ProblemDetails

ProblemDetails is an implementation of RFC7807 Problem Details for HTTP APIs.

The RFC defines a "problem detail" as a way to inform errors to clients as machine readable form in a HTTP response to avoid the need to define new error response formats for HTTP APIs.

This library also works with Rails and Sinatra, by the problem renderer that helps to respond with the problem detail form.

Currently only JSON serialization is supported.

• Provides the class that implements a Problem Details JSON Object.
• With Rails, automatically adds the renderer to respond with Content-Type: application/problem+json which works with render in controllers.

• Ruby 2.4.x, 2.5.x, 2.6.x 3.0.x 3.1.x
• Rails 4.x, 5.x
• Sinatra >= 1.4

Add this line to your application's Gemfile:

gem 'problem_details'

Or if you use with Rails, add below line instead.

gem 'problem_details-rails'

With Sinatra, add below line instead.

gem 'sinatra-problem_details'

And then execute:

$ bundle

require 'problem_details'

ProblemDetails::Document.new(status: 404).to_json

# Or status code symbol can be specified as well.
ProblemDetails::Document.new(status: :not_found).to_json

will produce:

{
  "title": "Not Found",
  "status": 404
}

As above, the value of type is implied to be about:blank by default if the value is ommited, also the value of title is filled automatically from the status code. These are described in Predefined Problem Types:

The "about:blank" URI, when used as a problem type, indicates that the problem has no additional semantics beyond that of the HTTP status code.

When "about:blank" is used, the title SHOULD be the same as the recommended HTTP status phrase for that code (e.g., "Not Found" for 404, and so on)

..."about:blank" URI is the default value for that ["type"] member. Consequently, any problem details object not carrying an explicit "type" member implicitly uses this URI.

But you may also have the need to add some little hint, e.g. as a custom detail of the problem:

ProblemDetails::Document.new(status: 503, detail: 'Database not reachable').to_json

will produce:

{
  "title": "Service Unavailable",
  "status": 503,
  "detail": "Database not reachable"
}

You can build a problem with any additional members which are described as extension members.

ProblemDetails::Document.new(
  status: :forbidden,
  type: 'https://example.com/probs/out-of-credit',
  balance: 30,
  accounts: ['/account/12345', '/account/67890'],
).to_json

will produce(note that balance and accounts are extention members):

{
  "type": "https://example.com/probs/out-of-credit",
  "title": "Forbidden",
  "status": 403,
  "balance": 30,
  "accounts": [
    "/account/12345",
    "/account/67890"
  ]
}

Once problem_details-rails gem is installed into a Rails system, a problem can be rendered with the problem detail form with Content-Type: application/problem+json.

For example, respond with validation error messages:

# app/controllers/api/posts_controller.rb
class Api::PostsController < ApplicationController
  def create
    @post = Post.new(params[:post])
    if @post.save
      render json: @post
    else
      render problem: { errors: @post.errors }, status: :unprocessable_entity
    end
  end
end

With render problem: { ... }, generated HTTP response will be like:

HTTP/1.1 422 Unprocessable Entity
Content-Type: application/problem+json; charset=utf-8

{
  "title": "Unprocessable Entity",
  "status": 422,
  "errors": {
    "body": [
      "can't be blank"
    ]
  }
}

Install sinatra-problems_details into a sinatra app, a problem is be rendered as well with Content-Type: application/problem+json.

require 'sinatra'
require 'sinatra-problem_details'

get '/' do
  status 400
  problem foo: 'bar'
end

require 'sinatra/base'
require 'sinatra-problem_details'

class MyApp < Sinatra::Base
  register Sinatra::ProblemDetails

  get '/' do
    status 400
    problem foo: 'bar'
  end
end

The sinatra apps defined in the previous sections will render:

HTTP/1.1 400 Bad Request
Content-Type: application/problem+json

{
  "title": "Bad Request",
  "status": 400,
  "foo": "bar"
}

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/nikushi/problem_details.

The gem is available as open source under the terms of the MIT License.