[ruby/logger] Let File::NULL ("/dev/null", "NUL" etc.) be considered a nil log device

https://github.com/ruby/logger/commit/b42a1b99aa

lib/logger.rb

@@ -385,7 +385,7 @@ class Logger
     self.datetime_format = datetime_format
     self.formatter = formatter
     @logdev = nil
-    if logdev
+    if logdev && logdev != File::NULL
       @logdev = LogDevice.new(logdev, shift_age: shift_age,
         shift_size: shift_size,
         shift_period_suffix: shift_period_suffix,

test/logger/test_logger.rb

@@ -378,4 +378,9 @@ class TestLogger < Test::Unit::TestCase
     log = log(logger, :debug) { "msg" }
     assert_nil log.msg
   end
+
+  def test_does_not_instantiate_log_device_for_File_NULL
+    l = Logger.new(File::NULL)
+    assert_nil(l.instance_variable_get(:@logdev))
+  end
 end