#await-thenable

#Configuration

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

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/await-thenable': 'error',
    },
  },
]);

#Rule Details

Disallow awaiting a value that is not a Thenable (Promise-like). Using await on a non-Promise value is almost always a programmer error and has no effect at runtime, since await on a non-Thenable value simply returns it immediately.

This rule also checks for await...of loops for non-async iterables and await using declarations for non-async disposable values.

It checks inputs to Promise.all, Promise.allSettled, Promise.any, and Promise.race, even when the call is not awaited. It reports array literal elements that are always non-Thenable, and arrays, tuples, or other iterable references whose value types can contain non-Thenables.

Examples of incorrect code for this rule:

async function foo() {
  await 42;
}

async function bar(x: number) {
  await x;
}

async function baz(arr: number[]) {
  for await (const item of arr) {
  }
}

Promise.all([Promise.resolve(1), 42]);

Examples of correct code for this rule:

async function foo() {
  await Promise.resolve(42);
}

async function bar(x: Promise<number>) {
  await x;
}

async function baz(iter: AsyncIterable<number>) {
  for await (const item of iter) {
  }
}

Promise.all([Promise.resolve(1), Promise.resolve(42)]);

#Differences from upstream

Rslint can resolve a computed aggregator name read directly from a constant object, such as const names = Object.freeze({ aggregate: 'all' }); Promise[names.aggregate]([1]);, and reports the non-Thenable element. With typescript-eslint v8.71.0 and eslint-utils v4.10.1, upstream's static evaluator recursively revisits this computed access while checking object mutations and gives up, so it does not report this example.

#Original Documentation

• typescript-eslint: await-thenable
• Source code