require-await.md

Disallow async functions which have no await expression (require-await)

Asynchronous functions that don’t use await might not need to be asynchronous functions and could be the unintentional result of refactoring.

Rule Details

The @typescript-eslint/require-await rule extends the require-await rule from ESLint core, and allows for cases where the additional typing information can prevent false positives that would otherwise trigger the rule.

One example is when a function marked as async returns a value that is:

1. already a promise; or
2. the result of calling another async function

async function numberOne(): Promise<number> {
  return Promise.resolve(1);
}

async function getDataFromApi(endpoint: string): Promise<Response> {
  return fetch(endpoint);
}

In the above examples, the core require-await triggers the following warnings:

async function 'numberOne' has no 'await' expression
async function 'getDataFromApi' has no 'await' expression

One way to resolve these errors is to remove the async keyword. However doing so can cause a conflict with the @typescript-eslint/promise-function-async rule (if enabled), which requires any function returning a promise to be marked as async.

Another way to resolve these errors is to add an await keyword to the return statements. However doing so can cause a conflict with the no-return-await rule (if enabled), which warns against using return await since the return value of an async function is always wrapped in Promise.resolve anyway.

With the additional typing information available in TypeScript code, this extension to the require-await rule is able to look at the actual return types of an async function (before being implicitly wrapped in Promise.resolve), and avoid the need for an await expression when the return value is already a promise.

See the ESLint documentation for more details on the require-await rule.

Rule Changes

{
    // note you must disable the base rule as it can report incorrect errors
    "require-await": "off",
    "@typescript-eslint/require-await": "error"
}

^{Taken with ❤️ from ESLint core}