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BloodContracts

Simple and agile Ruby data validation tool inspired by refinement types and functional approach

  • Powerful. Algebraic Data Type guarantees that gem is enough to implement any kind of complex data validation, while Functional Approach gives you full control over validation outcomes
  • Simple. You could write your first Refinment Type as simple as single Ruby method in single class
  • Brings transparency. Comes with instrumentation tools, so now you will exactly know how often each type matches in your production
  • Rubyish. DSL is inspired by Ruby Struct. If you love Ruby way you'd like the BloodContracts types
  • Born in production. Created on basis of eBaymag project, used as a tool to control and monitor data inside API communication
Sponsored by Evil Martians
# Example of using for Rubygems API

require 'blood_contracts'
require 'net/http'
require 'json'

module RubygemsAPI
  def self.gem(name)
    Request.and_then(Response).match(name) do |request|
      uri = request.unpack
      http = Net::HTTP.new(uri.host, uri.port)
      http.use_ssl = true
      http.get(uri.request_uri).body
    end
  end

  class Json < BC::Refined
    def match
      # now it's easy to understand why we caught JSON::ParserError
      context[:response] = value.to_s
      context[:parsed] ||= ::JSON.parse(context[:response])
      self
    rescue JSON::ParserError => ex
      context[:exception] = ex # now we could easily playaround with exception and reraise it
      failure(:invalid_json)
    end

    # so the next validation in the pipe will receive parsed response, not unparsed string
    def mapped
      context[:parsed]
    end
  end

  class GemInfo < BC::Refined
    # I chose some data that is interesing for me
    INFO_KEYS = %w(name downloads info authors version homepage_uri source_code_uri)

    def match
      # We have to make sure that result is a hash with appropriate keys
      is_a_project = value.is_a?(Hash) && (INFO_KEYS - value.keys).empty?
      return failure(:reponse_is_not_gem_info) unless is_a_project

      context[:gem_info] = value.slice(*INFO_KEYS)
      self
    end

    def mapped
      context[:gem_info]
    end
  end

  class PlainTextError < BC::Refined
    def match
      context[:response] = value.to_s
      # to avoid multiple parsing of response, we'll try to save it
      context[:parsed] = JSON.parse(context[:response])
      failure(:non_plain_text_response)
    rescue JSON::ParserError
      self
    end

    def mapped
      context[:response]
    end
  end

  class Request < BC::Refined
    ROOT = "https://rubygems.org/api/v1/gems/".freeze

    def match
      context[:name] = String(value)
      context[:uri] = URI.parse("#{File.join(ROOT, context[:name])}.json")
      self
    rescue StandardError => ex
      context[:exception] = ex # now we could easily playaround with exception and reraise it
      failure(:invalid_gem_name_for_request)
    end

    def mapped
      context[:uri]
    end
  end

  # ... compose them...
  Response = PlainTextError.or_a(Json.and_then(GemInfo))
end

# ... and match!
case gem = RubygemsAPI.gem("rack")
when GemInfo
  gem.unpack # show data to user
when PlaintTextError
  {message: gem.unpack, status: 400} # wrap it into json response
else 
  # ...basically it's a case of ContractFailure, we have to improve contract then
  Honeybadger.notify("Unexpected Rubygems API behavior", context: gem.context) # or gem.messages to see only error messages
  {message: "Service is not available at the moment!", status: 500}
end

# And then in
# config/initializers/contracts.rb

module Contracts
  class YabedaInstrument
    def call(session)
      valid_marker = session.valid? ? "V" : "I"
      result = "[#{valid_marker}] #{session.result_type_name}"
      Yabeda.api_contract_matches.increment(result: result)
    end
  end
end

BloodContracts::Instrumentation.configure do |cfg|
  # Attach to every BC::Refined ancestor with RubygemsAPI::Response in the name
  cfg.instrument "RubygemsAPI::Response", Contracts::YabedaInstrument.new
end

Installation

Add this line to your application's Gemfile:

gem 'blood_contracts'

And then execute:

$ bundle

Or install it yourself as:

$ gem install blood_contracts

Usage

This gem is just facade for the whole data validation and monitoring toolset.

For deeper understanding see BloodContracts::Core, BloodContracts::Ext and BloodContracts::Instrumentation

Development

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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/sclinede/blood_contracts. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

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

Code of Conduct

Everyone interacting in the BloodContracts project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

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Tool for runtime data validation and monitoring (based on Contracts approach)

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