Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 #3

cuixiaorui · 2021-12-12T08:42:01Z

Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701

为什么要读他

和 reactive and ref type infer is Wrong #1111 #2 有相关
通过 pr 的方式修复 bug 的流程

可以学到什么

todo

开始时间

2021-12-13

12月第三周

likui628 · 2021-12-12T11:30:10Z

版本

3.2.19

重现

点击gitpod工程
ctrl + ~打开终端
npm install安装依赖
npm run build

> [email protected] build
> tsc -p tsconfig.json

index.ts:3:17 - error TS4058: Return type of exported function has or is using name 'RefSymbol' from external module "/workspace/vue-refsymbol-issue/node_modules/@vue/reactivity/dist/reactivity" but cannot be named.

3 export function useCounter () {
                  ~~~~~~~~~~


Found 1 error.

原因

以下是出问题的代码，

import { ref, readonly } from 'vue'

export function useCounter () {
  const count = ref(0)

  function increment () {
    count.value++
  }

  return {
    count: readonly(count),
    increment
  }
}

问题就出在返回的count: readonly(count),count的类型被解析为RefSymbol，但是RefSymbol为私有的symbol。

那么由此可以推测问题出在readonly函数,ctrl+鼠标左键查看readonly定义

/**
 * Creates a readonly copy of the original object. Note the returned copy is not
 * made reactive, but `readonly` can be called on an already reactive object.
 */
export declare function readonly<T extends object>(target: T): DeepReadonly<UnwrapNestedRefs<T>>;

因此我们需要再去看DeepReadonly定义

type Primitive = string | number | boolean | bigint | symbol | undefined | null
type Builtin = Primitive | Function | Date | Error | RegExp
export type DeepReadonly<T> = T extends Builtin
  ? T
  : T extends Map<infer K, infer V>
  ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>>
  : T extends ReadonlyMap<infer K, infer V>
  ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>>
  : T extends WeakMap<infer K, infer V>
  ? WeakMap<DeepReadonly<K>, DeepReadonly<V>>
  : T extends Set<infer U>
  ? ReadonlySet<DeepReadonly<U>>
  : T extends ReadonlySet<infer U>
  ? ReadonlySet<DeepReadonly<U>>
  : T extends WeakSet<infer U>
  ? WeakSet<DeepReadonly<U>>
  : T extends Promise<infer U>
  ? Promise<DeepReadonly<U>>
  : T extends {}
  ? { readonly [K in keyof T]: DeepReadonly<T[K]> }
  : Readonly<T>

于是我们可以尝试去重现这个问题TS Playground

type Primitive = string | number | boolean | bigint | symbol | undefined | null
type Builtin = Primitive | Function | Date | Error | RegExp
export type DeepReadonly<T> = T extends Builtin
  ? T
  : T extends {}
  ? { readonly [K in keyof T]: DeepReadonly<T[K]> }
  : Readonly<T>

declare const RefSymbol: unique symbol

export interface Ref<T = any> {
  value: T
  [RefSymbol]: true
}

/*
type test = {
  readonly value: number;
  readonly [RefSymbol]: true;
}
 */
type test = DeepReadonly<Ref<number>>

因此可以判定问题就出在DeepReadonly没有特殊处理Ref类型，错误的将RefSymbol暴露出来。

解决

修复只需要增加Ref类型的判断TS Playground

type Primitive = string | number | boolean | bigint | symbol | undefined | null
type Builtin = Primitive | Function | Date | Error | RegExp
export type DeepReadonly<T> = T extends Builtin
  ? T
  : T extends Ref<infer U>
  //增加Ref类型判断
  ? Ref<DeepReadonly<U>>
  : T extends {}
  ? { readonly [K in keyof T]: DeepReadonly<T[K]> }
  : Readonly<T>

declare const RefSymbol: unique symbol

export interface Ref<T = any> {
  value: T
  [RefSymbol]: true
}

/*
type test = Ref<number>
 */
type test = DeepReadonly<Ref<number>>

emwanwei163 · 2021-12-12T14:11:45Z

由于在fix issue 1111的 PR里面引入了 [RefSymbol]

DeepReadonly把这个 [RefSymbol]也标记为 readonly了，说明对Ref类型的对象也进行了递归readonly处理。
出错是因为[RefSymbol]没有被导出。declare const RefSymbol: unique symbol (在这个declare const 前面加export可能就不报错了，但是不符合作者的目的）

fix是加入对Ref类型的判断

收获1 unique symbol的使用

看历史记录，作者在这里是有几次不同的改动的。
使用过 const isRefSymbol = Symbol()
意图是用isRefSymbol来区别Ref对象和恰好带value的普通对象。但是对任意对象检查symbol比检查普通property慢很多，所以还是加入了普通property __v_isRef: true
然后isRefSymbol就删了
接着在commit b772bba5587726e78b20ccb9b61374120bd4b0ae 引入DeepReadonly
后来呢，又把这个revert了，Symbol改为了unique symbol. 然后 __v_isRef 被封装到了RefImpl里面。

class RefImpl<T> {
  private _value: T
  private _rawValue: T

  public dep?: Dep = undefined
  public readonly __v_isRef = true

这个就是和issue1111相关联的，达到的效果是 [RefSymbol] 在 d.ts里面可见，但是IDE打点点不出来，而且这个unique symbol只用作标记类型用，对象并不会有这个值。但是对_shallow属性由于注释里面写@internal，d.ts看不到，但是对象里面存在。 (只让用户看见和自动补齐value)

