Allow to pass empty strings and sets to .import method

lib/dynamoid/adapter_plugin/aws_sdk_v2.rb

@@ -99,7 +99,7 @@ def batch_write_item table_name, objects, options = {}
         requests = []
 
         objects.each_slice(BATCH_WRITE_ITEM_REQUESTS_LIMIT) do |os|
-          requests << os.map { |o| { put_request: { item: o } } }
+          requests << os.map { |o| { put_request: { item: sanitize_item(o) } } }
         end
 
         begin
@@ -421,13 +421,8 @@ def list_tables
       #
       # See: http://docs.aws.amazon.com/sdkforruby/api/Aws/DynamoDB/Client.html#put_item-instance_method
       def put_item(table_name, object, options = {})
-        item = {}
         options ||= {}
-
-        object.each do |k, v|
-          next if v.nil? || ((v.is_a?(Set) || v.is_a?(String)) && v.empty?)
-          item[k.to_s] = v
-        end
+        item = sanitize_item(object)
 
         begin
           client.put_item(
@@ -1037,6 +1032,12 @@ def to_h
         DELETE = 'DELETE'.freeze
         PUT    = 'PUT'.freeze
       end
+
+      def sanitize_item(attributes)
+        attributes.reject do |k, v|
+          v.nil? || ((v.is_a?(Set) || v.is_a?(String)) && v.empty?)
+        end
+      end
     end
   end
 end

spec/dynamoid/persistence_spec.rb

@@ -330,6 +330,11 @@ def reload_address
     expect(User.find(user.id).name).to eq nil
   end
 
+  it 'saves attributes with nil value' do
+    user = User.create(name: nil)
+    expect(User.find(user.id).name).to eq nil
+  end
+
   it 'supports container types being nil' do
     u = User.create(name: 'Philip')
     u.todo_list = nil
@@ -933,6 +938,8 @@ def self.name; 'Doc'; end
   describe '.import' do
     before do
       Address.create_table
+      User.create_table
+      Tweet.create_table
     end
 
     it 'creates multiple documents' do
@@ -979,5 +986,47 @@ def self.name; 'Address'; end
       expect(Dynamoid.adapter).to receive(:batch_write_item).and_call_original
       Address.import([{city: 'Chicago'}, {city: 'New York'}])
     end
+
+    it 'supports empty containers in `serialized` fields' do
+      users = User.import([name: 'Philip', favorite_colors: Set.new])
+
+      user = User.find(users[0].id)
+      expect(user.favorite_colors).to eq Set.new
+    end
+
+    it 'supports array being empty' do
+      users = User.import([{todo_list: []}])
+
+      user = User.find(users[0].id)
+      expect(user.todo_list).to eq []
+    end
+
+    it 'saves empty set as nil' do
+      tweets = Tweet.import([{group: 'one', tags: []}])
+
+      tweet = Tweet.find_by_tweet_id(tweets[0].tweet_id)
+      expect(tweet.tags).to eq nil
+    end
+
+    it 'saves empty string as nil' do
+      users = User.import([{name: ''}])
+
+      user = User.find(users[0].id)
+      expect(user.name).to eq nil
+    end
+
+    it 'saves attributes with nil value' do
+      users = User.import([{name: nil}])
+
+      user = User.find(users[0].id)
+      expect(user.name).to eq nil
+    end
+
+    it 'supports container types being nil' do
+      users = User.import([{name: 'Philip', todo_list: nil}])
+
+      user = User.find(users[0].id)
+      expect(user.todo_list).to eq nil
+    end
   end
 end