Skip to content
Biome
Docs Blog Playground

noAsyncPromiseExecutor (since v1.0.0)

Diagnostic Category: lint/suspicious/noAsyncPromiseExecutor

Sources:

Disallows using an async function as a Promise executor.

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

  1. 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.
  2. 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.

Examples

Section titled Examples

Invalid

Section titled Invalid
new Promise(async function foo(resolve, reject) {})
suspicious/noAsyncPromiseExecutor.js:1:13 lint/suspicious/noAsyncPromiseExecutor ━━━━━━━━━━━━━━━━━━━

  ✖ Promise executor functions should not be `async`.
  
  > 1 │ new Promise(async function foo(resolve, reject) {})
      │             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  

  new Promise(async (resolve, reject) => {})
suspicious/noAsyncPromiseExecutor.js:1:15 lint/suspicious/noAsyncPromiseExecutor ━━━━━━━━━━━━━━━━━━━

  ✖ Promise executor functions should not be `async`.
  
  > 1 │   new Promise(async (resolve, reject) => {})
      │               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    2 │ 
  

  new Promise(((((async () => {})))))
suspicious/noAsyncPromiseExecutor.js:1:19 lint/suspicious/noAsyncPromiseExecutor ━━━━━━━━━━━━━━━━━━━

  ✖ Promise executor functions should not be `async`.
  
  > 1 │   new Promise(((((async () => {})))))
      │                   ^^^^^^^^^^^^^^
    2 │

Valid

Section titled Valid
  new Promise((resolve, reject) => {})
  new Promise((resolve, reject) => {}, async function unrelated() {})
  new Foo(async (resolve, reject) => {})
  new Foo((( (resolve, reject) => {} )))
Section titled Related links