Make sure that people can't use Procs for :format_with and the exposure.

Author: Robert Ross

lib/grape/entity.rb

@@ -71,6 +71,8 @@ def self.expose(*args, &block)
         raise ArgumentError, "You may not use block-setting on multi-attribute exposures." if block_given?
       end
 
+      raise ArgumentError, "You may not use block-setting when also using " if block_given? && options[:format_with].respond_to?(:call)
+
       options[:proc] = block if block_given?
 
       args.each do |attribute|

spec/grape/entity_spec.rb

@@ -24,6 +24,10 @@
           expect{ subject.expose :name, :email, :as => :foo }.to raise_error(ArgumentError)
           expect{ subject.expose :name, :as => :foo }.not_to raise_error
         end
+
+        it 'should make sure that :format_with as a proc can not be used with a block' do
+          expect { subject.expose :name, :format_with => Proc.new {} do |object,options| end }.to raise_error(ArgumentError)
+        end
       end
 
       context 'with a block' do