swagger_rails

Generate API documentation, including a slick discovery UI and playground, directly from your rspec integration specs. Use the provided DSL to describe and test API operations in your spec files. Then, you can easily generate corresponding swagger.json files and serve them up with an embedded version of swagger-ui. Best of all, it requires minimal coding and maintenance, allowing you to focus on building an awesome API!

And that's not all ...

Once you have a Web API that can describe itself in Swagger, you've opened the treasure chest of Swagger-based tools including a client generator that can be targeted to a wide range of popular platforms. See swagger-codegen for more details.

NOTE: It's early days so please be gentle when reporting issues :) As author of a similar project in the .NET space - Swashbuckle, that's become very popular, I think there's real potential here. Please feel free to contribute. I'll be more than happy to consider PR's ... so long as they include tests.

Getting Started

1. Add this line to your applications Gemfile:

   gem 'swagger_rails'
   

2. Run the install generator

   rails g swagger_rails:install
   

3. Create an integration spec to describe and test your API

   require 'swagger_helper'
   
   describe 'Blogs API' do
   
     path '/blogs' do
   
       post 'creates a new blog' do
         operation_description 'Detailed implementation notes for the create a new blog API endpoint'
         consumes 'application/json'
         parameter :blog, in: :body, schema: {
           type: :object,
           properties: {
             title: { :type => :string },
             content: { :type => :string }
           },
           required: [ 'title', 'content' ]
         }
   
         response '200', 'success' do
           let(:blog) { { title: 'foo', content: 'bar' } }
           run_test!
         end
   
         response '422', 'invalid request' do
           let(:blog) { { title: 'foo' } }
           run_test!
         end
       end
     end
   end
   

4. Generate the swagger.json file(s)

   rake swaggerize
   

5. Spin up your app and check out the awesome, auto-generated docs at /api-docs!

How does it Work?

There's two separate parts to swagger rails:

1. Tooling to easily generate swagger descriptions directly from your API tests/specs
2. Rails middleware to auto-magically serve a swagger-ui that's powered by those descriptions

The tooling is designed to fit seamlessly into your development workflow, with the swagger docs and UI being a by-product that you get for free ... well almost free :) You'll need to use the provided rspec DSL. But, it's an intuitive syntax (based on the swagger-spec) and, IMO, a very succint and expressive way to write api/integration tests.

Once you've generated the swagger files, the functionality to serve them up, along with the swagger-ui, is provided as a Rails Engine. After running the install generator, you'll see the following line added to routes.rb

mount SwaggerRails::Engine => '/api-docs'

This will wire up routes for the swagger docs and swagger-ui assets, all prefixed with "/api-docs". For example, if you navigate to "/api-docs/index.html" you'll get the swagger-ui. If you navigate to "/api-docs/v1/swagger.json", you'll get the swagger.json file under your app root at "swagger/v1/swagger.json" - assuming it was generated.

If you'd like your swagger resources to appear under a different base path, you can change the Engine mount point from "/api-docs" to something else.

Multiple Swagger Documents

By default, the generator will create all operation descriptions in a single swagger.json file. You can customize this by defining additional documents in the swagger_helper (installed under your spec folder) ...

RSpec.configure do |config|
  ...

  config.swagger_docs = {
    'v1/swagger.json' => {
      swagger: '2.0',
      info: {
        title: 'API V1',
        version: 'v1'
      }
    },

    'v2/swagger.json' => {
      swagger: '2.0',
      info: {
        title: 'API V2',
        version: 'v2'
      }
    }
  }
end

And then tagging your spec's with the target swagger_doc:

require 'swagger_helper'

describe 'Blogs API V2', swagger_doc: 'v2/swagger.json' do

    path '/blogs' do
      ...
    end
  end
end

Then, when you run the generator and spin up the swagger-ui, you'll see a select box in the top right allowing your audience to switch between the different API versions.

Tweaking the Swagger Document with Request Context

You can provide global metadata for Swagger documents in the swagger_helper file and this will be included in the resulting Swagger JSON when you run the "swaggerize" rake task. For the most part, this is sufficient. However, you may want to make some changes that require the current request context. This is possible by applying an optional swagger_filter in the swagger_rails initializer (installed into config/initializers):

SwaggerRails.configure do |c|
  ...

  c.swagger_filter = lambda { |swagger, env| swagger['host'] = env['HTTP_HOST'] }
end

This function will get called prior to serialization of any Swagger file and is passed the rack env for the current request. This provides a lot of flexibilty. For example, you could dynamically assign the "host" property (as shown above) or you could inspect session information or Authoriation header and remove operations based on user permissions.

Customizing the UI

The swagger-ui provides several options for customizing it's behavior, all of which are documented here https://github.com/swagger-api/swagger-ui#swaggerui. If you need to tweak these or customize the overall look and feel of your swagger-ui, then you'll need to provide your own version of index.html. You can do this with the following generator.

rails g swagger_rails:custom_ui

This will add a local version that you can customize at "app/views/swagger_rails/swagger_ui/index.html.erb"