Fixes issue with class reopening and inheriting.

Exposures and formatters should appear in inherited classes even if
added after inheriting.

Author: marshall-lee

lib/grape_entity/entity.rb

@@ -103,11 +103,16 @@ class << self
       # Returns all formatters that are registered for this and it's ancestors
       # @return [Hash] of formatters
       attr_accessor :formatters
+      attr_accessor :inherited_entities
     end
 
+    @inherited_entities = []
+
     def self.inherited(subclass)
       subclass.root_exposure = root_exposure.try(:dup) || build_root_exposure
       subclass.formatters = formatters.try(:dup) || {}
+      self.inherited_entities << subclass
+      subclass.inherited_entities = []
     end
 
     # This method is the primary means by which you will declare what attributes
@@ -173,6 +178,10 @@ def self.expose(*args, &block)
           @nesting_stack.pop
         end
       end
+
+      inherited_entities.each do |entity|
+        entity.expose(*args, &block)
+      end
     end
 
     def self.build_root_exposure
@@ -264,6 +273,10 @@ def self.documentation
     def self.format_with(name, &block)
       fail ArgumentError, 'You must pass a block for formatters' unless block_given?
       formatters[name.to_sym] = block
+
+      inherited_entities.each do |entity|
+        entity.format_with(name, &block)
+      end
     end
 
     # This allows you to set a root element name for your representation.

spec/grape_entity/entity_spec.rb

@@ -272,6 +272,18 @@ class Parent < Person
           expect(subject.represent({ name: 'bar' }, serializable: true)).to eq(email: nil, name: 'bar')
           expect(child_class.represent({ name: 'bar' }, serializable: true)).to eq(email: nil, name: 'foo')
         end
+
+        it 'supports class reopening' do
+          subject.expose :name
+          child_class = Class.new(subject)
+          subject.expose :email
+
+          object = OpenStruct.new(name: 'bar', email: 'foo@bar')
+          expected = { name: 'bar', email: 'foo@bar' }
+
+          expect(subject.represent(object, serializable: true)).to eq(expected)
+          expect(child_class.represent(object, serializable: true)).to eq(expected)
+        end
       end
 
       context 'register formatters' do
@@ -290,6 +302,13 @@ class Parent < Person
           expect(child_class.formatters).to eq subject.formatters
         end
 
+        it 'inherits formatters from ancestors with reopening' do
+          child_class = Class.new(subject)
+          subject.format_with :timestamp, &date_formatter
+
+          expect(child_class.formatters).to eq subject.formatters
+        end
+
         it 'does not allow registering a formatter without a block' do
           expect { subject.format_with :foo }.to raise_error ArgumentError
         end