Fix bug of Tempfile#size if nothing is written [Bug #13198]

* lib/tempfile.rb (Tempfile#size): Fix its behavior when nothing
  is written. Tempfile#size should return 0 in this case.
  The patch is from nobu <nobu@ruby-lang.org>.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57972 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/tempfile.rb

@@ -227,7 +227,7 @@ class Tempfile < DelegateClass(File)
     if !@tmpfile.closed?
       @tmpfile.size # File#size calls rb_io_flush_raw()
     else
-      File.size?(@tmpfile.path)
+      File.size(@tmpfile.path)
     end
   end
   alias length size

test/test_tempfile.rb

@@ -247,6 +247,13 @@ puts Tempfile.new('foo').path
     assert_equal 5, t.size
   end
 
+  def test_size_on_empty_file
+    t = tempfile("foo")
+    t.write("")
+    t.close
+    assert_equal 0, t.size
+  end
+
   def test_concurrency
     threads = []
     tempfiles = []