编译后

export declare interface Ref<T = any> {
    value: T;
    /**
     * Type differentiator only.
     * We need this to be in public d.ts but don't want it to show up in IDE
     * autocomplete, so we use a private Symbol instead.
     */
    [RefSymbol]: true;
    /* Excluded from this release type: _shallow */
}

可以对比一下有没有[RefSymbol]的效果
有的[RefSymbol]的情况

export interface Ref<T = any> {
  value: T
  [RefSymbol]: true
}

type Fake = { value: number }

type TestRef<T> = T extends Ref<infer U> ? U : T;
type Result = TestRef<Fake>  // 此处判断正确  type Result = { value: number }

没有的情况

export interface Ref<T = any> {
  value: T
}

type Fake = { value: number }

type TestRef<T> = T extends Ref<infer U> ? U : T;
type Result = TestRef<Fake>  // 此处判断错误  type Result = number， 无法区分假的带value的类型

收获2 这个DeepReadonly 足够全面的写法

对DeepReadonly的实现再复习一下思路。

对ReadOnly的实现梳理一下记忆
比如有个utiltiy type的作用是产生和输入类型一样
type Same<T> = { [P in keyof T] : T[P] }
然后在每个属性上面加readonly, 这就是系统提供的基本ReadOnly
type ReadOnly<T> = { readonly [P in keyof T] : T[P] }
但是要对子类型递归的处理就需要DeepReadonly
直观的想法就是对 T[P] 也都加上 readonly
type DeepReadonly<T> = { readonly [P in keyof T] : DeepReadonly<T[P]> } // 但是这个没有条件判断, 递归不起来
那么加上条件判断就是
type DeepReadonly<T> = { readonly [P in keyof T] : T[P] 是基本类型吗 ? T[P] : DeepReadonly<T[P]> }

于是就有关于T[P] 是否为基本类型的判断方式, 比如 T[P] extends string | number | Function | Array<infer _> 这样的
type DeepReadonly<T> = { readonly [P in keyof T] : T[P] extends string | number | Function | Array<infer _> ? T[P] : DeepReadonly<T[P]> }
为了递归看起来简洁，就把判断基本类型放前面
type DeepReadonly<T> = T extends string | number | Function | Array<infer _> ? T : { readonly [P in keyof T] : DeepReadonly<T[P]> }
或者有人有更好的写法
type DeepReadonly<T> = keyof T extends never ? T : { readonly [P in keyof T] : DeepReadonly<T[P]> }
vue3里面的写法更严谨全面
不仅判断基本类型，还判断内建类型

type Primitive = string | number | boolean | bigint | symbol | undefined | null
type Builtin = Primitive | Function | Date | Error | RegExp

而且对Map, ReadOnlyMap, WeakMap, Set, ReadOnlySet, WeakSet都进行了判断和处理
虽然这是一个类似带很多if else的类型判断，感觉逻辑很清晰，好像有个处理的图表

- Map<infer K, infer V> ---------> ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>>        
- ReadOnlyMap< .. > -------------> ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>> 
- WeakMap<infer K, infer V> -----> WeakMap<DeepReadonly<K>, DeepReadonly<V>>                 

- Set<infer U> -------------------> ReadonlySet<DeepReadonly<U>>
- ReadonlySet<infer U> -----------> ReadonlySet<DeepReadonly<U>>
- WeakSet<infer U> ---------------> WeakSet<DeepReadonly<U>>

另外再加Promise和Ref, 然后对{}就是普通的递归了

shuzong · 2021-12-13T08:56:25Z

版本：3.2.19

产生issue实例：

import { ref, readonly } from 'vue'

export function useCounter() {
  const count = ref(0)

  function increment () {
    count.value++
  }

  return {
    count: readonly(count),
    increment
  }
}

ide和build时报错：index.ts:3:17 - error TS4058: Return type of exported function has or is using name 'RefSymbol' from external module "vue-refsymbol-issue-master/node_modules/@vue/reactivity/dist/reactivity" but cannot be named.

