Add support to enable writing to new lines for tsv formatter

lib/fluent/plugin/formatter_tsv.rb

@@ -25,9 +25,13 @@ class TSVFormatter < Formatter
       config_param :keys, :array, value_type: :string
       desc 'The delimiter character (or string) of TSV values'
       config_param :delimiter, :string, default: "\t"
+      desc 'The parameter to enable writing to new lines'
+      config_param :add_newline, :bool, default: true
 
       def format(tag, time, record)
-        @keys.map{|k| record[k].to_s }.join(@delimiter)
+        formatted = @keys.map{|k| record[k].to_s }.join(@delimiter)
+        formatted << "\n".freeze if @add_newline
+        formatted
       end
     end
   end

test/plugin/test_formatter_tsv.rb

@@ -0,0 +1,68 @@
+require_relative '../helper'
+require 'fluent/test/driver/formatter'
+require 'fluent/plugin/formatter_tsv'
+
+class TSVFormatterTest < ::Test::Unit::TestCase
+  def setup
+    @time = event_time
+  end
+
+  def create_driver(conf = "")
+    Fluent::Test::Driver::Formatter.new(Fluent::Plugin::TSVFormatter).configure(conf)
+  end
+
+  def tag
+    "tag"
+  end
+
+  def record
+    {'message' => 'awesome', 'greeting' => 'hello'}
+  end
+
+  def test_config_params
+    d = create_driver(
+      'keys' => 'message,greeting',
+    )
+    assert_equal ["message", "greeting"], d.instance.keys
+    assert_equal "\t", d.instance.delimiter
+    assert_equal true, d.instance.add_newline
+
+    d = create_driver(
+      'keys' => 'message,greeting',
+      'delimiter' => ',',
+      'add_newline' => false,
+    )
+    assert_equal ["message", "greeting"], d.instance.keys
+    assert_equal ",", d.instance.delimiter
+    assert_equal false, d.instance.add_newline
+  end
+
+  def test_format
+    d = create_driver(
+      'keys' => 'message,greeting',
+    )
+    formatted = d.instance.format(tag, @time, record)
+
+    assert_equal("awesome\thello\n", formatted)
+  end
+
+  def test_format_without_newline
+    d = create_driver(
+      'keys' => 'message,greeting',
+      'add_newline' => false,
+    )
+    formatted = d.instance.format(tag, @time, record)
+
+    assert_equal("awesome\thello", formatted)
+  end
+
+  def test_format_with_customized_delimiters
+    d = create_driver(
+      'keys' => 'message,greeting',
+      'delimiter' => ',',
+    )
+    formatted = d.instance.format(tag, @time, record)
+
+    assert_equal("awesome,hello\n", formatted)
+  end
+end