From 8cc596196035730a8b965e7310499bca8266814f Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Sat, 19 Apr 2025 20:39:20 -0400
Subject: [PATCH] tweak

---
 .../src/internal/client/reactivity/forks.js   |  2 +-
 .../src/internal/client/reactivity/sources.js |  2 +-
 packages/svelte/src/internal/client/render.js |  1 -
 .../svelte/src/internal/client/runtime.js     | 26 +++++++++----------
 4 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/packages/svelte/src/internal/client/reactivity/forks.js b/packages/svelte/src/internal/client/reactivity/forks.js
index 632361966e..73bcc17720 100644
--- a/packages/svelte/src/internal/client/reactivity/forks.js
+++ b/packages/svelte/src/internal/client/reactivity/forks.js
@@ -149,7 +149,7 @@ export class Fork {
 			}
 
 			active_fork = new Fork();
-			forks.add(active_fork); // TODO figure out where we remove this
+			forks.add(active_fork);
 		}
 
 		return active_fork;
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index 711a252a11..678c75934a 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -34,7 +34,7 @@ import * as e from '../errors.js';
 import { legacy_mode_flag, tracing_mode_flag } from '../../flags/index.js';
 import { get_stack } from '../dev/tracing.js';
 import { component_context, is_runes } from '../context.js';
-import { active_fork, Fork } from './forks.js';
+import { Fork } from './forks.js';
 import { proxy } from '../proxy.js';
 import { execute_derived } from './deriveds.js';
 
diff --git a/packages/svelte/src/internal/client/render.js b/packages/svelte/src/internal/client/render.js
index 404965d9ab..3256fe8274 100644
--- a/packages/svelte/src/internal/client/render.js
+++ b/packages/svelte/src/internal/client/render.js
@@ -30,7 +30,6 @@ import * as w from './warnings.js';
 import * as e from './errors.js';
 import { assign_nodes } from './dom/template.js';
 import { is_passive_event } from '../../utils.js';
-import { active_fork, Fork } from './reactivity/forks.js';
 
 /**
  * This is normally true — block effects should run their intro transitions —
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 6015c39a74..02ead17a94 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -683,11 +683,7 @@ function infinite_loop_guard() {
 
 function flush_queued_root_effects() {
 	var was_updating_effect = is_updating_effect;
-
-	// TODO it should be impossible to get here without an active fork
-	if (!active_fork && queued_root_effects.length > 0) {
-		console.trace('here');
-	}
+	var fork = /** @type {Fork} */ (active_fork);
 
 	try {
 		var flush_count = 0;
@@ -698,7 +694,7 @@ function flush_queued_root_effects() {
 				infinite_loop_guard();
 			}
 
-			var revert = active_fork?.apply();
+			var revert = fork.apply();
 
 			/** @type {Effect[]} */
 			var async_effects = [];
@@ -724,13 +720,13 @@ function flush_queued_root_effects() {
 				process_effects(root, async_effects, render_effects, effects);
 			}
 
-			if (async_effects.length === 0 && (active_fork === null || active_fork.pending === 0)) {
-				active_fork?.commit();
+			if (async_effects.length === 0 && fork.pending === 0) {
+				fork.commit();
 				flush_queued_effects(render_effects);
 				flush_queued_effects(effects);
 			}
 
-			revert?.();
+			revert();
 
 			for (const effect of async_effects) {
 				update_effect(effect);
@@ -795,11 +791,13 @@ export function schedule_effect(signal) {
 	if (!is_flushing) {
 		is_flushing = true;
 		queueMicrotask(() => {
+			if (active_fork === null) {
+				// a flushSync happened in the meantime
+				return;
+			}
+
 			flush_queued_root_effects();
 
-			// TODO this doesn't seem quite right — may run into
-			// interesting cases where there are multiple roots.
-			// it'll do for now though
 			if (active_fork?.pending === 0) {
 				active_fork.remove();
 			}
@@ -845,14 +843,14 @@ export function schedule_effect(signal) {
  */
 function process_effects(root, async_effects, render_effects, effects) {
 	var effect = root.first;
+	var fork = /** @type {Fork} */ (active_fork);
 
 	while (effect !== null) {
 		var flags = effect.f;
 		var is_branch = (flags & BRANCH_EFFECT) !== 0;
 		var is_skippable_branch = is_branch && (flags & CLEAN) !== 0;
 
-		var skip =
-			is_skippable_branch || (flags & INERT) !== 0 || active_fork?.skipped_effects.has(effect);
+		var skip = is_skippable_branch || (flags & INERT) !== 0 || fork.skipped_effects.has(effect);
 
 		if (!skip) {
 			if ((flags & EFFECT_ASYNC) !== 0) {