From f6c6dde342641ce6fd13261d1b5834683442c87d Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <dg@domgan.com>
Date: Wed, 29 May 2024 14:56:00 +0100
Subject: [PATCH] optimization

---
 package.json                                    |  3 ---
 .../svelte/src/internal/client/constants.js     | 17 +++++++++--------
 packages/svelte/src/internal/client/runtime.js  | 14 ++++++++++++--
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/package.json b/package.json
index 0159474d3b..4f5a11143b 100644
--- a/package.json
+++ b/package.json
@@ -5,9 +5,6 @@
   "private": true,
   "type": "module",
   "license": "MIT",
-  "engines": {
-    "pnpm": "^9.0.0"
-  },
   "repository": {
     "type": "git",
     "url": "git+https://github.com/sveltejs/svelte.git"
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index d087948b5e..543f812e79 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -5,16 +5,17 @@ export const BLOCK_EFFECT = 1 << 4;
 export const BRANCH_EFFECT = 1 << 5;
 export const ROOT_EFFECT = 1 << 6;
 export const UNOWNED = 1 << 7;
-export const CLEAN = 1 << 8;
-export const DIRTY = 1 << 9;
-export const MAYBE_DIRTY = 1 << 10;
-export const INERT = 1 << 11;
-export const DESTROYED = 1 << 12;
-export const EFFECT_RAN = 1 << 13;
+export const DISCONNECTED = 1 << 8;
+export const CLEAN = 1 << 9;
+export const DIRTY = 1 << 10;
+export const MAYBE_DIRTY = 1 << 11;
+export const INERT = 1 << 12;
+export const DESTROYED = 1 << 13;
+export const EFFECT_RAN = 1 << 14;
 /** 'Transparent' effects do not create a transition boundary */
-export const EFFECT_TRANSPARENT = 1 << 14;
+export const EFFECT_TRANSPARENT = 1 << 15;
 /** 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 << 15;
+export const LEGACY_DERIVED_PROP = 1 << 16;
 
 export const STATE_SYMBOL = Symbol('$state');
 export const LOADING_ATTR_SYMBOL = Symbol('');
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 22d2e5306a..c3f5945a7a 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -16,7 +16,8 @@ import {
 	STATE_SYMBOL,
 	BLOCK_EFFECT,
 	ROOT_EFFECT,
-	LEGACY_DERIVED_PROP
+	LEGACY_DERIVED_PROP,
+	DISCONNECTED
 } from './constants.js';
 import { flush_tasks } from './dom/task.js';
 import { add_owner } from './dev/ownership.js';
@@ -197,6 +198,7 @@ export function check_dirtiness(reaction) {
 	if (is_dirty && !is_unowned) {
 		return true;
 	}
+	var is_disconnected = (reaction.f & DISCONNECTED) !== 0;
 
 	if ((flags & MAYBE_DIRTY) !== 0 || (is_dirty && is_unowned)) {
 		var dependencies = reaction.deps;
@@ -239,7 +241,7 @@ export function check_dirtiness(reaction) {
 				} else if ((reaction.f & DIRTY) !== 0) {
 					// `signal` might now be dirty, as a result of calling `check_dirtiness` and/or `update_derived`
 					return true;
-				} else if ((reaction.f & DERIVED) !== 0) {
+				} else if (is_disconnected) {
 					// It might be that the derived was was dereferenced from its dependencies but has now come alive again.
 					// In thise case, we need to re-attach it to the graph and mark it dirty if any of its dependencies have
 					// changed since.
@@ -261,6 +263,9 @@ export function check_dirtiness(reaction) {
 		if (!is_unowned) {
 			set_signal_status(reaction, CLEAN);
 		}
+		if (is_disconnected) {
+			reaction.f ^= DISCONNECTED;
+		}
 	}
 
 	return is_dirty;
@@ -441,6 +446,11 @@ function remove_reaction(signal, dependency) {
 	// allowing it to either reconnect in the future, or be GC'd by the VM.
 	if (reactions_length === 0 && (dependency.f & DERIVED) !== 0) {
 		set_signal_status(dependency, MAYBE_DIRTY);
+		// If we are working with a derived that is owned by an effect, then mark it as being
+		// disconnected.
+		if ((dependency.f & (UNOWNED | DISCONNECTED)) === 0) {
+			dependency.f ^= DISCONNECTED;
+		}
 		remove_reactions(/** @type {import('#client').Derived} **/ (dependency), 0);
 	}
 }