rspec-openapi

Generate OpenAPI schema from RSpec request specs.

What's this?

There are some gems which generate OpenAPI specs from RSpec request specs. However, they require a special DSL specific to these gems, and we can't reuse existing request specs as they are.

Unlike such existing gems, rspec-openapi can generate OpenAPI specs from request specs without requiring any special DSL. Furthermore, rspec-openapi keeps manual modifications when it merges automated changes to OpenAPI specs in case we can't generate everything from request specs.

Installation

Add this line to your application's Gemfile:

gem 'rspec-openapi', group: :test

Usage

Run rspec with OPENAPI=1 to generate doc/openapi.yaml for your request specs.

$ OPENAPI=1 bundle exec rspec

Example

Let's say you have a request spec like this:

RSpec.describe 'Tables', type: :request do
  describe '#index' do
    it 'returns a list of tables' do
      get '/tables', params: { page: '1', per: '10' }, headers: { authorization: 'k0kubun' }
      expect(response.status).to eq(200)
    end

    it 'does not return tables if unauthorized' do
      get '/tables'
      expect(response.status).to eq(401)
    end
  end

  # ...
end

If you run the spec with OPENAPI=1,

OPENAPI=1 rspec spec/requests/tables_spec.rb

It will generate doc/openapi.yaml file like:

openapi: 3.0.3
info:
  title: rspec-openapi
paths:
  "/tables":
    get:
      summary: index
      tags:
      - Table
      parameters:
      - name: page
        in: query
        schema:
          type: integer
        example: 1
      - name: per
        in: query
        schema:
          type: integer
        example: 10
      responses:
        '200':
          description: returns a list of tables
          content:
            application/json:
              schema:
                type: array
                items:
                  type: object
                  properties:
                    id:
                      type: integer
                    name:
                      type: string
                    # ...

and the schema file can be used as an input of Swagger UI or Redoc.

Configuration

The following configurations are optional.

require 'rspec/openapi'

# Change the path to generate schema from `doc/openapi.yaml`
RSpec::OpenAPI.path = 'doc/schema.yaml'

# Change the output type to JSON
RSpec::OpenAPI.path = 'doc/schema.json'

# Or generate multiple partial schema files, given an RSpec example
RSpec::OpenAPI.path = -> (example) {
  case example.file_path
  when %r[spec/requests/api/v1/] then 'doc/openapi/v1.yaml'
  when %r[spec/requests/api/v2/] then 'doc/openapi/v2.yaml'
  else 'doc/openapi.yaml'
  end
}

# Disable generating `example`
RSpec::OpenAPI.enable_example = false

# Change `info.version`
RSpec::OpenAPI.application_version = '1.0.0'

# Set the info header details
RSpec::OpenAPI.info = {
  description: 'My beautiful API',
  license: {
    'name': 'Apache 2.0',
    'url': 'https://www.apache.org/licenses/LICENSE-2.0.html'
  }
}

# Set request `headers` - generate parameters with headers for a request
RSpec::OpenAPI.request_headers = %w[X-Authorization-Token]

# Set response `headers` - generate parameters with headers for a response
RSpec::OpenAPI.response_headers = %w[X-Cursor]

# Set `servers` - generate servers of a schema file
RSpec::OpenAPI.servers = [{ url: 'http://localhost:3000' }]

# Generate a comment on top of a schema file
RSpec::OpenAPI.comment = <<~EOS
  This file is auto-generated by rspec-openapi https://github.com/k0kubun/rspec-openapi

  When you write a spec in spec/requests, running the spec with `OPENAPI=1 rspec` will
  update this file automatically. You can also manually edit this file.
EOS

# Generate a custom description, given an RSpec example
RSpec::OpenAPI.description_builder = -> (example) { example.description }

# Change the example type(s) that will generate schema
RSpec::OpenAPI.example_types = %i[request]

Can I use rspec-openapi with $ref to minimize duplication of schema?

Yes, rspec-openapi v0.7.0+ supports $ref mechanism and generates schemas under #/components/schemas with some manual steps.

1. First, generate plain OpenAPI file.
2. Then, manually replace the duplications with $ref.

paths:
  "/users":
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/User"
  "/users/{id}":
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/User"
# Note) #/components/schamas is not needed to be defined. 

3. Then, re-run rspec-openapi. It will generate #/components/schemas with the referenced schema (User for example) newly-generated or updated.

paths:
  "/users":
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/User"
  "/users/{id}":
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/User"
components:
  schemas:
    User:
      type: object
      properties:
        id:
          type: string
        name:
          type: string
        role:
          type: array
          items:
            type: string

rspec-openapi also supports $ref in properties of schemas. Example)

paths:
  "/locations":
    get:
      responses:
        '200':
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/Location"
components:
  schemas:
    Location:
      type: object
      properties:
        id:
          type: string
        name:
          type: string
        Coordinate:
          "$ref": "#/components/schemas/Coordinate"
    Coordinate:
      type: object
      properties:
        lat:
          type: string
        lon:
          type: string

Note that automatic schemas update feature is still new and may not work in complex scenario. If you find a room for improvement, open an issue.

How can I add information which can't be generated from RSpec?

rspec-openapi tries to keep manual modifications as much as possible when generating specs. You can directly edit doc/openapi.yaml as you like without spoiling the automatic generation capability.

Can I exclude specific specs from OpenAPI generation?

Yes, you can specify openapi: false to disable the automatic generation.

RSpec.describe '/resources', type: :request, openapi: false do
  # ...
end

# or

RSpec.describe '/resources', type: :request do
  it 'returns a resource', openapi: false do
    # ...
  end
end

Customizations

Some examples' attributes can be overwritten via RSpec metadata options. Example:

  describe 'GET /api/v1/posts', openapi: {
    summary: 'list all posts',
    description: 'list all posts ordered by pub_date',
    tags: %w[v1 posts],
  } do
    # ...
  end

NOTE: description key will override also the one provided by RSpec::OpenAPI.description_builder method.

Links

Existing RSpec plugins which have OpenAPI integration:

• zipmark/rspec_api_documentation
• rswag/rswag
• drewish/rspec-rails-swagger

Acknowledgements

This gem was heavily inspired by the following gem:

• r7kamura/autodoc

License

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