#always-return

#Configuration

import { defineConfig, promisePlugin } from '@rslint/core';

export default defineConfig([
  promisePlugin.configs.recommended,
  {
    rules: {
      'promise/always-return': 'error',
    },
  },
]);

Require returning inside each then() to create readable and reusable Promise chains.

#Rule Details

This rule checks inline callbacks passed as the first argument to .then(). A block-bodied callback must explicitly return, throw, call process.exit(), or call process.abort() on every path. Expression-bodied arrow callbacks are allowed because their expression is implicitly returned.

Examples of incorrect code for this rule:

promise.then(function (value) {})

promise.then((value) => {
  doSomething(value)
})

promise.then((value) => {
  if (value) {
    return value
  }
})

Examples of correct code for this rule:

promise.then((value) => value * 2)

promise.then(function (value) {
  return value * 2
})

promise.then((value) => {
  if (!value) {
    throw new Error('missing value')
  }
  return value
})

#Options

#ignoreLastCallback

Pass { "ignoreLastCallback": true } to allow the last .then() callback in a promise chain to omit a return. This is useful when the last callback only performs side effects. Default is false.

{ "promise/always-return": ["error", { "ignoreLastCallback": true }] }

promise.then((value) => {
  console.log(value)
})

promise
  .then((value) => {
    console.log(value) // still incorrect: not the last callback
  })
  .then((value) => {
    console.log(value) // correct with ignoreLastCallback
  })

#ignoreAssignmentVariable

Pass { "ignoreAssignmentVariable": ["globalThis"] } to allow the last .then() callback to omit a return when it assigns to one of the configured root variables. Default is ["globalThis"].

{ "promise/always-return": ["error", { "ignoreAssignmentVariable": ["globalThis", "window"] }] }

promise.then((value) => {
  globalThis.result = value
})

promise.then((value) => {
  window.result = value
})

#Differences from ESLint

None known.

#Original Documentation

• eslint-plugin-promise: always-return