Added custom exceptions to Grape. Updated validation errors to use ValidationError.

CHANGELOG.markdown

@@ -1,6 +1,7 @@
 Next Release
 ============
 
+* [#201](https://github.com/intridea/grape/pull/201): Added custom exceptions to Grape. Updated validations to use ValidationError that can be rescued. - [@adamgotterer](https://github.com/adamgotterer).
 * [#211](https://github.com/intridea/grape/pull/211): Updates to validation and coercion: Fix #211 and force order of operations for presence and coercion - [@adamgotterer](https://github.com/adamgotterer).
 * [#210](https://github.com/intridea/grape/pull/210): Fix: `Endpoint#body_params` causing undefined method 'size' - [@adamgotterer](https://github.com/adamgotterer).
 * [#201](https://github.com/intridea/grape/pull/201): Rewritten `params` DSL, including support for coercion and validations - [@schmurfy](https://github.com/schmurfy).

lib/grape.rb

@@ -11,6 +11,11 @@ module Grape
   autoload :Cookies,         'grape/cookies'
   autoload :Validations,     'grape/validations'
 
+  module Exceptions
+    autoload :Base, 'grape/exceptions/base'
+  end
+  autoload :ValidationError, 'grape/exceptions/validation_error'
+
   module Middleware
     autoload :Base,      'grape/middleware/base'
     autoload :Prefixer,  'grape/middleware/prefixer'

lib/grape/exceptions/base.rb

@@ -0,0 +1,17 @@
+module Grape
+  module Exceptions
+    class Base < StandardError
+      attr_reader :status, :message, :headers
+
+      def initialize(args = {})
+        @status = args[:status] || nil
+        @message = args[:message] || nil
+        @headers = args[:headers] || nil
+      end
+
+      def [](index)
+        self.send(index)
+      end 
+    end
+  end
+end

lib/grape/exceptions/validation_error.rb

@@ -0,0 +1,4 @@
+require 'grape/exceptions/base'
+
+class ValidationError < Grape::Exceptions::Base
+end

lib/grape/middleware/error.rb

@@ -44,11 +44,19 @@ def call!(env)
             return @app.call(@env) 
           })
         rescue Exception => e
-          raise unless options[:rescue_all] || (options[:rescued_errors] || []).include?(e.class)
-          handler = options[:rescue_handlers][e.class] || options[:rescue_handlers][:all]
+          is_rescuable = rescuable?(e.class)
+          if e.is_a?(Grape::Exceptions::Base) && !is_rescuable
+            handler = lambda { error_response(e) }
+          else
+            raise unless is_rescuable
+            handler = options[:rescue_handlers][e.class] || options[:rescue_handlers][:all]
+          end
           handler.nil? ? handle_error(e) : self.instance_exec(e, &handler)
         end
-
+      end
+
+      def rescuable?(klass)
+        options[:rescue_all] || (options[:rescued_errors] || []).include?(klass)
       end
 
       def handle_error(e)

lib/grape/validations/coerce.rb

@@ -12,7 +12,7 @@ def validate_param!(attr_name, params)
         if valid_type?(new_value)
           params[attr_name] = new_value
         else
-          throw :error, :status => 400, :message => "invalid parameter: #{attr_name}"
+          raise ValidationError, :status => 400, :message => "invalid parameter: #{attr_name}"
         end
       end
 

lib/grape/validations/presence.rb

@@ -1,13 +1,11 @@
 module Grape
   module Validations
-
     class PresenceValidator < Validator
       def validate_param!(attr_name, params)
         unless params.has_key?(attr_name)
-          throw :error, :status => 400, :message => "missing parameter: #{attr_name}"
+          raise ValidationError, :status => 400, :message => "missing parameter: #{attr_name}"
         end
       end
     end
-
   end
 end

lib/grape/validations/regexp.rb

@@ -4,7 +4,7 @@ module Validations
     class RegexpValidator < SingleOptionValidator
       def validate_param!(attr_name, params)
         if params[attr_name] && !( params[attr_name].to_s =~ @option )
-          throw :error, :status => 400, :message => "invalid parameter: #{attr_name}"
+          raise ValidationError, :status => 400, :message => "invalid parameter: #{attr_name}"
         end
       end
     end

spec/grape/api_spec.rb

@@ -669,6 +669,27 @@ def three
 
       lambda{ get '/unrescued' }.should raise_error
     end
+
+    it 'should not re-raise exceptions of type Grape::Exception::Base' do
+      class CustomError < Grape::Exceptions::Base; end
+      subject.get('/custom_exception'){ raise CustomError }
+
+      lambda{ get '/custom_exception' }.should_not raise_error
+    end
+
+    it 'should rescue custom grape exceptions' do
+      class CustomError < Grape::Exceptions::Base; end
+      subject.rescue_from CustomError do |e|
+        rack_response('New Error', e.status)
+      end
+      subject.get '/custom_error' do
+        raise CustomError, :status => 400, :message => 'Custom Error'
+      end
+
+      get '/custom_error'
+      last_response.status.should == 400
+      last_response.body.should == 'New Error'
+    end
   end
 
   describe ".error_format" do

spec/grape/middleware/exception_spec.rb

@@ -34,6 +34,16 @@ def call(env)
       end
     end
   end
+
+  # raises a custom error
+  class CustomError < Grape::Exceptions::Base; end
+  class CustomErrorApp
+    class << self
+      def call(env)
+        raise CustomError, :status => 400, :message => 'failed validation'
+      end
+    end
+  end
 
   def app
     @app
@@ -116,6 +126,17 @@ def app
       get '/'
       last_response.status.should == 401    
     end 
+
+    it 'should respond to custom Grape exceptions appropriately' do
+      @app ||= Rack::Builder.app do
+        use Grape::Middleware::Error, :rescue_all => false
+        run CustomErrorApp
+      end
+
+      get '/'
+      last_response.status.should == 400
+      last_response.body.should == 'failed validation'
+    end
 
   end 
 end