disallow using an async function as a Promise executor (no-async-promise-executor)

禁止使用异步函数作为 Promise executor (no-async-promise-executor)

The "extends": "eslint:recommended" property in a configuration file enables this rule.

配置文件中的 "extends": "eslint:recommended" 属性启用了此规则。

The new Promise constructor accepts an executor function as an argument, which has resolve and reject parameters that can be used to control the state of the created Promise. For example:

new Promise 构造函数接收一个 executor 函数作为参数，该函数具有 resolve 和 reject 两个参数，可用于控制创建的 Promise 的状态。例如:

const result = new Promise(function executor(resolve, reject) {
  readFile('foo.txt', function(err, result) {
    if (err) {
      reject(err);
    } else {
      resolve(result);
    }
  });
});

The executor function can also be an async function. However, this is usually a mistake, for a few reasons:

executor 函数也可以是 async function。然而，这通常是一个错误，原因如下:

• If an async executor function throws an error, the error will be lost and won’t cause the newly-constructed Promise to reject. This could make it difficult to debug and handle some errors.
• 如果异步 executor 函数抛出一个错误，这个错误将会丢失，并且不会导致新构造的 Promise 被拒绝。这可能使会调试和处理一些错误变得困难。
• If a Promise executor function is using await, this is usually a sign that it is not actually necessary to use the new Promise constructor, or the scope of the new Promise constructor can be reduced.
• 如果一个 Promise executor 函数使用了 await，这通常表示实际上没有必要使用 new Promise 构造函数，或者可以减少 new Promise 构造函数的范围。

Rule Details

This rule aims to disallow async Promise executor functions.

此规则旨在禁止使用异步的 Promise executor 函数。

Examples of incorrect code for this rule:

错误 代码示例：

const foo = new Promise(async (resolve, reject) => {
  readFile('foo.txt', function(err, result) {
    if (err) {
      reject(err);
    } else {
      resolve(result);
    }
  });
});

const result = new Promise(async (resolve, reject) => {
  resolve(await foo);
});

Examples of correct code for this rule:

正确 代码示例：

const foo = new Promise((resolve, reject) => {
  readFile('foo.txt', function(err, result) {
    if (err) {
      reject(err);
    } else {
      resolve(result);
    }
  });
});

const result = Promise.resolve(foo);

When Not To Use It

If your codebase doesn’t support async function syntax, there’s no need to enable this rule.

如果你的代码库不支持异步函数语法，则不需要启用此规则。

Version

This rule was introduced in ESLint 5.3.0.

该规则在 ESLint 5.3.0 中被引入。

Resources

• Rule source
• Documentation source