avoid eagerly trigger user effects or templates effects when suspended

packages/svelte/src/internal/client/constants.js

@@ -5,23 +5,26 @@ export const BLOCK_EFFECT = 1 << 4;
 export const BRANCH_EFFECT = 1 << 5;
 export const ROOT_EFFECT = 1 << 6;
 export const BOUNDARY_EFFECT = 1 << 7;
-export const UNOWNED = 1 << 8;
-export const DISCONNECTED = 1 << 9;
-export const CLEAN = 1 << 10;
-export const DIRTY = 1 << 11;
-export const MAYBE_DIRTY = 1 << 12;
-export const INERT = 1 << 13;
-export const DESTROYED = 1 << 14;
-export const EFFECT_RAN = 1 << 15;
+export const TEMPLATE_EFFECT = 1 << 8;
+export const UNOWNED = 1 << 9;
+export const DISCONNECTED = 1 << 10;
+export const CLEAN = 1 << 11;
+export const DIRTY = 1 << 12;
+export const MAYBE_DIRTY = 1 << 13;
+export const INERT = 1 << 14;
+export const DESTROYED = 1 << 15;
+export const EFFECT_RAN = 1 << 16;
 /** 'Transparent' effects do not create a transition boundary */
-export const EFFECT_TRANSPARENT = 1 << 16;
+export const EFFECT_TRANSPARENT = 1 << 17;
 /** Svelte 4 legacy mode props need to be handled with deriveds and be recognized elsewhere, hence the dedicated flag */
-export const LEGACY_DERIVED_PROP = 1 << 17;
-export const INSPECT_EFFECT = 1 << 18;
-export const HEAD_EFFECT = 1 << 19;
-export const EFFECT_HAS_DERIVED = 1 << 20;
+export const LEGACY_DERIVED_PROP = 1 << 18;
+export const INSPECT_EFFECT = 1 << 19;
+export const HEAD_EFFECT = 1 << 20;
+export const EFFECT_HAS_DERIVED = 1 << 21;
 
-export const REACTION_IS_UPDATING = 1 << 21;
+// Flags used for async
+export const IS_ASYNC = 1 << 22;
+export const REACTION_IS_UPDATING = 1 << 23;
 
 export const STATE_SYMBOL = Symbol('$state');
 export const STATE_SYMBOL_METADATA = Symbol('$state metadata');

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -6,6 +6,7 @@ import {
 	DESTROYED,
 	DIRTY,
 	EFFECT_HAS_DERIVED,
+	IS_ASYNC,
 	MAYBE_DIRTY,
 	UNOWNED
 } from '../constants.js';
@@ -158,7 +159,7 @@ export function async_derived(fn) {
 			// TODO we should probably null out active effect here,
 			// rather than inside `restore()`
 		}
-	}, EFFECT_HAS_DERIVED);
+	}, IS_ASYNC);
 
 	return promise.then(() => value);
 }

packages/svelte/src/internal/client/reactivity/effects.js

@@ -37,7 +37,9 @@ import {
 	HEAD_EFFECT,
 	MAYBE_DIRTY,
 	EFFECT_HAS_DERIVED,
-	BOUNDARY_EFFECT
+	BOUNDARY_EFFECT,
+	IS_ASYNC,
+	TEMPLATE_EFFECT
 } from '../constants.js';
 import { set } from './sources.js';
 import * as e from '../errors.js';
@@ -145,7 +147,7 @@ function create_effect(type, fn, sync, push = true) {
 		effect.first === null &&
 		effect.nodes_start === null &&
 		effect.teardown === null &&
-		(effect.f & (EFFECT_HAS_DERIVED | BOUNDARY_EFFECT)) === 0;
+		(effect.f & (EFFECT_HAS_DERIVED | BOUNDARY_EFFECT | IS_ASYNC)) === 0;
 
 	if (!inert && !is_root && push) {
 		if (parent_effect !== null) {
@@ -385,7 +387,7 @@ function create_template_effect(fn, deriveds) {
 		});
 	}
 
