Fix code in error responses

[tiagopog]

It fixes #17 and closes #6.

Summary

This PR brings:

• Better error responses now fully compliant with JSON API's error specs;
• New method JSONAPI::Utils#jsonapi_render_errors with the capability of rendering errors from exceptions, ActiveRecord objects and Hashes;
• Better test coverage;
• Examples and other improvements in README.

Examples

Code:

# app/controllers/users_controller.rb
  # POST /users
  def create
    user = User.new(user_params)
    if user.save
      jsonapi_render json: user, status: :created
    else
      jsonapi_render_errors json: user, status: :unprocessable_entity
    end
  end

  # PATCH /users/:id
  def update
    user = User.find(params[:id])
    if user.update(user_params)
      jsonapi_render json: user
    else
      jsonapi_render_errors Exceptions::MyCustomError.new(user)
    end
  end

# app/controllers/posts_controller.rb
  # POST /posts
  def create
    post = Post.new(post_params)
    if post.save
      jsonapi_render json: post, status: :created
    else
      errors = [{ id: 'validation', title: 'Something went wrong', code: '100' }]
      jsonapi_render_errors json: errors, status: :unprocessable_entity
    end
  end

Responses:

Endpoint:

GET http://localhost:3000/users?fields[foo]=bar&fields[foobar]=bar&include=bar

Response body:

{
  "errors": [
    {
      "title": "Invalid resource",
      "detail": "foo is not a valid resource.",
      "code": "101",
      "status": "400"
    },
    {
      "title": "Invalid resource",
      "detail": "foobar is not a valid resource.",
      "code": "101",
      "status": "400"
    },
    {
      "title": "Invalid field",
      "detail": "bar is not a valid relationship of users",
      "code": "112",
      "status": "400"
    }
  ]
}

Endpoint:

POST http://localhost:3000/users

Request body:

{
  "data": {
    "type": "users",
    "attributes": {
      "first_name": "",
      "last_name": ""
    }
  }
}

Response body:

{
  "errors": [
    {
      "title": "First name can't be blank",
      "id": "first_name",
      "code": "100",
      "status": "422"
    },
    {
      "title": "Last name can't be blank",
      "id": "last_name",
      "code": "100",
      "status": "422"
    }
  ]
}

[tiagopog]

? @mecampbellsoup @halilim

[mecampbellsoup]

LGTM 👍

[tiagopog]

@halilim:

[halilim]

👍

[tiagopog]

I will merge the changes and release the patch. Thanks folks.