Add new store_attribute_with_nil_value config option

Author: andrykonchin

lib/dynamoid/adapter_plugin/aws_sdk_v3.rb

@@ -639,8 +639,12 @@ def self.attribute_value_list(operator, value)
       end
 
       def sanitize_item(attributes)
+        config_value = Dynamoid.config.store_attribute_with_nil_value
+        store_attribute_with_nil_value = config_value.nil? ? false : !!config_value
+
         attributes.reject do |_, v|
-          v.nil? || ((v.is_a?(Set) || v.is_a?(String)) && v.empty?)
+          ((v.is_a?(Set) || v.is_a?(String)) && v.empty?) ||
+            (!store_attribute_with_nil_value && v.nil?)
         end.transform_values do |v|
           v.is_a?(Hash) ? v.stringify_keys : v
         end

lib/dynamoid/config.rb

@@ -31,6 +31,7 @@ module Config
     option :sync_retry_max_times, default: 60 # a bit over 2 minutes
     option :sync_retry_wait_seconds, default: 2
     option :convert_big_decimal, default: false
+    option :store_attribute_with_nil_value, default: false # keep or ignore attribute with nil value at saving
     option :models_dir, default: './app/models' # perhaps you keep your dynamoid models in a different directory?
     option :application_timezone, default: :utc # available values - :utc, :local, time zone name like "Hawaii"
     option :dynamodb_timezone, default: :utc # available values - :utc, :local, time zone name like "Hawaii"

spec/dynamoid/persistence_spec.rb

@@ -695,6 +695,43 @@ def reload_address
         end
       end
     end
+
+    describe '`store_attribute_with_nil_value` config option' do
+      let(:klass) do
+        new_class do
+          field :age, :integer
+        end
+      end
+
+      context 'true', config: { store_attribute_with_nil_value: true } do
+        it 'keeps document attribute with nil' do
+          obj = klass.new(age: nil)
+          obj.save
+
+          expect(raw_attributes(obj)).to include(age: nil)
+        end
+      end
+
+      context 'false', config: { store_attribute_with_nil_value: false } do
+        it 'does not keep document attribute with nil' do
+          obj = klass.new(age: nil)
+          obj.save
+
+          # doesn't contain :age key
+          expect(raw_attributes(obj).keys).to contain_exactly(:id, :created_at, :updated_at)
+        end
+      end
+
+      context 'by default', config: { store_attribute_with_nil_value: nil } do
+        it 'does not keep document attribute with nil' do
+          obj = klass.new(age: nil)
+          obj.save
+
+          # doesn't contain :age key
+          expect(raw_attributes(obj).keys).to contain_exactly(:id, :created_at, :updated_at)
+        end
+      end
+    end
   end
 
   describe '#update_attribute' do