The joy of Ruby Debugging - Pry Universe

Let's be honest, in typical programming world debugging is a pain in the ass. `printf` everywhere, rerun the code every time... Such a waste of time.

But Ruby... Ruby is different, is such a great language for introspection and live code analysis. Here's where Pry shines. During this talk we will meet Pry alongside some other tool in his universe, like `pry-rescue`, `pry-stack_explorer` and we will see how debugging a simple Ruby script or a large RubyOnRails application is easy, and fun!

Transcript

1. Pry as IRB replacement Pry real magic The joy of ruby debugging Enrico Carlesso coders51 October 2015 Enrico Carlesso Pry universe 1/18
2. Pry as IRB replacement Pry real magic Me Enrico Carlesso I spin on red things Enrico Carlesso Pry universe 2/18
3. Pry as IRB replacement Pry real magic Company :( Enrico Carlesso Pry universe 3/18
4. Pry as IRB replacement Pry real magic Debugging is boring Typical debugging worflow 1 Find in the backtrace the relevant file and line 2 Add some random puts (and inspect) 3 Rerun code (at least we don’t need to compile) 4 Change some code 5 Rerun 6 If you are very very lucky, move forward (likely forgetting puts around), if not iterate from number 3 Enrico Carlesso Pry universe 4/18
5. Pry as IRB replacement Pry real magic Ruby! Then we remember: • Ruby is a scripting language • Introspection • Reflection • Metaprogramming • Someone maybe has put all this together? Enrico Carlesso Pry universe 5/18
6. Pry as IRB replacement Pry real magic Pry! Enrico Carlesso Pry universe 6/18
7. Pry as IRB replacement Pry real magic Pry! Pry is a powerful alternative to the standard IRB shell for Ruby. It features syntax highlighting, a flexible plugin architecture, runtime invocation and source and documentation browsing. from http://pryrepl.org Enrico Carlesso Pry universe 6/18
8. Pry as IRB replacement Pry real magic What is a REPL? • Read • Evaluate • Print • Loop Enrico Carlesso Pry universe 7/18
9. Pry as IRB replacement Pry real magic What is a REPL? • Read • Evaluate • Print • Loop def repl loop { puts eval $stdin.readline } end Enrico Carlesso Pry universe 7/18
10. Pry as IRB replacement Pry real magic Pry cool stuff • Syntax Highlighting • Tab Completion • _ and __ Enrico Carlesso Pry universe 8/18
11. Pry as IRB replacement Pry real magic Source code is the best documentation • ? show-doc • $ show-source • ls • cd Enrico Carlesso Pry universe 9/18
12. Pry as IRB replacement Pry real magic Source code is the best documentation • ? show-doc • $ show-source • ls • cd • edit Enrico Carlesso Pry universe 9/18
13. Pry as IRB replacement Pry real magic binding.pry binding.pry Anywhere in the code will stop the execution and open a REPL instance right there, with all local bindings. Enrico Carlesso Pry universe 10/18
14. Pry as IRB replacement Pry real magic But what can we do? • Access to all local variables at present state • see documentation and source of relevant methods • whereami • play -l Enrico Carlesso Pry universe 11/18
15. Pry as IRB replacement Pry real magic Plugins • pry-remote • pry-byebug (up and down!) pry-stack_explorer • pry-inline • pry-rescue Enrico Carlesso Pry universe 12/18
16. Pry as IRB replacement Pry real magic Let’s see something DEMO! Enrico Carlesso Pry universe 13/18
17. Pry as IRB replacement Pry real magic Pry::Commands.block_command In your ~/.pryrc Pry::Commands.block_command "silence_arecord", "Suppress ActiveRecord output" do ActiveRecord::Base.logger = nil end Pry::Commands.block_command "arecord_to_stdout", "Redirects ActiveRecord output to standard output" do ActiveRecord::Base.logger = Logger.new(STDOUT) end Enrico Carlesso Pry universe 14/18
18. Pry as IRB replacement Pry real magic Pry::Commands.block_command In your ~/.pryrc Pry::Commands.block_command "silence_arecord", "Suppress ActiveRecord output" do ActiveRecord::Base.logger = nil end Pry::Commands.block_command "arecord_to_stdout", "Redirects ActiveRecord output to standard output" do ActiveRecord::Base.logger = Logger.new(STDOUT) end Not enough? Enrico Carlesso Pry universe 14/18
19. Pry as IRB replacement Pry real magic Pry::Commands.create_command Pry::Commands.create_command "echo" do description "Echo the input: echo [ARGS]" def process output.puts args.join(" ") end end This will provide a full Pry::Commands instance Enrico Carlesso Pry universe 15/18
20. Pry as IRB replacement Pry real magic Repl Driven Development • Run the code • Read the code • Understand the code Enrico Carlesso Pry universe 16/18
21. Pry as IRB replacement Pry real magic Repl Driven Development • Run the code (takes seconds) • Read the code (takes minutes) • Understand the code (takes weeks? life?) Enrico Carlesso Pry universe 17/18
22. Pry as IRB replacement Pry real magic One big thing Use Pry Enrico Carlesso Pry universe 18/18
23. Pry as IRB replacement Pry real magic THANKS! Enrico Carlesso Pry universe 19/18