-	block(effect);
+	block(effect, TEMPLATE_EFFECT);
 }
 
 /**

packages/svelte/src/internal/client/runtime.js

@@ -26,7 +26,9 @@ import {
 	LEGACY_DERIVED_PROP,
 	DISCONNECTED,
 	BOUNDARY_EFFECT,
-	REACTION_IS_UPDATING
+	REACTION_IS_UPDATING,
+	IS_ASYNC,
+	TEMPLATE_EFFECT
 } from './constants.js';
 import {
 	flush_idle_tasks,
@@ -102,6 +104,7 @@ export function set_active_effect(effect) {
 /* @__PURE__ */
 setInterval(() => {
 	if (active_effect !== null || active_reaction !== null) {
+		// eslint-disable-next-line no-debugger
 		debugger;
 	}
 });
@@ -819,6 +822,7 @@ export function schedule_effect(signal) {
 function process_effects(effect, collected_effects) {
 	var current_effect = effect.first;
 	var effects = [];
+	var suspended = false;
 
 	main_loop: while (current_effect !== null) {
 		var flags = current_effect.f;
@@ -827,13 +831,25 @@ function process_effects(effect, collected_effects) {
 		var sibling = current_effect.next;
 
 		if (!is_skippable_branch && (flags & INERT) === 0) {
+			var skip_suspended =
+				suspended &&
+				(flags & BRANCH_EFFECT) === 0 &&
+				((flags & BLOCK_EFFECT) === 0 || (flags & TEMPLATE_EFFECT) !== 0);
+
 			if ((flags & RENDER_EFFECT) !== 0) {
 				if (is_branch) {
 					current_effect.f ^= CLEAN;
-				} else {
+				} else if (!skip_suspended) {
 					try {
+						var is_async_effect = (current_effect.f & IS_ASYNC) !== 0;
+
 						if (check_dirtiness(current_effect)) {
 							update_effect(current_effect);
+							if (!suspended && is_async_effect) {
+								suspended = true;
+							}
+						} else if (!suspended && is_async_effect && current_effect.deps === null) {
+							suspended = true;
 						}
 					} catch (error) {
 						handle_error(error, current_effect, null, current_effect.ctx);
@@ -846,7 +862,7 @@ function process_effects(effect, collected_effects) {
 					current_effect = child;
 					continue;
 				}
-			} else if ((flags & EFFECT) !== 0) {
+			} else if ((flags & EFFECT) !== 0 && !skip_suspended) {
 				effects.push(current_effect);
 			}
 		}
@@ -858,6 +874,10 @@ function process_effects(effect, collected_effects) {
 				if (effect === parent) {
 					break main_loop;
 				}
+				// TODO: we need to know that this boundary has a valid `pending`
+				if (suspended && (parent.f & BOUNDARY_EFFECT) !== 0) {
+					suspended = false;
+				}
 				var parent_sibling = parent.next;
 				if (parent_sibling !== null) {
 					current_effect = parent_sibling;

packages/svelte/tests/runtime-runes/samples/async-derived/_config.js

@@ -25,7 +25,6 @@ export default test({
 		await Promise.resolve();
 		await Promise.resolve();
 		await Promise.resolve();
-		await tick();
 		flushSync();
 		assert.htmlEqual(target.innerHTML, '<p>42</p>');
 
@@ -34,7 +33,6 @@ export default test({
 		await Promise.resolve();
 		await Promise.resolve();
 		await Promise.resolve();
-		await Promise.resolve();
 		await tick();
 		assert.htmlEqual(target.innerHTML, '<p>84</p>');
 
@@ -47,20 +45,18 @@ export default test({
 		await Promise.resolve();
 		await Promise.resolve();
 		await Promise.resolve();
-		await Promise.resolve();
 		await tick();
 		assert.htmlEqual(target.innerHTML, '<p>86</p>');
 
 		assert.deepEqual(logs, [
+			'outside boundary 1',
 			'$effect.pre 42 1',
 			'template 42 1',
 			'$effect 42 1',
-			'$effect.pre 42 2',
-			'template 42 2',
-			'$effect 42 2',
-			'$effect.pre 84 2',
-			'template 84 2',
-			'$effect 84 2',
+			'outside boundary 2',
+			'$effect.pre 84 2', // TODO: why is this observed during tests, but not during runtime?
+			'template 84 2', // TODO: why is this observed during tests, but not during runtime?
+			'$effect 84 2', // TODO: why is this observed during tests, but not during runtime?
 			'$effect.pre 86 2',
 			'template 86 2',
 			'$effect 86 2'

packages/svelte/tests/runtime-runes/samples/async-derived/main.svelte

@@ -11,3 +11,5 @@
 		<p>pending</p>
 	{/snippet}
 </svelte:boundary>
+
+{console.log(`outside boundary ${num}`)}