no-throw-literal.md

description
Disallow throwing literals as exceptions.

🛑 This file is source code, not the primary documentation location! 🛑

See https://typescript-eslint.io/rules/no-throw-literal for documentation.

It is considered good practice to only throw the Error object itself or an object using the Error object as base objects for user-defined exceptions. The fundamental benefit of Error objects is that they automatically keep track of where they were built and originated.

This rule restricts what can be thrown as an exception. When it was first created, it only prevented literals from being thrown (hence the name), but it has now been expanded to only allow expressions which have a possibility of being an Error object. With the allowThrowingAny and allowThrowingUnknown, it can be configured to only allow throwing values which are guaranteed to be an instance of Error.

Rule Details

This rule is aimed at maintaining consistency when throwing exception by disallowing to throw literals and other expressions which cannot possibly be an Error object.

Examples of code for this rule:

❌ Incorrect

/*eslint @typescript-eslint/no-throw-literal: "error"*/

throw 'error';

throw 0;

throw undefined;

throw null;

const err = new Error();
throw 'an ' + err;

const err = new Error();
throw `${err}`;

const err = '';
throw err;

function err() {
  return '';
}
throw err();

const foo = {
  bar: '',
};
throw foo.bar;

✅ Correct

/*eslint @typescript-eslint/no-throw-literal: "error"*/

throw new Error();

throw new Error("error");

const e = new Error("error");
throw e;

try {
    throw new Error("error");
} catch (e) {
    throw e;
}

const err = new Error();
throw err;

function err() {
  return new Error();
}
throw err();

const foo = {
  bar: new Error();
}
throw foo.bar;

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

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,
};