fix(reactivity): pass oldValue in debug info when triggering refs (#8210)

fix vuejs/pinia#2061

packages/reactivity/__tests__/computed.spec.ts

@@ -258,7 +258,7 @@ describe('reactivity/computed', () => {
     ])
   })
 
-  it('debug: onTrigger', () => {
+  it('debug: onTrigger (reactive)', () => {
     let events: DebuggerEvent[] = []
     const onTrigger = vi.fn((e: DebuggerEvent) => {
       events.push(e)
@@ -618,4 +618,29 @@ describe('reactivity/computed', () => {
     expect(serializeInner(root)).toBe('Hello World World World World')
     expect(COMPUTED_SIDE_EFFECT_WARN).toHaveBeenWarned()
   })
+
+  it('debug: onTrigger (ref)', () => {
+    let events: DebuggerEvent[] = []
+    const onTrigger = vi.fn((e: DebuggerEvent) => {
+      events.push(e)
+    })
+    const obj = ref(1)
+    const c = computed(() => obj.value, { onTrigger })
+
+    // computed won't trigger compute until accessed
+    c.value
+
+    obj.value++
+
+    expect(c.value).toBe(2)
+    expect(onTrigger).toHaveBeenCalledTimes(1)
+    expect(events[0]).toEqual({
+      effect: c.effect,
+      target: toRaw(obj),
+      type: TriggerOpTypes.SET,
+      key: 'value',
+      oldValue: 1,
+      newValue: 2,
+    })
+  })
 })

packages/reactivity/src/ref.ts

@@ -69,6 +69,7 @@ export function triggerRefValue(
   ref: RefBase<any>,
   dirtyLevel: DirtyLevels = DirtyLevels.Dirty,
   newVal?: any,
+  oldVal?: any,
 ) {
   ref = toRaw(ref)
   const dep = ref.dep
@@ -82,6 +83,7 @@ export function triggerRefValue(
             type: TriggerOpTypes.SET,
             key: 'value',
             newValue: newVal,
+            oldValue: oldVal,
           }
         : void 0,
     )
@@ -177,9 +179,10 @@ class RefImpl<T> {
       this.__v_isShallow || isShallow(newVal) || isReadonly(newVal)
     newVal = useDirectValue ? newVal : toRaw(newVal)
     if (hasChanged(newVal, this._rawValue)) {
+      const oldVal = this._rawValue
       this._rawValue = newVal
       this._value = useDirectValue ? newVal : toReactive(newVal)
-      triggerRefValue(this, DirtyLevels.Dirty, newVal)
+      triggerRefValue(this, DirtyLevels.Dirty, newVal, oldVal)
     }
   }
 }