Ruby Debugging - Presented at the Montreal.rb meeting on March 20th 2012

1. The ultimate
guide to ruby
debugging
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

2. The ultimate
guide to ruby
debugging
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

3. Ruby debugging
basics
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

4. About me
More on that later

5. Why?
● TDD won't save you all the time
● Understand untested, legacy, complicated
code
● Understand unexpected behavior
● Interactive coding

6. Why?
● "When I coded in Delphi 2 I had support for it
on my IDE"

7. How?
●
●
●
●
Stack traces
puts, p, pp
Logging
debug module
● ruby-debug
○ ruby-debug19
● Pry
○ pry-nav
○ pry-stack_explorer

8. How?
●
●
●
●
Stack traces
puts, p, pp
Logging
debug module
● ruby-debug
○ ruby-debug19
● Pry
○ pry-nav
○ pry-stack_explorer

9. ruby-debug
Created by Kent Sibilev and Rocky Bernstein
● https://github.com/ruby-debug/ruby-debug
● http://bashdb.sourceforge.net/ruby-debug.
html
ruby-debug19 is a port by Mark Moseley

10. ruby-debug for 1.8.7
1. gem install ruby-debug
2. profit

11. ruby-debug for 1.9.x
1. gem install ruby-debug19
2. profit (almost)
● Workaround for 1.9.3:
○ Need newer versions for linecache and ruby-debugbase, not on rubygems
○ Some stuff is still broken
○ https://gist.github.com/2047760
○ Thanks to @fredostarr, @spastorino, @rafaeldx7
and @garyharan

12. ruby-debug
●
●
●
●
●
●
Follow the code execution
Inspect objects
Set breakpoints
See the stack
Change state (be careful)
Debug remotely

13. ruby-debug demo
● Lots of commands
○
○
○
○
○
○
●
debugger, rdebug
list, help, quit
p, pp, ps, display, info
break, next, step, continue
disable, condition
irb, where, edit, set, show
Fingers crossed

14. ruby-debug demo
Live demos always go wrong
Sorry in advance :)

15. Pry

16. Pry
● Developed by John Mair (@banisterfiend)
● http://github.com/pry/pry
● Started as a turbo irb
● An ecosystem is growing around it
○ Lots of plugins

17. Pry
● gem install pry
● gem install pry-doc

18. Pry demo
● Nice features
○
○
○
○
pagination
autocomplete
syntax highlight
highly customizable
● Lots of commands and features
○
○
○
○
●
●
ls, ls --help
cd, nesting, exit
.commands
show-doc, show-method, edit-method
pry-nav is not ready for primetime
pry-stack_explorer is ok

19. Lessons learned
● Debugging is not a bad thing when used
properly and sparingly
● Basic tools solve ~ 90% of the issues
● BDD/TDD will save you from debugging
most of the time
● The future is quite cloudy for Ruby debug
tools:
○ https://github.com/rocky/rb-trepanning
○ Cross-implementation?
○ http://blog.bithug.org/2011/09/maglev-debug

20. References - ruby-debug
● http://bashdb.sourceforge.net/ruby-debug.html
● http://railscasts.com/episodes/54-debugging-with-ruby●
●
●
●
debug
http://guides.rubyonrails.
org/debugging_rails_applications.html
https://github.com/ruby-debug
https://github.com/mark-moseley/ruby-debug/
https://gist.github.com/2047760

21. References - Pry
● http://pry.github.com
● https://github.com/pry
● http://banisterfiend.wordpress.com/2012/02/14/the-pry●
●
●
ecosystem/
http://pry.github.com/screencasts.html
○ Special thanks to @fnando :)
http://railscasts.com/episodes/280-pry-with-rails
http://twitter.com/banisterfiend

22. Questions
?
I just need 5 more minutes after this :)

23. About me
http://flagwallpapers.com/water-color-brazilian-

24. About me
● Coding professionally for 16 years
● Agilist, product and community guy too
● I love Ruby
"Ruby is designed to make programmers
happy"
- Matz

25. About me

26. About me

27. Ruby community in Brazil
40 to 60 people every month

28. Ruby community in Brazil
https://picasaweb.google.com/105291946909431816672

29. Ruby community in Brazil
https://picasaweb.google.com/105291946909431816672

30. Ruby community in Brazil
http://groups.google.com/group/dojo_sp

31. Ruby community in Brazil
http://pothix.com/blog/events/encontro-de-numero-5-do-guru-

32. Ruby community in Brazil
http://blog.lambda3.com.br/2012/02/dojo-dojo-

33. Ruby community in Brazil
~ 1,500 attendees, this year will be the 5th edition
http://www.flickr.

34. Ruby community in Brazil
~ 1,500 attendees, this year will be the 5th edition
http://www.flickr.

35. Ruby community in Brazil
Everybody is invited - August 30 and 31 2012 - São Paulo
http://www.flickr.

36. Thank you
Merci :)
@rafaelrosafu
rrosa@iweb.com
rafaelrosafu@gmail.com
grokpodcast.com
linkedin.com/in/rafaelrosafu