# How to debug 'ri'? **URL:** \ **Category:** ruby-talk\ **Created:** [24 July 2006 11:38 UTC](https://rubytalk.org/t/how-to-debug-ri/29234 "2006-07-24T11:38:08Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Harold\_Hausman](https://avatars.discourse-cdn.com/v4/letter/h/ac91a4/32.png) [@Harold\_Hausman](https://rubytalk.org/u/Harold_Hausman)\ **Post date:** [24 July 2006 11:38 UTC](https://rubytalk.org/t/how-to-debug-ri/29234/1 "2006-07-24T11:38:08Z")
I'm seeing this all of a sudden: C:\\>ri Dir c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb:99:in `concat': can't convert nil into Array (TypeError)         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb:99:in `merge\_in'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_reader.rb:56:in `get\_class'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_reader.rb:52:in `get\_class'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:70:in `report\_class\_stuff'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:106:in `get\_info\_for'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:135:in `process\_args'         from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:134:in `process\_args'         from c:/ruby/bin/ri.bat:55 :(, it crashes fxri also if I type 'Dir' into the search box. Kind thanks in advance for any insight, -Harold ---
**Author:** ![Garance\_A\_Drosehn](https://avatars.discourse-cdn.com/v4/letter/g/ccd318/32.png) [@Garance\_A\_Drosehn](https://rubytalk.org/u/Garance_A_Drosehn)\ **Post date:** [26 July 2006 18:16 UTC](https://rubytalk.org/t/how-to-debug-ri/29234/2 "2006-07-26T18:16:45Z")
I am not seeing that problem on my unix box, but that does not mean much... If you have write access to the files installed by ruby, then you can debug 'ri' just like any other script. I've done it in the past, with obscure bugs in 'ri' that only happened with a few specific requests. I'd save a copy of:      c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb and then change the merge\_in function to add a few printf statements. Takes a little trial and error, but it's certainly doable. I assume your file looks something like:       if @comment.nil? || @comment.empty?         @comment = old.comment       else         @comment \<\< SM::Flow::RULE.new         @comment.concat old.comment # \<- line 99       end so I'd add some printf statements around there to see what is going on with @comment and old.comment. > **···** > > On 7/24/06, Harold Hausman \ wrote: > > > I'm seeing this all of a sudden: > > C:\\>ri Dir > > c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb:99:in `concat': can't > > convert nil into Array (TypeError) > > -- > Garance Alistair Drosehn = drosihn@gmail.com > Senior Systems Programmer > Rensselaer Polytechnic Institute; Troy, NY; USA ---
**Author:** ![Eric\_Hodel1](https://avatars.discourse-cdn.com/v4/letter/e/a9adbd/32.png) [@Eric\_Hodel1](https://rubytalk.org/u/Eric_Hodel1)\ **Post date:** [29 July 2006 02:04 UTC](https://rubytalk.org/t/how-to-debug-ri/29234/3 "2006-07-29T02:04:42Z")
This is fixed in 1.8.5p1 > **···** > > On Jul 24, 2006, at 4:38 AM, Harold Hausman wrote: > > > I'm seeing this all of a sudden: > > C:\\>ri Dir > > c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb:99:in `concat': can't > > convert nil into Array (TypeError) > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_descriptions.rb:99:in `merge\_in' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_reader.rb:56:in `get\_class' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_reader.rb:52:in `get\_class' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:70:in > > `report\_class\_stuff' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:106:in `get\_info\_for' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:135:in `process\_args' > >        from c:/ruby/lib/ruby/1.8/rdoc/ri/ri\_driver.rb:134:in `process\_args' > >        from c:/ruby/bin/ri.bat:55 > > > > :(, it crashes fxri also if I type 'Dir' into the search box. > > > > Kind thanks in advance for any insight, > > -- > Eric Hodel - drbrain@segment7.net - [http://blog.segment7.net](http://blog.segment7.net) > This implementation is HODEL-HASH-9600 compliant > > [http://trackmap.robotcoop.com](http://trackmap.robotcoop.com)