Marshal load loses correct encoding for string subclass #939
Description
I am getting unexpected behavior when using Marshal.load on a subclass of string that includes an instance variable with a value. In the example below the instance variable is an integer, but it seems to do this with anything other than nil for the instance variable.
Note that Marshal.dump seems to yield identical output in JRuby and MRI (the encoding of the Marshal.dump string is ASCII-8BIT in both cases as expected)
This problem was encountered in a Rails app after attempting to cache an object containing an object with a subclass of string.
The workaround I am using is to customize marshal_dump on the class to return an array with the string data as one element and the ivars as the other.
jruby 1.7.5.dev (1.9.3p392) 2013-08-02 c672591 on Java HotSpot(TM) 64-Bit Server VM 1.7.0_25-b15 [linux-amd64]
[1] pry(main)> class StringSubclass < String
[1] pry(main)* attr_accessor :oops
[1] pry(main)* end
=> nil
[2] pry(main)> s_ok = StringSubclass.new('what')
=> "what"
[3] pry(main)> s_ok.encoding
=> #<Encoding:UTF-8>
[4] pry(main)> Marshal.dump(s_ok)
=> "\x04\bIC:\x13StringSubclass\"\twhat\x06:\x06ET"
[5] pry(main)> Marshal.load(Marshal.dump(s_ok)).encoding
=> #<Encoding:UTF-8>
[6] pry(main)>
[7] pry(main)> s_oops = StringSubclass.new('what').tap { |s| s.oops = 1; s }
=> "what"
[8] pry(main)> s_oops.encoding
=> #<Encoding:UTF-8>
[9] pry(main)> Marshal.dump(s_oops)
=> "\x04\bIC:\x13StringSubclass\"\twhat\a:\x06ET:\n@oopsi\x06"
[10] pry(main)> Marshal.load(Marshal.dump(s_oops)).encoding
=> #<Encoding:ASCII-8BIT>
ruby 2.0.0p195 (2013-05-14 revision 40734) [x86_64-linux]
[1] pry(main)> class StringSubclass < String
[1] pry(main)* attr_accessor :oops
[1] pry(main)* end
=> nil
[2] pry(main)> s_ok = StringSubclass.new('what')
=> "what"
[3] pry(main)> s_ok.encoding
=> #<Encoding:UTF-8>
[4] pry(main)> Marshal.dump(s_ok)
=> "\x04\bIC:\x13StringSubclass\"\twhat\x06:\x06ET"
[5] pry(main)> Marshal.load(Marshal.dump(s_ok)).encoding
=> #<Encoding:UTF-8>
[6] pry(main)>
[7] pry(main)> s_oops = StringSubclass.new('what').tap { |s| s.oops = 1; s }
=> "what"
[8] pry(main)> s_oops.encoding
=> #<Encoding:UTF-8>
[9] pry(main)> Marshal.dump(s_oops)
=> "\x04\bIC:\x13StringSubclass\"\twhat\a:\x06ET:\n@oopsi\x06"
[10] pry(main)> Marshal.load(Marshal.dump(s_oops)).encoding
=> #<Encoding:UTF-8>