From e56d34001fd924a4b62f0c846f55174bb8c6d3c8 Mon Sep 17 00:00:00 2001
From: normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 6 Jan 2018 09:21:35 +0000
Subject: [PATCH] net/ftp: fix FrozenError in BufferedSocket

I noticed this bug while working on something else with
RUBYOPT=-d on, existing test cases all passed with it.

Note: I use String.new because it is the local style, here,
I prefer +'' (or ''.b, for a future commit)

* lib/net/ftp.rb (BufferedSocket#read): use String.new
* test/net/ftp/test_buffered_socket.rb (test_read_nil): new test
  [ruby-core:84675] [Bug #14323]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61639 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 lib/net/ftp.rb                       | 2 +-
 test/net/ftp/test_buffered_socket.rb | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/net/ftp.rb b/lib/net/ftp.rb
index ee7f029f88..c3ee47ef4d 100644
--- a/lib/net/ftp.rb
+++ b/lib/net/ftp.rb
@@ -1428,7 +1428,7 @@ module Net
           s = super(len, String.new, true)
           return s.empty? ? nil : s
         else
-          result = ""
+          result = String.new
           while s = super(DEFAULT_BLOCKSIZE, String.new, true)
             break if s.empty?
             result << s
diff --git a/test/net/ftp/test_buffered_socket.rb b/test/net/ftp/test_buffered_socket.rb
index 3cc46fa555..875c53f4e0 100644
--- a/test/net/ftp/test_buffered_socket.rb
+++ b/test/net/ftp/test_buffered_socket.rb
@@ -33,6 +33,12 @@ class BufferedSocketTest < Test::Unit::TestCase
     assert_equal("bar", sock.gets)
   end
 
+  def test_read_nil
+    sock = create_buffered_socket("foo\nbar")
+    assert_equal("foo\nbar", sock.read)
+    assert_equal("", sock.read)
+  end
+
   private
 
   def create_buffered_socket(s)