Option expose_nil doesn't work when block is passed (#329)

* Makes expose_nil option work well with blocks.

* Updated CHANGELOG.md

Co-authored-by: peter scholz <pscholz.le@gmail.com>

Author: serbiant

CHANGELOG.md

@@ -10,6 +10,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#329](https://github.com/ruby-grape/grape-entity/pull/329): Option expose_nil doesn't work when block is passed - [@serbiant](https://github.com/serbiant).
 * [#320](https://github.com/ruby-grape/grape-entity/pull/320): Gemspec: drop eol'd property rubyforge_project - [@olleolleolle](https://github.com/olleolleolle).
 * [#307](https://github.com/ruby-grape/grape-entity/pull/307): Allow exposures to call methods defined in modules included in an entity - [@robertoz-01](https://github.com/robertoz-01).
 

lib/grape_entity/exposure.rb

@@ -47,14 +47,20 @@ def compile_conditions(attribute, options)
             options[:unless]
           ].compact.flatten.map { |cond| Condition.new_unless(cond) }
 
-          unless_conditions << expose_nil_condition(attribute) if options[:expose_nil] == false
+          unless_conditions << expose_nil_condition(attribute, options) if options[:expose_nil] == false
 
           if_conditions + unless_conditions
         end
 
-        def expose_nil_condition(attribute)
+        def expose_nil_condition(attribute, options)
           Condition.new_unless(
-            proc { |object, _options| Delegator.new(object).delegate(attribute).nil? }
+            proc do |object, _options|
+              if options[:proc].nil?
+                Delegator.new(object).delegate(attribute).nil?
+              else
+                exec_with_object(options, &options[:proc]).nil?
+              end
+            end
           )
         end
 

spec/grape_entity/entity_spec.rb

@@ -126,6 +126,26 @@ def initialize(a, b, c)
               expect { subject.expose(:a, :b, :c, expose_nil: false) }.to raise_error ArgumentError
             end
           end
+
+          context 'when expose_nil option is false and block passed' do
+            it 'does not expose if block returns nil' do
+              subject.expose(:a, expose_nil: false) do |_obj, _options|
+                nil
+              end
+              subject.expose(:b)
+              subject.expose(:c)
+              expect(subject.represent(model).serializable_hash).to eq(b: nil, c: 'value')
+            end
+
+            it 'exposes is block returns a value' do
+              subject.expose(:a, expose_nil: false) do |_obj, _options|
+                100
+              end
+              subject.expose(:b)
+              subject.expose(:c)
+              expect(subject.represent(model).serializable_hash).to eq(a: 100, b: nil, c: 'value')
+            end
+          end
         end
 
         context 'when model is a hash' do