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https://github.com/ahx/openapi_first

openapi_first is a Ruby gem for request / response validation and contract-testing against an OpenAPI API description. It makes APIFirst easy and reliable.
https://github.com/ahx/openapi_first

api-server apifirst design-first jsonapi openapi openapi3 rack rest-api ruby web-framework

Last synced: 18 days ago
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openapi_first is a Ruby gem for request / response validation and contract-testing against an OpenAPI API description. It makes APIFirst easy and reliable.

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README 

        
# openapi_first



openapi_first is a Ruby gem for request / response validation and contract-testing against an [OpenAPI](https://www.openapis.org/) 3.0 or 3.1 API description. It makes an APIFirst workflow easy and reliable.



You can use openapi_first on production for [request validation](#request-validation) and in your tests to avoid API drift with it's request/response validation and coverage features.



## Contents



- [Rack Middlewares](#rack-middlewares)

  - [Request validation](#request-validation)

  - [Response validation](#response-validation)

- [Contract testing](#contract-testing)

  - [Coverage](#coverage)

  - [Test assertions](#test-assertions)

- [Manual use](#manual-use)

- [Framework integration](#framework-integration)

- [Configuration](#configuration)

- [Hooks](#hooks)

- [Alternatives](#alternatives)

- [Development](#development)

  - [Benchmarks](#benchmarks)

  - [Contributing](#contributing)



## Rack Middlewares



### Request validation



The request validation middleware returns a 4xx if the request is invalid or not defined in the API description. It adds a request object to the current Rack environment at `env[OpenapiFirst::REQUEST]` with the request parameters parsed exactly as described in your API description plus access to meta information from your API description. See _[Manual use](#manual-use)_ for more details about that object.



```ruby

use OpenapiFirst::Middlewares::RequestValidation, 'openapi.yaml'



# Pass `raise_error: true` to raise an error if request is invalid:

use OpenapiFirst::Middlewares::RequestValidation, 'openapi.yaml', raise_error: true

```



#### Error responses



openapi_first produces a useful machine readable error response that can be customized.

The default response looks like this. See also [RFC 9457](https://www.rfc-editor.org/rfc/rfc9457).



```json

http-status: 400

content-type: "application/problem+json"



{

  "title": "Bad Request Body",

  "status": 400,

  "errors": [

    {

      "message": "value at `/data/name` is not a string",

      "pointer": "/data/name",

      "code": "string"

    },

    {

      "message": "number at `/data/numberOfLegs` is less than: 2",

      "pointer": "/data/numberOfLegs",

      "code": "minimum"

    },

    {

      "message": "object at `/data` is missing required properties: mandatory",

      "pointer": "/data",

      "code": "required"

    }

  ]

}

```



openapi_first offers a [JSON:API](https://jsonapi.org/) error response by passing `error_response: :jsonapi`:



```ruby

use OpenapiFirst::Middlewares::RequestValidation, 'openapi.yaml, error_response: :jsonapi'

```



See details of JSON:API error response



```json

// http-status: 400

// content-type: "application/vnd.api+json"



{

  "errors": [

    {

      "status": "400",

      "source": {

        "pointer": "/data/name"

      },

      "title": "value at `/data/name` is not a string",

      "code": "string"

    },

    {

      "status": "400",

      "source": {

        "pointer": "/data/numberOfLegs"

      },

      "title": "number at `/data/numberOfLegs` is less than: 2",

      "code": "minimum"

    },

    {

      "status": "400",

      "source": {

        "pointer": "/data"

      },

      "title": "object at `/data` is missing required properties: mandatory",

      "code": "required"

    }

  ]

}

```



#### Custom error responses



You can build your own custom error response with `error_response: MyCustomClass` that implements `OpenapiFirst::ErrorResponse`.

You can define custom error responses globally by including / implementing `OpenapiFirst::ErrorResponse` and register it via `OpenapiFirst.register_error_response(my_name, MyCustomErrorResponse)` and set `error_response: my_name`.



