Static Analysis with ruby-lint

A lightning talk at the 2016-11-10 Prague Ruby Meetup

Transcript

1. Static Analysis with ruby-lint Martin Vidner, @mvidner 2016-11-10
2. Problem • stupid bugs – misspelled identifier – too many/few arguments – missing namespace – wrong receiver for method – sloppy refactoring
3. Context • Team: YaST • SUSE installer + config tool • ~500,000 lines of Ruby
4. Solution • Static analysis of code • "No can do - Ruby is dynamic" • Still, there is much code that contains no metaprogramming magic and can be analyzed • ruby-lint.gem
5. Example Input
6. Example Output • ruby-lint-readme.rb: warning: line 2, column 18: unused argument name • ruby-lint-readme.rb: error: line 7, column 22: undefined instance variable @name • ruby-lint-readme.rb: warning: line 12, column 1: unused local variable greeting • ruby-lint-readme.rb: error: line 14, column 1: wrong number of arguments for 'greet' (expected 0 but got 1)
7. And they linted happily ever after
8. And they linted happily ever after • Right?
9. And they linted happily ever after • Right? • Wrong • There are false positives
10. And they linted happily ever after • Right? • Wrong • There are false positives • Thousands of false positives for every actual bug found
11. Alternatives?
12. Alternatives? • Write tests
13. Alternatives? • Write tests • Use RuboCop
14. Alternatives? • Write tests • Use RuboCop • Type Hints
15. Alternatives? • Write tests • Use RuboCop • Type Hints PEP484 oops, that's Python
16. Alternatives? • Write tests • Use RuboCop • Type Hints PEP484 oops, that's Python • Duck inference Ruby 3
17. Alternatives? • Write tests • Use RuboCop • Type Hints PEP484 oops, that's Python • Duck inference Ruby 3 „you have to wait for years“ (matz, 2016-09)
18. Alternatives? • Write tests • Use RuboCop • Type Hints PEP484 oops, that's Python • Duck inference Ruby 3 „you have to wait for years“ (matz, 2016-09) • Fix ruby-lint
19. Alternatives? • What do you do?
20. We're Hiring • https://jobs.suse.com – Ruby / C++ hero/heroine – Ruby / C++ enthusiast – and 63 more