app-errors v0.0.3

app-errors

Set of reusable errors for apps / apis.

Installation

yarn add app-errors

Usage

import {
  AppError,
  AuthenticationError,
  AuhtorizationError,
  InternalError,
  NotImplementedError,
  ValidationError,
  wrapError
} from 'app-errors'

// AuthenticationError
try {
  parseJwt(token)
} catch (err) {
  throw new AuthenticationError({ message: 'Invalid token', err })
}

// AuthorizationError
if (user.role !== 'admin') {
  throw new AuthorizationError({ message: 'Only admin can access this resource' })
}

// InternalError
if (somethingGoneWrong) {
  throw new InternalError({ message: 'Something gone wrong' })
}

// NotImplementedError
app.post('/new-feature', (req, res, next) => {
  next(new NotImplementedError({ message: 'This feature is not implemented yet' }))
})

// ValidationError #1
const err = new ValidationError()
if (!user.email.match(/@gmail\.com$/)) {
  err.addDetail({ path: 'email', message: 'Must end with "@gmail.com"' })
}
if (!user.password) {
  err.addDetail({ path: 'password', message: 'Password is required' })
}
if (err.hasDetails()) {
  throw err
}

// ValidationError #2
const errors = [
  { path: 'email', message: 'Must end with "@gmail.com"' },
  { path: 'password', message: 'Password is required' }
]
if (errors.length) {
  throw new ValidationError({ details: errors })
}

// wrapError
try {
  someCode()
} catch (err) {
  err = wrapError(err)
  console.log(err instanceof AppError) // true
}

Options

All errors extend AppError.
AppError (as well as other error classes) accepts following options in constructor:

Default option values for each error class:

Methods

AppError#getOriginalError()

Return original error.

AppError#getType()

Return error type.

AppError#getSeverity()

Return error severity.

AppError#getStatusCode()

Return error HTTP status code.

AppError#getData()

Return error custom data.

AppError#getDetails()

Return error details.

AppError#addDetail({ path: String, message: String })

Add error detail.

AppError#addDetails(Array<{ path: String, message: String }>)

Add many error details at once.

AppError#hasDetails()

Return true if error has at least one detail.

AppError#toJSON()

Get JSON representation of error. Example:

console.log(new AuthenticationError('hello').toJSON())
/*
{
  type: 'authentication',
  severity: 'warning',
  message: 'hello',
  details: [{ path: 'email', message: 'Invalid email' }] // defaults to null if no details were added
}
*/

Note that err.data is not returned in JSON representation of error.

wrapError(err: Error) => err: AppError

wrapError converts error to AppError.
If err passed as argument is already instance of AppError then it returns passed err.
If err passed as argument is not instance of AppError it is wrapped in InternalError.

Example:

const originalErr = new Error('test')
const err = wrapError(originalErr)
console.log(err instanceof AppError) // true
console.log(err instanceof InternalError) // true
console.log(err.message) // 'Internal error'
console.log(err.getOriginalError() instanceof originalErr) // true

This method is useful when globally handling application errors:

app.use(async (ctx, next) => {
  try {
    await next()
  } catch (err) {
    err = wrapError(err)
    logError(err)
    ctx.status = err.getStatusCode()
    ctx.body = err.toJSON() // remember that ValidationError#toJSON may return array!
  }
})

function logError (err) {
  if (err.getSeverity() === 'error') {
    console.error(err.getOriginalError().stack)
  }
}