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express-api-problem

Automatically turns your thrown exceptions to the JSON response while conforming to API problem specification

An express package that lets you handle the API problems with ease. It provides a straightforward implementation of IETF Problem Specification and turns your thrown exceptions to be returned in the below format with the header of content type set to application/problem+json

{
   "status": 403,
   "type": "http://example.com/problems/out-of-credit",
   "title": "You do not have enough credit.",
   "detail": "Your current balance is 30, but the item costs 50.",
   "instance": "http://example.net/account/12345/logs?id=233"
}

Where

  • title is the summary of problem
  • status is the status code
  • detail is human readable explanation specific to problem
  • type is the absolute URI that identifies the type of problem
  • instance is the absolute URI that identifies the specific occurrence of the problem

Installation

yarn add express-api-problem

Usage

Register the middleware in your server after the routes registration

import { ExpressMiddleware as ErrorHandler } from 'express-api-problem';

// Your routes

app.use(ErrorHandler());

Throw exceptions while instantiating ApiProblem having the following signature

import { ApiProblem, FormattedErrorType } from 'express-api-problem';

// status (required): HTTP status code to be returned
// title (optional): Title in response
// detail (optional): Description of the exception or 
// additional (optional): Object having any additional detail that you may want to send in response
throw new ApiProblem({
  status: 400,
  title: 'Validation Failed',
  detail: 'Invalid username or password given',
  type: '2882',
  instance: 'http://some.url/for/details',
});

// or call `next` with an instance of ApiProblem
next(new ApiProblem({
  status: 400,
  title: 'Insufficient Balance',
  detail: 'You do not have enough balance to purchase the product',
  additional: {
    available_balance: 'USD 2000',
    required_balance: 'USD 12422',
  },
}));

// Will return the below JSON with 400 status code and below response
// {
//   status: 400,
//   title: 'Insufficient Balance',
//   detail: 'You do not have enough balance to purchase the product',
//   available_balance: 'USD 2000',
//   required_balance: 'USD 12422',
// }

Add the mongoose plugin to automatically transform your model validation errors to API Problem

import { MongoosePlugin as ApiProblemPlugin } from 'express-api-problem/mongoose-plugin';

// Will transform any validation exceptions thrown by your model to
//
//  {
//     status: 422,
//     title: "Validation Failed",
//     detail: [
//        {
//          field: "title",
//          message: "Title must be unique"
//        },
//        {
//          field: "expiryDate",
//          message: "Expiry Date must be a valid date"
//        }
//     ]
// }
//
yourSchema.plugin(ApiProblemPlugin, {
  status: 422, // Defaults to 422, you can override here
  title: "Validation Failed", // Defaults to "Validation Failed", you can override here
  instance: null, // Add string value if any
  additional: {}, // Add more details if any
  type: "", // Add type information if any
});

Examples

Throwing exception using only status code

throw new ApiProblem();

// {
//    status: 500,
//    title: 'Internal Server Error',
//    stacktrace: "",   // if enabled while registering the middleware
// }

Providing description string

throw new ApiProblem({
  status: 400,
  title: 'An Error',
  detail: 'An Error Occurred',
  type: 'some error',
  instance: 'http://some/url',
});

// {
//   status: 404,
//   title: 'User not found',
//   detail: 'No user found against the given ID: 10',
//   type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Providing error format in the form of field and messages

throw new ApiProblem({
  status: 400,
  title: 'An Error',
  detail: [{"field": "some_field", "message": "Some validation message"}],
  type: 'some error',
  instance: 'http://some/url',
});

// {
//   status: 404,
//   title: 'User not found',
//   detail: [
//     {
//       "field": "some_field", 
//       "message": "Some validation message"
//     }
//   ],
//   type: 'https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html'
// }

Attaching more details

throw new ApiProblem({
  status: 500,
  title: 'Non existing additional data',
  detail: 'An Error Occurred',
  type: 'some error',
  additional: {
    'more': 'nested values',
  },
});

// {
//  status: 500,
//  title: 'Non existing additional data',
//  detail: 'An Error Occurred',
//  type: 'some error',
//  more: 'nested values',
// }

Contributing

Feel free to fork, enhance, create PR and lock issues.

License

MIT © Kamran Ahmed