首先解读RefSymbol，这是什么？作者代码里没有提到RefSymbol，那我可不可以试着看函数返回对象类型定义

function useCounter(): {
    count: {
        readonly value: number;
        readonly [RefSymbol]: true;
    };
    increment: () => void;
}

有发现了，这里返回的count是个对象，拥有只读value和[RefSymbol]属性，那此时我觉得我应该看看count声明是ref到底做了什么？

export declare interface Ref<T = any> {
    value: T;
    /**
     * Type differentiator only.
     * We need this to be in public d.ts but don't want it to show up in IDE
     * autocomplete, so we use a private Symbol instead.
     */
    [RefSymbol]: true;
    /* Excluded from this release type: _shallow */
}

找到[RefSymbol]了，是ref生成时定义的接口类型，那我看看ref初始化方法吧

export function ref(value?: unknown) {
  return createRef(value, false)
}

function createRef(rawValue: unknown, shallow: boolean) {
  if (isRef(rawValue)) {
    return rawValue
  }
  return new RefImpl(rawValue, shallow)
}

看到这里，我看出ref对象拥有value和[RefSymbol]属性，那为什么readonly后就没有该属性了？是不是readonly出了问题，一起看看readonly吧

export declare function readonly<T extends object>(target: T): DeepReadonly<UnwrapNestedRefs<T>>;

DeepReadonly
export declare type DeepReadonly<T> = T extends Builtin 
   ? T : T extends Map<infer K, infer V> 
   ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>> : T extends ReadonlyMap<infer K, infer V> 
   ? ReadonlyMap<DeepReadonly<K>, DeepReadonly<V>> : T extends WeakMap<infer K, infer V> 
   ? WeakMap<DeepReadonly<K>, DeepReadonly<V>> : T extends Set<infer U> 
   ? ReadonlySet<DeepReadonly<U>> : T extends ReadonlySet<infer U> 
   ? ReadonlySet<DeepReadonly<U>> : T extends WeakSet<infer U> 
   ? WeakSet<DeepReadonly<U>> : T extends Promise<infer U> 
   ? Promise<DeepReadonly<U>> : T extends {} 
   ? {
    readonly [K in keyof T]: DeepReadonly<T[K]>;
} : Readonly<T>;

DeepReadonly缺少对ref类型的处理，试着根据其他声明类型把ref加上

? Ref<DeepReadonly<U>> : T extends Ref<infer U>

尝试npm run build试一下

嗯，可以了，IDE也不报错了

此bug尝试解除，源码其实并没有看的特别懂，还是需要一步步查和扩展思路，通过这个bug和之前的reactive and ref type infer is Wrong #1111 #2，让我对ref对象创建和生成更加了解

ps：看源码时遇到了一行不太理解，不会通过jest去查，
声明ref(0)后在，在ref对象初始化时

function createRef(rawValue: unknown, shallow: boolean) {
  if (isRef(rawValue)) {
    return rawValue
  }
  return new RefImpl(rawValue, shallow)
}

可知rawValue为0

export function isRef(r: any): r is Ref {
  return Boolean(r && r.__v_isRef === true)
}

r为0的情况下，r && r.__v_isRef === true，这句话应该不成立的

没有时间继续深入看了记录一下

jp-liu · 2021-12-14T00:09:01Z

@shuzong 如果是 Ref 那么他就是一个 RefImpl 类, 不是 0 去做比较

shuzong · 2021-12-14T02:06:11Z

@shuzong如果的英文Ref那么他就是一个RefImpl类，不是0去做比较

十分感谢，昨晚我也看了一下，参数并不是int类型的0

cuixiaorui changed the title ~~fix(types): ensure that DeepReadonly handles Ref type properly (fix #4701) #4714~~ Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 Dec 12, 2021

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Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 #3

Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 #3

cuixiaorui commented Dec 12, 2021 •

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likui628 commented Dec 12, 2021 •

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emwanwei163 commented Dec 12, 2021 •

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shuzong commented Dec 13, 2021

jp-liu commented Dec 14, 2021

shuzong commented Dec 14, 2021

Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 #3

Generating declarations for readonly/shallowReadonly ref causes TS4058 error #4701 #3

Comments

cuixiaorui commented Dec 12, 2021 • edited Loading

为什么要读他

可以学到什么

开始时间

likui628 commented Dec 12, 2021 • edited Loading

版本

重现

原因

解决

emwanwei163 commented Dec 12, 2021 • edited Loading

由于在fix issue 1111的 PR里面引入了 [RefSymbol]

fix是加入对Ref类型的判断

收获1 unique symbol的使用

收获2 这个DeepReadonly 足够全面的写法

shuzong commented Dec 13, 2021

jp-liu commented Dec 14, 2021

shuzong commented Dec 14, 2021

cuixiaorui commented Dec 12, 2021 •

edited

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likui628 commented Dec 12, 2021 •

edited

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emwanwei163 commented Dec 12, 2021 •

edited

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