feat: support second target argument for lifecycle functions

Author: antfu

src/apis/lifecycle.ts

@@ -4,13 +4,14 @@ import {
   getVueConstructor,
   setCurrentInstance,
   getCurrentInstance,
+  ComponentInternalInstance,
 } from '../runtimeContext'
 import { currentVMInFn } from '../utils/helper'
 
 const genName = (name: string) => `on${name[0].toUpperCase() + name.slice(1)}`
 function createLifeCycle(lifeCyclehook: string) {
-  return (callback: Function) => {
-    const vm = currentVMInFn(genName(lifeCyclehook))
+  return (callback: Function, target?: ComponentInternalInstance | null) => {
+    const vm = currentVMInFn(genName(lifeCyclehook), target)
     return (
       vm && injectHookOption(getVueConstructor(), vm, lifeCyclehook, callback)
     )

src/utils/helper.ts

@@ -1,18 +1,25 @@
 import Vue, { VNode, ComponentOptions, VueConstructor } from 'vue'
 import { ComponentInstance } from '../component'
-import { getCurrentInstance, getVueConstructor } from '../runtimeContext'
+import {
+  ComponentInternalInstance,
+  getCurrentInstance,
+  getVueConstructor,
+} from '../runtimeContext'
 import { warn } from './utils'
 
-export function currentVMInFn(hook: string): ComponentInstance | undefined {
-  const vm = getCurrentInstance()
-  if (__DEV__ && !vm) {
+export function currentVMInFn(
+  hook: string,
+  target?: ComponentInternalInstance | null
+): ComponentInstance | undefined {
+  target = target || getCurrentInstance()
+  if (__DEV__ && !target) {
     warn(
       `${hook} is called when there is no active component instance to be ` +
         `associated with. ` +
         `Lifecycle injection APIs can only be used during execution of setup().`
     )
   }
-  return vm?.proxy
+  return target?.proxy
 }
 
 export function defineComponentInstance<V extends Vue = Vue>(