erreur

🛑 Erreur

Type safe custom errors

Usage

This library allows you to create custom errors with type safety. It's composed of two classes:

• Erreur: The custom error class.
• ErreursMap: A class to help you create a set of custom errors.

Erreur

The Erreur class extends the base Error class and adds the following properties:

• kind: A string that represents the kind of error.
• infos: An object that contains the kind, message and any additional information about the error

type MyErreurInfos = {
  kind: 'MyErreur';
  message: string;
  num: number;
};

const err = new Erreur<MyErreurInfos>({
  kind: 'MyErreur',
  message: 'Something went wrong',
  num: 42,
});

expect(err.kind).toBe('MyErreur');
expect(err.infos).toEqual({
  kind: 'MyErreur',
  message: 'Something went wrong',
  num: 42,
});

ErreursMap

The ErreursMap class allow you to define and manipulate a set of Erreurs.

To create an ErreursMap, create a new instance with an object as parameter. Each property of the object should be a function that take any number of arguments and return an object with message and any additional information about the error.

const UserErreurs = new ErreursMap({
  UnknownError: (error: Error) => ({ message: error.message, error }),
  UserNotFound: (userId: string) => ({ message: 'User not found', userId }),
  UserAlreadyExists: (username: string) => ({ message: 'User already exists', username }),
});

.create

Once the ErreursMap created you can use it to create Erreur instances with UserErreurs.create.[ErrorKind](...args):

const err = UserErreurs.create.UserAlreadyExists('paul-bocuse');

// err is an instance of Erreur

.is

You can check wether an error is one of the errors defined in the ErreursMap with UserErreurs.is(err):

UserErreurs.is(err); // true

Note: The .is check if the value is an instance of Erreur and if the kind is one of the errors defined in the ErreursMap.

.wrap

The .wrap method allow you to run code and return either teh result or one of the Erreur specified in the ErreursMap.

The .wrap method takes two parameters:

• fn: The function to run.
• mapOtherErr: A function that will be used to transform any error that is not one of the ErreursMap errors into a valid one.

const result = UserErreurs.wrap(
  () => {
    // this could throw
    createNewUser();
  },
  (err) => UserErreurs.create.UnknownError(err)
);

// result is either an Erreur or the result of the function

.wrapAsync

The .wrapAsync method is similar to .wrap but it takes an async function instead of a regular function and returns a Promise.