feat: add untrack, untrackScope (#25)

Author: johnsoncodehk

Diff for: src/effect.ts

@@ -5,6 +5,17 @@ export let activeSub: Subscriber | undefined;
 export let activeTrackId = 0;
 export let lastTrackId = 0;
 
+export function untrack<T>(fn: () => T): T {
+	const prevSub = activeSub;
+	const prevTrackId = activeTrackId;
+	setActiveSub(undefined, 0);
+	try {
+		return fn();
+	} finally {
+		setActiveSub(prevSub, prevTrackId);
+	}
+}
+
 export function setActiveSub(sub: Subscriber | undefined, trackId: number): void {
 	activeSub = sub;
 	activeTrackId = trackId;

Diff for: src/effectScope.ts

@@ -4,6 +4,22 @@ import { endTrack, Link, startTrack, Subscriber, SubscriberFlags } from './syste
 export let activeEffectScope: EffectScope | undefined = undefined;
 export let activeScopeTrackId = 0;
 
+export function untrackScope<T>(fn: () => T): T {
+	const prevSub = activeEffectScope;
+	const prevTrackId = activeScopeTrackId;
+	setActiveScope(undefined, 0);
+	try {
+		return fn();
+	} finally {
+		setActiveScope(prevSub, prevTrackId);
+	}
+}
+
+export function setActiveScope(sub: EffectScope | undefined, trackId: number): void {
+	activeEffectScope = sub;
+	activeScopeTrackId = trackId;
+}
+
 export function effectScope(): EffectScope {
 	return new EffectScope();
 }
@@ -34,13 +50,11 @@ export class EffectScope implements Subscriber {
 	run<T>(fn: () => T): T {
 		const prevSub = activeEffectScope;
 		const prevTrackId = activeScopeTrackId;
-		activeEffectScope = this;
-		activeScopeTrackId = this.trackId;
+		setActiveScope(this, this.trackId);
 		try {
 			return fn();
 		} finally {
-			activeEffectScope = prevSub;
-			activeScopeTrackId = prevTrackId;
+			setActiveScope(prevSub, prevTrackId);
 		}
 	}
 

Diff for: tests/untrack.spec.ts

@@ -0,0 +1,12 @@
+import { untrack } from '../src';
+import { signal, computed } from './api';
+import { expect, test } from 'vitest';
+
+test('should untrack', () => {
+	const src = signal(0);
+	const c = computed(() => untrack(() => src.get()));
+	expect(c.get()).toBe(0);
+
+	src.set(1);
+	expect(c.get()).toBe(0);
+});