Contracts in actions

lib/hanami/action.rb

@@ -39,7 +39,7 @@ def self.gem_loader
         loader.ignore(
           "#{root}/hanami-controller.rb",
           "#{root}/hanami/controller/version.rb",
-          "#{root}/hanami/action/{constants,errors,params,validatable}.rb"
+          "#{root}/hanami/action/{constants,errors,params,contract,validatable}.rb"
         )
         loader.inflector.inflect("csrf_protection" => "CSRFProtection")
       end
@@ -109,6 +109,7 @@ def self.inherited(subclass)
       if instance_variable_defined?(:@params_class)
         subclass.instance_variable_set(:@params_class, @params_class)
       end
+
     end
 
     # Returns the class which defines the params
@@ -134,10 +135,25 @@ def self.params_class
     # @api public
     # @since 2.0.0
     def self.params(_klass = nil)
+
       raise NoMethodError,
             "To use `params`, please add 'hanami/validations' gem to your Gemfile"
     end
 
+    # Placeholder implementation for contract class method
+    #
+    # Raises a developer friendly error to include `hanami/validations`.
+    #
+    # @raise [NoMethodError]
+    #
+    # @api public
+    # @since 2.2.0
+    def self.contract
+
+      raise NoMethodError,
+            "To use `contract`, please add 'hanami/validations' gem to your Gemfile"
+    end
+
     # @overload self.append_before(*callbacks, &block)
     #   Define a callback for an Action.
     #   The callback will be executed **before** the action is called, in the
@@ -305,8 +321,8 @@ def call(env)
       response = nil
 
       halted = catch :halt do
-        params   = self.class.params_class.new(env)
-        request  = build_request(
+        params = self.class.params_class.new(env)
+        request = build_request(
           env: env,
           params: params,
           session_enabled: session_enabled?

lib/hanami/action/contract.rb

@@ -0,0 +1,139 @@
+# frozen_string_literal: true
+
+module Hanami
+  class Action
+    # A wrapper for defining validation rules using Dry::Validation. This class essentially
+    # wraps a Dry::Validation::Contract and acts as a proxy to actually use Dry gem
+    #
+    # Defined via the `contract` block in an action class.
+    # Although more complex domain-specific validations, or validations concerned with things such as uniqueness
+    # are usually better performed at layers deeper than your HTTP actions, Contract still provides helpful features
+    # that you can use without contravening the advice form above.
+    #
+    # @since 2.2.0
+    class Contract
+      # A wrapper for the result of a contract validation
+      # @since 2.2.0
+      # @api private
+      class Result < SimpleDelegator
+        # @since 2.0.0
+        # @api private
+        def output
+          __getobj__.to_h
+        end
+
+        # @since 2.0.0
+        # @api private
+        def messages
+          __getobj__.errors.to_h
+        end
+      end
+
+      # @attr_reader env [Hash] the Rack env
+      #
+      # @since 2.2.0
+      # @api private
+      attr_reader :env
+
+      # Define a contract for the given action
+      #
+      # @param blk [Proc] the block to define the contract, including [Params] as a contract schema and connected rules
+      #
+      # @since 2.2.0
+      # @api private
+      #
+      # @example
+      # class Create < Hanami::Action
+      #   contract do
+      #     params do
+      #       required(:birth_date).value(:date)
+      #     end
+      #     rule(:birth_date) do
+      #       key.failure('you must be 18 years or older to register') if value > Date.today - 18.years
+      #     end
+      #   end
+      #
+      #   def handle(req, *)
+      #     halt 400 unless req.contract.call.errors.empty?
+      #     # ...
+      #   end
+      # end
+      def self.contract(&blk)
+        validations(&blk || -> {})
+      end
+
+      # @since 2.2.0
+      # @api private
+      class << self
+        def validations(&blk)
+          @_validator = Dry::Validation::Contract.build(&blk)
+        end
+
+        attr_reader :_validator
+      end
+
+      # Initialize the contract and freeze it.
+      #
+      # @param env [Hash] a Rack env or an hash of params.
+      #
+      # @return [Hash]
+      #
+      # @since 2.2.0
+      # @api public
+      def initialize(env)
+        @env = env
+        @input = Hanami::Action::ParamsExtraction.new(env).call
+        validation = validate
+        @params = validation.to_h
+        @errors = Hanami::Action::Params::Errors.new(validation.messages)
+        freeze
+      end
+
+      attr_reader :errors
+
+      # Returns true if no validation errors are found,
+      # false otherwise.
+      #
+      # @return [TrueClass, FalseClass]
+      #
+      # @since 2.2.0
+      #
+      def valid?
+        errors.empty?
+      end
+
+      # Serialize validated params to Hash
+      #
+      # @return [::Hash]
+      #
+      # @since 2.2.0
+      def to_h
+        validate.output
+      end
+      alias_method :to_hash, :to_h
+
+      attr_reader :result
+
+      # Returns the value for the given params key.
+      #
+      # @param key [Symbol] the key
+      #
+      # @return [Object,nil] the associated value, if found
+      #
+      # @since 2.2.0
+      # @api public
+      def [](key)
+        @params[key]
+      end
+
+      private
+
+      # @since 2.2.0
+      def validate
+        Result.new(
+          self.class._validator.call(@input)
+        )
+      end
+    end
+  end
+end

