From 36ab2ab9806d85653f928446316158538f0c840c Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Mon, 19 Aug 2019 12:05:07 -0400
Subject: [PATCH] wip: update writable computed API to match latest spec

---
 packages/runtime-core/src/apiState.ts | 19 ++++++++++++++-----
 packages/runtime-core/src/apiWatch.ts |  4 ++--
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/packages/runtime-core/src/apiState.ts b/packages/runtime-core/src/apiState.ts
index a40df59c..f50e14da 100644
--- a/packages/runtime-core/src/apiState.ts
+++ b/packages/runtime-core/src/apiState.ts
@@ -26,6 +26,7 @@ import {
 } from '@vue/reactivity'
 
 import { currentInstance } from './component'
+import { isFunction } from '@vue/shared'
 
 // record effects created during a component's setup() so that they can be
 // stopped when the component unmounts
@@ -35,12 +36,20 @@ export function recordEffect(effect: ReactiveEffect) {
   }
 }
 
-// a wrapped version of raw computed to tear it down at component unmount
-export function computed<T, C = null>(
-  getter: () => T,
-  setter?: (v: T) => void
+interface ComputedOptions<T> {
+  get: () => T
+  set: (v: T) => void
+}
+
+export function computed<T>(
+  getterOrOptions: (() => T) | ComputedOptions<T>
 ): ComputedRef<T> {
-  const c = _computed(getter, setter)
+  let c: ComputedRef<T>
+  if (isFunction(getterOrOptions)) {
+    c = _computed(getterOrOptions)
+  } else {
+    c = _computed(getterOrOptions.get, getterOrOptions.set)
+  }
   recordEffect(c.effect)
   return c
 }
diff --git a/packages/runtime-core/src/apiWatch.ts b/packages/runtime-core/src/apiWatch.ts
index 0f9e5186..c396452b 100644
--- a/packages/runtime-core/src/apiWatch.ts
+++ b/packages/runtime-core/src/apiWatch.ts
@@ -6,7 +6,7 @@ import {
   ReactiveEffectOptions
 } from '@vue/reactivity'
 import { queueJob, queuePostFlushCb } from './scheduler'
-import { EMPTY_OBJ, isObject, isArray } from '@vue/shared'
+import { EMPTY_OBJ, isObject, isArray, isFunction } from '@vue/shared'
 import { recordEffect } from './apiState'
 
 export interface WatchOptions {
@@ -60,7 +60,7 @@ export function watch(
     | WatchOptions,
   options?: WatchOptions
 ): StopHandle {
-  if (typeof effectOrOptions === 'function') {
+  if (isFunction(effectOrOptions)) {
     // effect callback as 2nd argument - this is a source watcher
     return doWatch(effectOrSource, effectOrOptions, options)
   } else {