Strings that compare equal don't find same objects in Hash - ruby

Question

I have two strings that appear equal:
context = "Marriott International World’s Most ADMIRED Lodging Company by FORTUNE for 14th yr. via #FortuneMagazine http://cnnmon.ie/1kcFZSQ"
slice_str = context.slice(105,24) # => "http://cnnmon.ie/1kcFZSQ"
str = "http://cnnmon.ie/1kcFZSQ"
slice_str == str # => true
slice_str.eql? str # => true
But when I look up values in a hash where the keys are the strings, they do not return the same thing in Ruby 2.1.0 and Ruby 2.1.1:
redirects = {"http://cnnmon.ie/1kcFZSQ"=>""}
redirects.key?(slice_str) # => false
redirects.key?(str) # => true
What explanation is there for this behaviour? Ruby 1.9.3 works as expected.

Answer 1

This was a bug in ruby < 2.1.3
$ rvm use 2.1.2
Using /Users/richniles/.rvm/gems/ruby-2.1.2
$ irb
2.1.2 :001 > context = "Marriott International World’s Most ADMIRED Lodging Company by FORTUNE for 14th yr. via #FortuneMagazine http://cnnmon.ie/1kcFZSQ"
=> "Marriott International World’s Most ADMIRED Lodging Company by FORTUNE for 14th yr. via #FortuneMagazine http://cnnmon.ie/1kcFZSQ"
2.1.2 :002 > slice_str = context.slice(105,24) # => "http://cnnmon.ie/1kcFZSQ"
=> "http://cnnmon.ie/1kcFZSQ"
2.1.2 :003 > str = "http://cnnmon.ie/1kcFZSQ"
=> "http://cnnmon.ie/1kcFZSQ"
2.1.2 :004 > redirects = {"http://cnnmon.ie/1kcFZSQ"=>""}
=> {"http://cnnmon.ie/1kcFZSQ"=>""}
2.1.2 :005 > redirects.key?(slice_str)
=> false
2.1.2 :006 > redirects.key?(str)
=> true
but do the same in ruby 2.1.3:
$ rvm use 2.1.3
Using /Users/richniles/.rvm/gems/ruby-2.1.3
$ irb
2.1.3 :001 > context = "Marriott International World’s Most ADMIRED Lodging Company by FORTUNE for 14th yr. via #FortuneMagazine http://cnnmon.ie/1kcFZSQ"
=> "Marriott International World’s Most ADMIRED Lodging Company by FORTUNE for 14th yr. via #FortuneMagazine http://cnnmon.ie/1kcFZSQ"
2.1.3 :002 > slice_str = context.slice(105,24) # => "http://cnnmon.ie/1kcFZSQ"
=> "http://cnnmon.ie/1kcFZSQ"
2.1.3 :003 > str = "http://cnnmon.ie/1kcFZSQ"
=> "http://cnnmon.ie/1kcFZSQ"
2.1.3 :004 > redirects = {"http://cnnmon.ie/1kcFZSQ"=>""}
=> {"http://cnnmon.ie/1kcFZSQ"=>""}
2.1.3 :005 > redirects.key?(slice_str)
=> true
2.1.3 :006 > redirects.key?(str)
=> true

Answer 2

For Hash keys, its key#hash method determines, whether keys considered equal or not.
In ruby 2.1.1 for your example those two string hashes are different:
slice_str.hash == str.hash # => false in Ruby 2.1.1
Though, it's totally unclear to me, why sliced string has different hash.
Even stranger -- I've found if you test the code on ASCII-only string (your string, but with ' instead of ’) -- the hashes will be the same!
It's really weird.
The only solution I've found (though it doesn't look elegant at all):
slice_str = context.slice(105,24).chars.join # split it into separate chars and then join back
p str.hash == slice_str.hash # true now
p redirects.key?(slice_str) # true now
UPD: Oops, I haven't saw link to bug in the comments above :(