### Response validation



This middleware raises an error by default if the response is not valid.

This can be useful in a test or staging environment, especially if you are adopting OpenAPI for an existing implementation.



```ruby

use OpenapiFirst::Middlewares::ResponseValidation, 'openapi.yaml' if ENV['RACK_ENV'] == 'test'



# Pass `raise_error: false` to not raise an error:

use OpenapiFirst::Middlewares::ResponseValidation, 'openapi.yaml', raise_error: false

```



If you are adopting OpenAPI you can use these options together with [hooks](#hooks) to get notified about requests/responses that do match your API description.



## Contract Testing



Here are two aspects of contract testing: Validation and Coverage



### Validation



By validating requests and responses, you can avoid that your API implementation processes requests or returns responses that don't match your API description. You can use [test assertions](#test-assertions) or [rack middlewares](#rack-middlewares) or manual validation to validate requests and responses with openapi_first.



### Coverage



To make sure your _whole_ API description is implemented, openapi_first ships with a coverage feature.



> [!NOTE]

> This is a brand new feature. ✨ Your feedback is very welcome.



This feature tracks all requests/responses that are validated via openapi_first and tells you about which request/responses are missing.

Here is how to set it up with [rack-test](https://github.com/rack/rack-test):



1. Register all OpenAPI documents to track coverage for. This should go at the top of your test helper file before loading your application code.

  ```ruby

  require 'openapi_first'

  OpenapiFirst::Test.setup do |test|

    test.register('openapi/openapi.yaml')

    test.minimum_coverage = 100 # (Optional) Setting this will lead to an `exit 2` if coverage is below minimum

    test.skip_response_coverage { it.status == '500' } # (Optional) Skip certain responses

  end

  ```

2. Add an `app` method to your tests, which wraps your application with silent request / response validation. This validates all requests/responses in your test run. (✷1)



  ```ruby

  def app

    OpenapiFirst::Test.app(MyApp)

  end

  ```

3. Run your tests.  The Coverage feature will tell you about missing request/responses.



  Or you can generate a Module and include it in your rspec spec_helper.rb:



  ```ruby

  config.include OpenapiFirst::Test::Methods[MyApp], type: :request

  ```



(✷1): It does not matter what method of openapi_first you use to validate requests/responses. Instead of using `OpenapiFirstTest.app` to wrap your application, you could also use the middlewares or [test assertion method](#test-assertions), but you would have to do that for all requests/responses defined in your API description to make coverage work.



### Test assertions



openapi_first ships with a simple but powerful Test method to run request and response validation in your tests without using the middlewares. This is designed to be used with rack-test or Ruby on Rails integration tests or request specs.



Here is how to set it up for Rails integration tests:



Inside your test:

```ruby

# test/integration/trips_api_test.rb

require 'test_helper'



class TripsApiTest < ActionDispatch::IntegrationTest

  include OpenapiFirst::Test::Methods



  test 'GET /trips' do

    get '/trips',

        params: { origin: 'efdbb9d1-02c2-4bc3-afb7-6788d8782b1e', destination: 'b2e783e1-c824-4d63-b37a-d8d698862f1d',

                  date: '2024-07-02T09:00:00Z' }



    assert_api_conform(status: 200)

    # assert_api_conform(status: 200, api: :v1) # Or this if you have multiple API descriptions

  end

end

```



## Manual use



Load the API description:



```ruby

require 'openapi_first'



definition = OpenapiFirst.load('openapi.yaml')

```



### Validate request



```ruby

validated_request = definition.validate_request(rack_request)



# Inspect the request and access parsed parameters

validated_request.valid?

validated_request.invalid?

validated_request.error # => Failure object or nil

validated_request.parsed_body # => The parsed request body (Hash)

validated_request.parsed_query # A Hash of query parameters that are defined in the API description, parsed exactly as described.

validated_request.parsed_path_parameters

validated_request.parsed_headers

validated_request.parsed_cookies

validated_request.parsed_params # Merged parsed path, query parameters and request body

# Access the Openapi 3 Operation Object Hash

validated_request.operation['x-foo']

validated_request.operation['operationId'] => "getStuff"

# or the whole request definition

validated_request.request_definition.path # => "/pets/{petId}"

validated_request.request_definition.operation_id # => "showPetById"



# Or you can raise an exception if validation fails:

definition.validate_request(rack_request, raise_error: true) # Raises OpenapiFirst::RequestInvalidError or OpenapiFirst::NotFoundError if request is invalid

