(this.#effect);
+		set_component_context(this.#effect.ctx);
 
 		try {
-		fn();
+			return fn();
 		} finally {
 			set_active_effect(previous_effect);
 			set_active_reaction(previous_reaction);
 			set_component_context(previous_ctx);
 		}
-}
+	}
 
-/**
- * @param {TemplateNode} node
- * @param {{
- * 	 onerror?: (error: unknown, reset: () => void) => void,
- *   failed?: (anchor: Node, error: () => unknown, reset: () => () => void) => void
- * }} props
- * @param {((anchor: Node) => void)} boundary_fn
- * @returns {void}
- */
-export function boundary(node, props, boundary_fn) {
-	var anchor = node;
+	/** @param {unknown} error */
+	error(error) {
+		var onerror = this.#props.onerror;
+		let failed = this.#props.failed;
 
-	/** @type {Effect} */
-	var boundary_effect;
-
-	block(() => {
-		var boundary = /** @type {Effect} */ (active_effect);
-		var hydrate_open = hydrate_node;
-		var is_creating_fallback = false;
+		const reset = () => {
+			if (this.#failed_effect !== null) {
+				pause_effect(this.#failed_effect, () => {
+					this.#failed_effect = null;
+				});
+			}
 
-		// We re-use the effect's fn property to avoid allocation of an additional field
-		boundary.fn = (/** @type {unknown}} */ error) => {
-			var onerror = props.onerror;
-			let failed = props.failed;
+			this.#main_effect = this.#run(() => {
+				this.#is_creating_fallback = false;
+				return branch(() => this.#children(this.#anchor));
+			});
+		};
 
 		// If we have nothing to capture the error, or if we hit an error while
 		// rendering the fallback, re-throw for another boundary to handle
-			if ((!onerror && !failed) || is_creating_fallback) {
+		if (this.#is_creating_fallback || (!onerror && !failed)) {
 			throw error;
 		}
 
-			var reset = () => {
-				pause_effect(boundary_effect);
-
-				with_boundary(boundary, () => {
-					is_creating_fallback = false;
-					boundary_effect = branch(() => boundary_fn(anchor));
-				});
-			};
-
 		var previous_reaction = active_reaction;
 
 		try {
@@ -91,46 +154,61 @@ export function boundary(node, props, boundary_fn) {
 			set_active_reaction(previous_reaction);
 		}
 
-			if (boundary_effect) {
-				destroy_effect(boundary_effect);
-			} else if (hydrating) {
-				set_hydrate_node(hydrate_open);
+		if (this.#main_effect) {
+			destroy_effect(this.#main_effect);
+			this.#main_effect = null;
+		}
+
+		if (this.#failed_effect) {
+			destroy_effect(this.#failed_effect);
+			this.#failed_effect = null;
+		}
+
+		if (hydrating) {
+			set_hydrate_node(this.#hydrate_open);
 			next();
 			set_hydrate_node(remove_nodes());
 		}
 
 		if (failed) {
-				// Render the `failed` snippet in a microtask
 			queue_micro_task(() => {
-					with_boundary(boundary, () => {
-						is_creating_fallback = true;
+				this.#failed_effect = this.#run(() => {
+					this.#is_creating_fallback = true;
 
 					try {
-							boundary_effect = branch(() => {
+						return branch(() => {
 							failed(
-									anchor,
+								this.#anchor,
 								() => error,
 								() => reset
 							);
 						});
 					} catch (error) {
-							invoke_error_boundary(error, /** @type {Effect} */ (boundary.parent));
+						invoke_error_boundary(error, /** @type {Effect} */ (this.#effect.parent));
+						return null;
+					} finally {
+						this.#is_creating_fallback = false;
 					}
-
-						is_creating_fallback = false;
 				});
 			});
 		}
-		};
-
-		if (hydrating) {
-			hydrate_next();
 	}
+}
 
-		boundary_effect = branch(() => boundary_fn(anchor));
-	}, EFFECT_TRANSPARENT | BOUNDARY_EFFECT);
+/**
+ *
+ * @param {Effect} effect
+ * @param {DocumentFragment} fragment
+ */
+function move_effect(effect, fragment) {
+	var node = effect.nodes_start;
+	var end = effect.nodes_end;
 
-	if (hydrating) {
-		anchor = hydrate_node;
+	while (node !== null) {
+		/** @type {TemplateNode | null} */
+		var next = node === end ? null : /** @type {TemplateNode} */ (get_next_sibling(node));
+
+		fragment.append(node);
+		node = next;
 	}
 }