lib/hanami/action/params_extraction.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "rack/request"
+
+module Hanami
+  class Action
+    # since 2.2.0
+    # @api private
+    class ParamsExtraction
+      def initialize(env)
+        @env = env
+      end
+
+      def call
+        _extract_params
+      end
+
+      private
+
+      attr_reader :env
+
+      def _extract_params
+        result = {}
+
+        if env.key?(Action::RACK_INPUT)
+          result.merge! ::Rack::Request.new(env).params
+          result.merge! _router_params
+        else
+          result.merge! _router_params(env)
+          env[Action::REQUEST_METHOD] ||= Action::DEFAULT_REQUEST_METHOD
+        end
+
+        result
+      end
+
+      def _router_params(fallback = {})
+        env.fetch(ROUTER_PARAMS) do
+          if (session = fallback.delete(Action::RACK_SESSION))
+            fallback[Action::RACK_SESSION] = Utils::Hash.deep_symbolize(session)
+          end
+
+          fallback
+        end
+      end
+    end
+  end
+end

lib/hanami/action/validatable.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require_relative "params"
+require_relative "contract"
 
 module Hanami
   class Action
@@ -17,6 +18,12 @@ module Validatable
       # @since 0.3.0
       PARAMS_CLASS_NAME = "Params"
 
+      # Defines the contract base class
+      #
+      # @api private
+      # @since 2.2.0
+      CONTRACT_CLASS_NAME = "Contract"
+
       # @api private
       # @since 0.1.0
       def self.included(base)
@@ -102,7 +109,14 @@ def params(klass = nil, &blk)
             klass = const_set(PARAMS_CLASS_NAME, Class.new(Params))
             klass.class_eval { params(&blk) }
           end
+          @params_class = klass
+        end
 
+        # @since 2.2.0
+        # @api public
+        def contract(&blk)
+          klass = const_set(CONTRACT_CLASS_NAME, Class.new(Contract))
+          klass.class_eval { contract(&blk) }
           @params_class = klass
         end
       end

spec/isolation/without_hanami_validations_spec.rb

@@ -15,6 +15,10 @@
     expect(defined?(Hanami::Action::Params)).to be(nil)
   end
 
+  it "doesn't load Hanami::Action::Contract" do
+    expect(defined?(Hanami::Action::Contract)).to be(nil)
+  end
+
   it "doesn't have params DSL" do
     expect do
       Class.new(Hanami::Action) do
@@ -28,6 +32,24 @@
     )
   end
 
+  it "doesn't have contract DSL" do
+    expect do
+      Class.new(Hanami::Action) do
+        contract do
+          params do
+            required(:start_date).value(:date)
+          end
+          rule(:start_date) do
+            key.failure('must be in the future') if value <= Date.today
+          end
+        end
+      end
+    end.to raise_error(
+      NoMethodError,
+      /To use `contract`, please add 'hanami\/validations' gem to your Gemfile/
+    )
+  end
+
   it "has params that don't respond to .valid?" do
     action = Class.new(Hanami::Action) do
       def handle(req, res)

spec/support/fixtures.rb

@@ -1902,3 +1902,62 @@ def call(env)
     end
   end
 end
+
+class ContractAction < Hanami::Action
+  contract do
+    params do
+      required(:birth_date).filled(:date)
+      required(:book).schema do
+        required(:title).filled(:str?)
+      end
+    end
+
+    rule(:birth_date) do
+      key.failure("you must be 18 years or older") if value < Date.today << (12 * 18)
+    end
+  end
+
+  def handle(request, response)
+    if request.params.valid?
+      response.status = 201
+      response.body = JSON.generate(
+        new_name: request.params[:book][:title].upcase
+      )
+    else
+      response.body = { errors: request.params.errors.to_h }
+      response.status = 302
+    end
+  end
+end
+
+class BaseContract < Hanami::Action::Contract
+  contract do
+    params do
+      required(:start_date).value(:date)
+    end
+
+    rule(:start_date) do
+      key.failure('must be in the future') if value <= Date.today
+    end
+  end
+end
+
+AddressSchema = Dry::Schema.Params do
+  required(:country).value(:string)
+  required(:zipcode).value(:string)
+  required(:street).value(:string)
+end
+
+ContactSchema = Dry::Schema.Params do
+  required(:email).value(:string)
+  required(:mobile).value(:string)
+end
+
+class OutsideSchemasContract < Hanami::Action::Contract
+  contract do
+    params(AddressSchema, ContactSchema) do
+      required(:name).value(:string)
+      required(:age).value(:integer)
+    end
+  end
+end