Function injectHook

packages/runtime-core/src/apiLifecycle.ts:20–64

(
  type: LifecycleHooks,
  hook: Function & { __weh?: Function },
  target: ComponentInternalInstance | null = currentInstance,
  prepend: boolean = false,
)

export { onActivated, onDeactivated } from './components/KeepAlive'

export function injectHook(
  type: LifecycleHooks,
  hook: Function & { __weh?: Function },
  target: ComponentInternalInstance | null = currentInstance,
  prepend: boolean = false,
): Function | undefined {
  if (target) {
    const hooks = target[type] || (target[type] = [])
    // cache the error handling wrapper for injected hooks so the same hook
    // can be properly deduped by the scheduler. "__weh" stands for "with error
    // handling".
    const wrappedHook =
      hook.__weh ||
      (hook.__weh = (...args: unknown[]) => {
        // disable tracking inside all lifecycle hooks
        // since they can potentially be called inside effects.
        pauseTracking()
        // Set currentInstance during hook invocation.
        // This assumes the hook does not synchronously trigger other hooks, which
        // can only be false when the user does something really funky.
        const reset = setCurrentInstance(target)
        const res = callWithAsyncErrorHandling(hook, target, type, args)
        reset()
        resetTracking()
        return res
      })
    if (prepend) {
      hooks.unshift(wrappedHook)
    } else {
      hooks.push(wrappedHook)
    }
    return wrappedHook
  } else if (__DEV__) {
    const apiName = toHandlerKey(ErrorTypeStrings[type].replace(/ hook$/, ''))
    warn(
      `${apiName} is called when there is no active component instance to be ` +
        `associated with. ` +
        `Lifecycle injection APIs can only be used during execution of setup().` +
        (__FEATURE_SUSPENSE__
          ? ` If you are using async setup(), make sure to register lifecycle ` +
            `hooks before the first await statement.`
          : ``),
    )
  }
}

const createHook =
  <T extends Function = () => any>(lifecycle: LifecycleHooks) =>