revised

Author: trueadm

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

@@ -418,8 +418,12 @@ export function update_reaction(reaction) {
 	skip_reaction =
 		(flags & UNOWNED) !== 0 &&
 		(!is_flushing_effect ||
+			// If we were previously not in a reactive context and we're reading an unowned derived
+			// that was created inside another derived, then we don't fully know the real owner and thus
+			// we need to skip adding any reactions for this unowned
+				((previous_reaction === null || previous_untracking) &&
 				(/** @type {Derived} */ (reaction).parent !== null &&
-				(/** @type {Derived} */ (reaction).parent.f & DERIVED) !== 0));
+				(/** @type {Derived} */ (reaction).parent.f & DERIVED) !== 0)));
 
 	derived_sources = null;
 	set_component_context(reaction.ctx);

packages/svelte/tests/signals/test.ts

@@ -69,7 +69,7 @@ describe('signals', () => {
 		};
 	});
 
-	test('multiple effects with state and derived in it#1', () => {
+	test('multiple effects with state and derived in it #1', () => {
 		const log: string[] = [];
 
 		let count = state(0);
@@ -90,7 +90,7 @@ describe('signals', () => {
 		};
 	});
 
-	test('multiple effects with state and derived in it#2', () => {
+	test('multiple effects with state and derived in it #2', () => {
 		const log: string[] = [];
 
 		let count = state(0);
@@ -596,6 +596,46 @@ describe('signals', () => {
 		};
 	});
 
+	test('mixed nested deriveds correctly cleanup when no longer connected to graph #3', () => {
+		let a: Derived<unknown>;
+		let b: Derived<unknown>;
+		let s = state(0);
+		let logs: any[] = [];
+
+		const destroy = effect_root(() => {
+			render_effect(() => {
+				a = derived(() => {
+					b = derived(() => {
+						return $.get(s);
+					});
+					effect_root(() => {
+						$.get(b);
+					});
+					render_effect(() => {
+						debugger
+						logs.push($.get(b));
+					});
+					$.get(s);
+				});
+				$.get(a);
+			});
+		});
+
+		return () => {
+			flushSync();
+			assert.equal(a?.deps?.length, 1);
+			assert.equal(s?.reactions?.length, 2);
+
+			set(s, 1);
+			flushSync();
+
+			assert.deepEqual(logs, [0, 1]);
+
+			destroy();
+			assert.equal(s?.reactions, null);
+		};
+	});
+
 	test('deriveds update upon reconnection #1', () => {
 		let a = state(false);
 		let b = state(false);