:only/:except options for expose

lib/grape_entity/entity.rb

@@ -187,15 +187,12 @@ def self.inherited(subclass)
     #   field, typically the value is a hash with two fields, type and desc.
     # @option options :merge This option allows you to merge an exposed field to the root
     #
-    # rubocop:disable Layout/LineLength
     def self.expose(*args, &block)
       options = merge_options(args.last.is_a?(Hash) ? args.pop : {})
 
-      if args.size > 1
-
-        raise ArgumentError, 'You may not use the :as option on multi-attribute exposures.' if options[:as]
-        raise ArgumentError, 'You may not use the :expose_nil on multi-attribute exposures.' if options.key?(:expose_nil)
-        raise ArgumentError, 'You may not use block-setting on multi-attribute exposures.' if block_given?
+      ensure_multi_attrs_options_valid!(args, options)
+      if (options.key?(:only) || options.key?(:except)) && !options.key?(:using)
+        raise ArgumentError, 'You cannot use the :only/:except without :using.'
       end
 
       if block_given?
@@ -214,7 +211,15 @@ def self.expose(*args, &block)
       @nesting_stack ||= []
       args.each { |attribute| build_exposure_for_attribute(attribute, @nesting_stack, options, block) }
     end
-    # rubocop:enable Layout/LineLength
+
+    def self.ensure_multi_attrs_options_valid!(args, options)
+      return if args.size < 2
+      raise ArgumentError, 'You may not use the :as option on multi-attribute exposures.' if options[:as]
+      raise ArgumentError, 'You may not use the :expose_nil on multi-attribute exposures.' if options.key?(:expose_nil)
+      raise ArgumentError, 'You may not use the :only on multi-attribute exposures.' if options.key?(:only)
+      raise ArgumentError, 'You may not use the :except on multi-attribute exposures.' if options.key?(:except)
+      raise ArgumentError, 'You may not use block-setting on multi-attribute exposures.' if block_given?
+    end
 
     def self.build_exposure_for_attribute(attribute, nesting_stack, options, block)
       exposure_list = nesting_stack.empty? ? root_exposures : nesting_stack.last.nested_exposures
@@ -585,6 +590,8 @@ def to_xml(options = {})
       merge
       expose_nil
       override
+      only
+      except
     ].to_set.freeze
 
     # Merges the given options with current block options.

lib/grape_entity/exposure/base.rb

@@ -4,7 +4,7 @@ module Grape
   class Entity
     module Exposure
       class Base
-        attr_reader :attribute, :is_safe, :documentation, :override, :conditions, :for_merge
+        attr_reader :attribute, :is_safe, :documentation, :override, :conditions, :for_merge, :only, :except
 
         def self.new(attribute, options, conditions, *args, &block)
           super(attribute, options, conditions).tap { |e| e.setup(*args, &block) }
@@ -20,6 +20,8 @@ def initialize(attribute, options, conditions)
           @attr_path_proc = options[:attr_path]
           @documentation = options[:documentation]
           @override = options[:override]
+          @only = options[:only]
+          @except = options[:except]
           @conditions = conditions
         end
 

lib/grape_entity/exposure/represent_exposure.rb

@@ -23,7 +23,7 @@ def ==(other)
         end
 
         def value(entity, options)
-          new_options = options.for_nesting(key(entity))
+          new_options = options.for_nesting(key(entity)).with_expose(self)
           using_class.represent(@subexposure.value(entity, options), new_options)
         end
 

lib/grape_entity/options.rb

@@ -31,6 +31,19 @@ def merge(new_opts)
         Options.new(merged)
       end
 
+      def with_expose(expose)
+        opts_only_ary = Array(self[:only])
+        opts_except_ary = Array(self[:except])
+
+        only_ary = Array(expose.only)
+        except_ary = Array(expose.except)
+
+        merge(
+          only: opts_only_ary.any? || only_ary.any? ? opts_only_ary | only_ary : nil,
+          except: opts_except_ary.any? || except_ary.any? ? opts_except_ary | except_ary : nil
+        )
+      end
+
       def reverse_merge(new_opts)
         return self if new_opts.empty?
 

spec/grape_entity/entity_spec.rb

@@ -25,8 +25,28 @@
       context 'option validation' do
         it 'makes sure that :as only works on single attribute calls' do
           expect { subject.expose :name, :email, as: :foo }.to raise_error ArgumentError
+        end
+        it do
           expect { subject.expose :name, as: :foo }.not_to raise_error
         end
+        it do
+          expect { subject.expose :name, :email, only: [:name], using: 'SomeEntity' }.to raise_error ArgumentError
+        end
+        it do
+          expect { subject.expose :name, only: [:name], using: 'SomeEntity' }.not_to raise_error
+        end
+        it do
+          expect { subject.expose :name, :email, except: [:name], using: 'SomeEntity' }.to raise_error ArgumentError
+        end
+        it do
+          expect { subject.expose :name, except: [:name], using: 'SomeEntity' }.not_to raise_error
+        end
+        it do
+          expect { subject.expose :name, only: [:name] }.to raise_error ArgumentError
+        end
+        it do
+          expect { subject.expose :name, except: [:name] }.to raise_error ArgumentError
+        end
 
         it 'makes sure that :format_with as a proc cannot be used with a block' do
           # rubocop:disable Style/BlockDelimiters
@@ -1680,6 +1700,36 @@ class FriendEntity < Grape::Entity
           expect(rep.last.serializable_hash[:name]).to eq 'Friend 2'
         end
 
+        it 'exposes only the specified fields' do
+          module EntitySpec
+            class FriendEntity < Grape::Entity
+              expose :name, :email
+            end
+          end
+
+          fresh_class.class_eval do
+            expose :friends, using: EntitySpec::FriendEntity, only: [:name]
+          end
+          rep = subject.value_for(:friends)
+          expect(rep.first.serializable_hash).to eq(name: 'Friend 1')
+          expect(rep.last.serializable_hash).to eq(name: 'Friend 2')
+        end
+
+        it 'exposes except the specified fields' do
+          module EntitySpec
+            class FriendEntity < Grape::Entity
+              expose :name, :email
+            end
+          end
+
+          fresh_class.class_eval do
+            expose :friends, using: EntitySpec::FriendEntity, except: [:email]
+          end
+          rep = subject.value_for(:friends)
+          expect(rep.first.serializable_hash).to eq(name: 'Friend 1')
+          expect(rep.last.serializable_hash).to eq(name: 'Friend 2')
+        end
+
         it 'passes through the proc which returns an array of objects with custom options(:using)' do
           module EntitySpec
             class FriendEntity < Grape::Entity