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promise-function-async

Require any function or method that returns a Promise to be marked async.

🛠

Some problems reported by this rule are automatically fixable by the --fix ESLint command line option.

💭

This rule requires type information to run.

Ensures that each function is only capable of:

  • returning a rejected promise, or
  • throwing an Error object.

In contrast, non-async Promise - returning functions are technically capable of either. Code that handles the results of those functions will often need to handle both cases, which can get complex. This rule's practice removes a requirement for creating code to handle both cases.

.eslintrc.cjs
module.exports = {
  "rules": {
    "@typescript-eslint/promise-function-async": "warn"
  }
};

Examples​

Examples of code for this rule

const arrowFunctionReturnsPromise = () => Promise.resolve('value');

function functionReturnsPromise() {
  return Promise.resolve('value');
}

Options​

This rule accepts an options object with the following properties:

interface Options {
  /**
   * Whether to consider `any` and `unknown` to be Promises.
   */
  allowAny?: boolean;
  /**
   * Any extra names of classes or interfaces to be considered Promises.
   */
  allowedPromiseNames?: string[];
  checkArrowFunctions?: boolean;
  checkFunctionDeclarations?: boolean;
  checkFunctionExpressions?: boolean;
  checkMethodDeclarations?: boolean;
}

const defaultOptions: Options = [
  {
    allowAny: true,
    allowedPromiseNames: [],
    checkArrowFunctions: true,
    checkFunctionDeclarations: true,
    checkFunctionExpressions: true,
    checkMethodDeclarations: true,
  },
];

Resources​