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ActiveSupport::Multibyte::Chars#gsub fails while String#gsub works

#3475

>> s = "Hybrid Companies and the Future of the Economy: An Interview with Criteri&#8230;"
=> "Hybrid Companies and the Future of the Economy: An Interview with Criteri&#8230;"
>> require 'cgi'
=> true
>> CGI.escape(s)
=> "Hybrid+Companies+and+the+Future+of+the+Economy%3A+An+Interview+with+Criteri%26%238230%3B"
>> require 'activesupport'
=> true
>> s = ActiveSupport::Multibyte::Chars.new "Hybrid Companies and the Future of the Economy: An Interview with Criteri&#8230;"
=> #<ActiveSupport::Multibyte::Chars:0x1017be2e0 @wrapped_string="Hybrid Companies and the Future of the Economy: An Interview with Criteri&#8230;">
>> CGI.escape(s)
NoMethodError: undefined method `size' for nil:NilClass
    from /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/1.8/cgi.rb:343:in `escape'
    from /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/gems/1.8/gems/activesupport-2.3.4/lib/active_support/multibyte/chars.rb:100:in `gsub'
    from /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/gems/1.8/gems/activesupport-2.3.4/lib/active_support/multibyte/chars.rb:100:in `__send__'
    from /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/gems/1.8/gems/activesupport-2.3.4/lib/active_support/multibyte/chars.rb:100:in `method_missing'
    from /opt/ruby-enterprise-1.8.7-2009.10/lib/ruby/1.8/cgi.rb:342:in `escape'

Reported by Mike Perham · November 10th, 2009 @ 03:35 AM

Activity

Norman Clarke

The problem here is that CGI.escape relies on the $1 variable, to get the last regexp match:

# cgi.rb:341
def CGI::escape(string)
  string.gsub(/([^ a-zA-Z0-9_.-]+)/n) do
    '%' + $1.unpack('H2' * $1.size).join('%').upcase
  end.tr(' ', '+')
end

ActiveSupport::Multibyte::Chars invokes #gsub on a wrapped_string using method_missing.

# chars.rb:96
# Forward all undefined methods to the wrapped string.
def method_missing(method, *args, &block)
  if method.to_s =~ /!$/
    @wrapped_string.__send__(method, *args, &block)
    self
  else
    result = @wrapped_string.__send__(method, *args, &block)
    p $1
    result.kind_of?(String) ? chars(result) : result
  end
end

Now here's the real problem. Surprisingly, when you return from a function in Ruby, the value of the $1 variable is cleared:

$ cat temp.rb
def test_gsub
  result = "a".gsub(/(a)/, "b")
  p $1
  result
end

test_gsub
p $1

$ ruby temp.rb
"a"
nil

So I don't think there's any decent way to fix this in ActiveSupport, ideally the fix would go in CGI.

As a simple workaround, I suggest you simply do this:

CGI.escape(s.to_s)

April 13th, 2010 @ 02:50 PM

Santiago Pastorino
- State changed from new to open
This issue has been automatically marked as stale because it has not been commented on for at least three months.

The resources of the Rails core team are limited, and so we are asking for your help. If you can still reproduce this error on the 3-0-stable branch or on master, please reply with all of the information you have about it and add "[state:open]" to your comment. This will reopen the ticket for review. Likewise, if you feel that this is a very important feature for Rails to include, please reply with your explanation so we can consider it.

Thank you for all your contributions, and we hope you will understand this step to focus our efforts where they are most helpful.

February 2nd, 2011 @ 04:50 PM
Santiago Pastorino
- State changed from open to stale
February 2nd, 2011 @ 04:50 PM
bingbing
omega watch

March 26th, 2011 @ 01:36 AM