Raise a helpful error when an operation doesn't set result.response

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Added
+
+- Started raising a `NoResponseError` if an operation doesn't return a `result.response` skill 
+
 ## [2.2.0]
 
 ## Added

lib/pragma/rails.rb

@@ -6,13 +6,12 @@
 require 'pragma/rails/version'
 require 'pragma/rails/controller'
 require 'pragma/rails/resource_controller'
+require 'pragma/rails/errors'
 
 require 'generators/pragma/resource_generator' if defined?(::Rails::Generators)
 
 module Pragma
   # Ruby on Rails integration for the Pragma architecture.
-  #
-  # @author Alessandro Desantis
   module Rails
   end
 end

lib/pragma/rails/controller.rb

@@ -4,8 +4,6 @@ module Pragma
   module Rails
     # This mixin should be included in a Rails controller to provide integration with Pragma
     # operations.
-    #
-    # @author Alessandro Desantis
     module Controller
       def self.included(klass)
         klass.include InstanceMethods
@@ -28,6 +26,8 @@ def run(operation_klass)
             'policy.context' => policy_context
           )
 
+          fail NoResponseError unless result['result.response']
+
           result['result.response'].headers.each_pair do |key, value|
             response.headers[key] = value
           end

lib/pragma/rails/errors.rb

@@ -0,0 +1,14 @@
+module Pragma
+  module Rails
+    class NoResponseError < StandardError
+      def initialize
+        super <<~MESSAGE
+          Your operation did not return a `result.response` skill, which might mean one of the following:
+
+            * The execution of the operation halted early (maybe one of your steps returned a falsey value?).
+            * You forgot to set a `result.response` skill in a custom operation.
+        MESSAGE
+      end
+    end
+  end
+end

lib/pragma/rails/resource_controller.rb

@@ -3,8 +3,6 @@
 module Pragma
   module Rails
     # Exposes CRUD operations on a resource through a Rails controller.
-    #
-    # @author Alessandro Desantis
     module ResourceController
       def self.included(klass)
         klass.include Controller

spec/pragma/rails/controller_spec.rb

@@ -57,4 +57,29 @@ def operation_params
   it 'responds with the resource from the operation' do
     expect(subject.render_args.first[:json]).to eq('foo' => 'bar')
   end
+
+  context 'when the operation does not set a result.response skill' do
+    let(:controller_klass) do
+      Class.new do
+        attr_reader :render_args
+
+        def run_operation
+          operation = Class.new(Pragma::Operation::Base)
+          run operation
+        end
+
+        protected
+
+        def operation_params
+          ActionController::Parameters.new(foo: 'bar')
+        end
+      end.tap do |klass|
+        klass.include described_class
+      end
+    end
+
+    it 'raises a NoResponseError' do
+      expect { subject }.to raise_error(Pragma::Rails::NoResponseError)
+    end
+  end
 end