prefer-promise-reject-errors

Require using Error objects as Promise rejection reasons.

✅

Extending "plugin:@typescript-eslint/recommended-type-checked" in an ESLint configuration enables this rule.

💭

This rule requires type information to run.

This rule extends the base eslint/prefer-promise-reject-errors rule. It uses type information to enforce that Promises are only rejected with Error objects.

Examples

❌ Incorrect

Promise.reject('error');

const err = new Error();
Promise.reject('an ' + err);

new Promise((resolve, reject) => reject('error'));

new Promise((resolve, reject) => {
  const err = new Error();
  reject('an ' + err);
});

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✅ Correct

Promise.reject(new Error());

class CustomError extends Error {
  // ...
}
Promise.reject(new CustomError());

new Promise((resolve, reject) => reject(new Error()));

new Promise((resolve, reject) => {
  class CustomError extends Error {
    // ...
  }
  return reject(new CustomError());
});

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How to Use

Flat Config

eslint.config.mjs

export default tseslint.config({
  rules: {
    // Note: you must disable the base rule as it can report incorrect errors
    "prefer-promise-reject-errors": "off",
    "@typescript-eslint/prefer-promise-reject-errors": "error"
  }
});

Legacy Config

.eslintrc.cjs

module.exports = {
  "rules": {
    // Note: you must disable the base rule as it can report incorrect errors
    "prefer-promise-reject-errors": "off",
    "@typescript-eslint/prefer-promise-reject-errors": "error"
  }
};

Try this rule in the playground ↗

Options

See eslint/prefer-promise-reject-errors's options.

This rule adds the following options:

interface Options {
  /**
   * Whether to always allow throwing values typed as `any`.
   */
  allowThrowingAny?: boolean;

  /**
   * Whether to always allow throwing values typed as `unknown`.
   */
  allowThrowingUnknown?: boolean;
}

const defaultOptions: Options = {
  allowThrowingAny: false,
  allowThrowingUnknown: false,
};

When Not To Use It

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

See Troubleshooting > Linting with Type Information > Performance if you experience performance degradations after enabling type checked rules.

Resources

• Rule source
• Test source

^{Taken with ❤️ from ESLint core.}