feat(reactivity): add Vue.delete workaround (#571)

README.md

@@ -200,10 +200,14 @@ a.list[1].count === 1 // true
 
 <details>
 <summary>
-⚠️ <code>set</code> workaround for adding new reactive properties
+⚠️ <code>set</code> and <code>del</code> workaround for adding and deleting reactive properties
 </summary>
 
-> ⚠️ Warning: `set` does NOT exist in Vue 3. We provide it as a workaround here, due to the limitation of [Vue 2.x reactivity system](https://vuejs.org/v2/guide/reactivity.html#For-Objects). In Vue 2, you will need to call `set` to track new keys on an `object`(similar to `Vue.set` but for `reactive objects` created by the Composition API). In Vue 3, you can just assign them like normal objects.
+> ⚠️ Warning: `set` and `del` do NOT exist in Vue 3. We provide them as a workaround here, due to the limitation of [Vue 2.x reactivity system](https://vuejs.org/v2/guide/reactivity.html#For-Objects).
+>
+> In Vue 2, you will need to call `set` to track new keys on an `object`(similar to `Vue.set` but for `reactive objects` created by the Composition API). In Vue 3, you can just assign them like normal objects.
+>
+> Similarly, in Vue 2 you will need to call `del` to [ensure a key deletion triggers view updates](https://vuejs.org/v2/api/#Vue-delete) in reactive objects (similar to `Vue.delete` but for `reactive objects` created by the Composition API). In Vue 3 you can just delete them by calling `delete foo.bar`.
 
 ```ts
 import { reactive, set } from '@vue/composition-api'
@@ -214,6 +218,9 @@ const a = reactive({
 
 // add new reactive key
 set(a, 'bar', 1)
+
+// remove a key and trigger reactivity
+del(a, 'bar')
 ```
 
 </details>
@@ -441,7 +448,7 @@ app2.component('Bar', Bar) // equivalent to Vue.use('Bar', Bar)
 ⚠️ <code>toRefs(props.foo.bar)</code> will incorrectly warn when acessing nested levels of props.
 ⚠️ <code>isReactive(props.foo.bar)</code> will return false.
 </summary>
-  
+
 ```ts
 defineComponent({
   setup(props) {

src/apis/index.ts

@@ -1,4 +1,5 @@
 export {
+  del,
   isReactive,
   isRef,
   isRaw,

src/reactivity/del.ts

@@ -0,0 +1,37 @@
+import { getVueConstructor } from '../runtimeContext'
+import { hasOwn, isPrimitive, isUndef, isValidArrayIndex } from '../utils'
+
+/**
+ * Delete a property and trigger change if necessary.
+ */
+export function del(target: any, key: any) {
+  const Vue = getVueConstructor()
+  const { warn } = Vue.util
+
+  if (__DEV__ && (isUndef(target) || isPrimitive(target))) {
+    warn(
+      `Cannot delete reactive property on undefined, null, or primitive value: ${target}`
+    )
+  }
+  if (Array.isArray(target) && isValidArrayIndex(key)) {
+    target.splice(key, 1)
+    return
+  }
+  const ob = target.__ob__
+  if (target._isVue || (ob && ob.vmCount)) {
+    __DEV__ &&
+      warn(
+        'Avoid deleting properties on a Vue instance or its root $data ' +
+          '- just set it to null.'
+      )
+    return
+  }
+  if (!hasOwn(target, key)) {
+    return
+  }
+  delete target[key]
+  if (!ob) {
+    return
+  }
+  ob.dep.notify()
+}

src/reactivity/index.ts

@@ -24,3 +24,4 @@ export {
   ShallowUnwrapRef,
 } from './ref'
 export { set } from './set'
+export { del } from './del'

src/reactivity/set.ts

@@ -1,26 +1,7 @@
 import { getVueConstructor } from '../runtimeContext'
-import { isArray } from '../utils'
+import { isArray, isPrimitive, isUndef, isValidArrayIndex } from '../utils'
 import { defineAccessControl } from './reactive'
 
-function isUndef(v: any): boolean {
-  return v === undefined || v === null
-}
-
-function isPrimitive(value: any): boolean {
-  return (
-    typeof value === 'string' ||
-    typeof value === 'number' ||
-    // $flow-disable-line
-    typeof value === 'symbol' ||
-    typeof value === 'boolean'
-  )
-}
-
-function isValidArrayIndex(val: any): boolean {
-  const n = parseFloat(String(val))
-  return n >= 0 && Math.floor(n) === n && isFinite(val)
-}
-
 /**
  * Set a property on an object. Adds the new property, triggers change
  * notification and intercept it's subsequent access if the property doesn't

src/utils/utils.ts

@@ -48,10 +48,25 @@ export function assert(condition: any, msg: string) {
   if (!condition) throw new Error(`[vue-composition-api] ${msg}`)
 }
 
+export function isPrimitive(value: any): boolean {
+  return (
+    typeof value === 'string' ||
+    typeof value === 'number' ||
+    // $flow-disable-line
+    typeof value === 'symbol' ||
+    typeof value === 'boolean'
+  )
+}
+
 export function isArray<T>(x: unknown): x is T[] {
   return Array.isArray(x)
 }
 
+export function isValidArrayIndex(val: any): boolean {
+  const n = parseFloat(String(val))
+  return n >= 0 && Math.floor(n) === n && isFinite(val)
+}
+
 export function isObject(val: unknown): val is Record<any, any> {
   return val !== null && typeof val === 'object'
 }
@@ -64,6 +79,10 @@ export function isFunction(x: unknown): x is Function {
   return typeof x === 'function'
 }
 
+export function isUndef(v: any): boolean {
+  return v === undefined || v === null
+}
+
 export function warn(msg: string, vm?: Vue) {
   Vue.util.warn(msg, vm)
 }

test/v3/reactivity/del.spec.ts

@@ -0,0 +1,44 @@
+import { del, reactive, ref, watch } from '../../../src'
+
+// Vue.delete workaround for triggering view updates on object property/array index deletion
+describe('reactivity/del', () => {
+  it('should not trigger reactivity on native object member deletion', () => {
+    const obj = reactive<{ a?: object }>({
+      a: {},
+    })
+    const spy = jest.fn()
+    watch(obj, spy, { deep: true, flush: 'sync' })
+    delete obj.a // Vue 2 limitation
+    expect(spy).not.toHaveBeenCalled()
+    expect(obj).toStrictEqual({})
+  })
+
+  it('should trigger reactivity when using del on reactive object', () => {
+    const obj = reactive<{ a?: object }>({
+      a: {},
+    })
+    const spy = jest.fn()
+    watch(obj, spy, { deep: true, flush: 'sync' })
+    del(obj, 'a')
+    expect(spy).toBeCalledTimes(1)
+    expect(obj).toStrictEqual({})
+  })
+
+  it('should not remove element on array index and should not trigger reactivity', () => {
+    const arr = ref([1, 2, 3])
+    const spy = jest.fn()
+    watch(arr, spy, { flush: 'sync' })
+    delete arr.value[1] // Vue 2 limitation; workaround with .splice()
+    expect(spy).not.toHaveBeenCalled()
+    expect(arr.value).toEqual([1, undefined, 3])
+  })
+
+  it('should trigger reactivity when using del on array', () => {
+    const arr = ref([1, 2, 3])
+    const spy = jest.fn()
+    watch(arr, spy, { flush: 'sync' })
+    del(arr.value, 1)
+    expect(spy).toBeCalledTimes(1)
+    expect(arr.value).toEqual([1, 3])
+  })
+})