Allow global settings on Grape::Entity.

This fixes a regression introduced after merging a ruby-grape#134.
It's something undocumented before but it worked before and I don't see
anything harmful in the presence of this feature.

lib/grape_entity/entity.rb

@@ -112,12 +112,18 @@ class << self
       attr_accessor :nested_exposures
     end
 
+    @exposures = {}
+    @root_exposures = {}
+    @nested_exposures = {}
+    @nested_attribute_names = {}
+    @formatters = {}
+
     def self.inherited(subclass)
-      subclass.exposures = exposures.try(:dup) || {}
-      subclass.root_exposures = root_exposures.try(:dup) || {}
-      subclass.nested_exposures = nested_exposures.try(:dup) || {}
-      subclass.nested_attribute_names = nested_attribute_names.try(:dup) || {}
-      subclass.formatters = formatters.try(:dup) || {}
+      subclass.exposures = exposures.try(:dup)
+      subclass.root_exposures = root_exposures.try(:dup)
+      subclass.nested_exposures = nested_exposures.try(:dup)
+      subclass.nested_attribute_names = nested_attribute_names.try(:dup)
+      subclass.formatters = formatters.try(:dup)
     end
 
     # This method is the primary means by which you will declare what attributes
@@ -183,7 +189,10 @@ def self.expose(*args, &block)
     end
 
     def self.unexpose(attribute)
+      root_exposures.delete(attribute)
       exposures.delete(attribute)
+      nested_exposures.delete(attribute)
+      nested_attribute_names.delete(attribute)
     end
 
     # Set options that will be applied to any exposures declared inside the block.

spec/grape_entity/entity_spec.rb

@@ -278,6 +278,26 @@ class Parent < Person
           subject.expose(:size, format_with: :size_formatter)
           expect(subject.represent(object).send(:value_for, :size)).to eq object.class.to_s
         end
+
+        it 'works global on Grape::Entity' do
+          Grape::Entity.format_with :size_formatter do |_date|
+            self.object.class.to_s
+          end
+          object = {}
+
+          subject.expose(:size, format_with: :size_formatter)
+          expect(subject.represent(object).send(:value_for, :size)).to eq object.class.to_s
+        end
+      end
+
+      it 'works global on Grape::Entity' do
+        Grape::Entity.expose :x
+        object = { x: 11, y: 22 }
+        expect(Grape::Entity.represent(object).send(:value_for, :x)).to eq 11
+        subject.expose :y
+        expect(subject.represent(object).send(:value_for, :x)).to eq 11
+        expect(subject.represent(object).send(:value_for, :y)).to eq 22
+        Grape::Entity.unexpose :x
       end
     end
 
@@ -310,6 +330,13 @@ class Parent < Person
           end
         end
       end
+
+      it 'works global on Grape::Entity' do
+        Grape::Entity.expose :x
+        expect(Grape::Entity.exposures).to eq(x: {})
+        Grape::Entity.unexpose :x
+        expect(Grape::Entity.exposures).to eq({})
+      end
     end
 
     describe '.with_options' do