```



### Validate response



```ruby

validated_response = definition.validate_response(rack_request, rack_response)



# Inspect the response and access parsed parameters and

validated_response.valid?

validated_response.invalid?

validated_response.error # => Failure object or nil

validated_response.status # => 200

validated_response.parsed_body

validated_response.parsed_headers



# Or you can raise an exception if validation fails:

definition.validate_response(rack_request,rack_response, raise_error: true) # Raises OpenapiFirst::ResponseInvalidError or OpenapiFirst::ResponseNotFoundError

```



## Configuration



You can configure default options globally:



```ruby

OpenapiFirst.configure do |config|

  # Specify which plugin is used to render error responses returned by the request validation middleware (defaults to :default)

  config.request_validation_error_response = :jsonapi

  # Configure if the request validation middleware should raise an exception (defaults to false)

  config.request_validation_raise_error = true

end

```



or configure per instance:



```ruby

OpenapiFirst.load('openapi.yaml') do |config|

  config.request_validation_error_response = :jsonapi

end

```



## Hooks



You can integrate your code at certain points during request/response validation via hooks.



Available hooks:



- `after_request_validation`

- `after_response_validation`

- `after_request_parameter_property_validation`

- `after_request_body_property_validation`



Setup per per instance:



```ruby

OpenapiFirst.load('openapi.yaml') do |config|

  config.after_request_validation do |validated_request|

    validated_request.valid? # => true / false

  end

  config.after_response_validation do |validated_response, request|

    if validated_response.invalid?

      warn "#{request.request_method} #{request.path}: #{validated_response.error.message}"

    end

  end

end

```



Setup globally:



```ruby

OpenapiFirst.configure do |config|

  config.after_request_parameter_property_validation do |data, property, property_schema|

    data[property] = Date.iso8601(data[property]) if property_schema['format'] == 'date'

  end

end

```



## Framework integration



Using rack middlewares is supported in probably all Ruby web frameworks.

If you are using Ruby on Rails for example, you can add the request validation middleware globally in `config/application.rb` or inside specific controllers.



The contract testing feature is designed to be used via rack-test, which should be compatible all Ruby web frameworks as well.



That aside, closer integration with specific frameworks like Sinatra, Hanami, Roda or Rails would be great. If you have ideas, pain points or PRs, please don't hesitate to [share](https://github.com/ahx/openapi_first/discussions).



## Alternatives



This gem was inspired by [committee](https://github.com/interagent/committee) (Ruby) and [Connexion](https://github.com/spec-first/connexion) (Python).

Here is a [feature comparison between openapi_first and committee](https://gist.github.com/ahx/1538c31f0652f459861713b5259e366a).



## Development



Run `bin/setup` to install dependencies.



See `bundle exec rake` to run the linter and the tests.



Run `bundle exec rspec` to run the tests only.



### Benchmarks



[Results](https://gist.github.com/ahx/e6ffced58bd2e8d5baffb2f4d2c1f823)



Run benchmarks:



```sh

cd benchmarks

bundle

bundle exec ruby benchmarks.rb

```



### Contributing



If you have a question or an idea or found a bug, don't hesitate to create an issue [on Github](https://github.com/ahx/openapi_first) or [Codeberg](https://codeberg.org/ahx/openapi_first) or say hi on [Mastodon (ruby.social)](https://ruby.social/@ahx).



Pull requests are very welcome as well, of course. Feel free to create a "draft" pull request early on, even if your change is still work in progress. 🤗