@IsOptional()

今天在找驗證錯誤的 bug，發現有點誤解 IsOptional 的用法，看 code 的註解還是不太懂，missing 到底是指什麼

• source code 的註解

import { ValidationOptions } from '../ValidationOptions';
/**
 * Checks if value is missing and if so, ignores all validators.
 */
export declare function IsOptional(validationOptions?: ValidationOptions): PropertyDecorator;

看官方的文件才發現，有種想發個 PR 的衝動XDD

• Checks if given value is empty (=== null, === undefined) and if so, ignores all the validators on the property.

測試範例

import { IsNumber, IsOptional, validateSync } from 'class-validator'

class SomeClass {
  @IsOptional() // 如果 value 是 null / undefined -> 就不驗證
  @IsNumber({ allowNaN: false })
  something: number | null

  constructor(something?: number | null) {
    this.something = something ?? null
  }
}

const a = new SomeClass() // something 為 null -> 不驗證
console.log(validateSync(a).length) // 0

const b = new SomeClass(NaN) // something 為 NaN -> 會驗證 -> 驗證沒過
console.log(validateSync(b).length) // 1