feat: untrack

packages/reactivity/__tests__/effect.spec.ts

@@ -27,6 +27,7 @@ import {
   pauseTracking,
   resetTracking,
   startBatch,
+  untrack,
 } from '../src/effect'
 
 describe('reactivity/effect', () => {
@@ -1182,6 +1183,17 @@ describe('reactivity/effect', () => {
     expect(spy2).toHaveBeenCalledTimes(2)
   })
 
+  it('should not track dependencies when using untrack', () => {
+    const value = ref(1)
+    let dummy
+    effect(() => {
+      dummy = untrack(() => value.value)
+    })
+    expect(dummy).toBe(1)
+    value.value = 2
+    expect(dummy).toBe(1)
+  })
+
   describe('dep unsubscribe', () => {
     function getSubCount(dep: Dep | undefined) {
       let count = 0

packages/reactivity/src/effect.ts

@@ -537,6 +537,15 @@ export function resetTracking(): void {
   shouldTrack = last === undefined ? true : last
 }
 
+export function untrack<T>(fn: () => T): T {
+  try {
+    pauseTracking()
+    return fn()
+  } finally {
+    resetTracking()
+  }
+}
+
 /**
  * Registers a cleanup function for the current active effect.
  * The cleanup function is called right before the next effect run, or when the