Suppress Warning

https://docs.google.com/presentation/d/1baj2LEmSceqXR7fsjwT4l9leT6uMAvCcLX9olyYaOAg/edit?usp=sharing

Transcript

1. Suppress Warnings 15th, Sep. 2019 大阪Ruby会議02
2. pp self • Masataka “Pocke” Kuwabara • I’m from https://ruby-jp.github.io! • Works for Bit Journey, Inc. / Kibela • https://github.com/pocke • https://twitter.com/p_ck_
3. Recently we released Kibela Web API https://prtimes.jp/main/html/rd/p/000000008.000024220.html
4. Goal of this talk • You can: ◦ Find bugs with warnings. ◦ Reduce warnings from your applications. ◦ Create patches to OSS to suppress warnings.
5. Introduce Warning
6. What is the warning? • Ruby warns code, if ◦ It may have a bug. ◦ It is deprecated. • For example: ◦ Useless variable: x = 1; p y ◦ Deprecated method: File.exists? ▪ Use File.exist? instead.
7. Warning levels • Ruby has 3 levels for warning. • Level 0: All warnings are disabled. • Level 1: Only important warnings are enabled (default). • Level 2: All warnings are enabled. ◦ Almost warnings are enabled only with Level 2.
8. How to enable all warnings • `-w` option enables all warnings. ◦ The level 2 • $ ruby -e 42 ◦ Print nothing • $ ruby -w -e 42 ◦ -e:1: warning: possibly useless use of a literal in void context
9. Enable warnings without CLI option • We can also use RUBYOPT environment variable. • RUBYOPT is parsed as Ruby’s command line option. • RUBYOPT=-w bin/rails s • $ echo ‘export RUBYOPT=”-w”’ >> ~/.bashrc
10. What can we do with warning?
11. With warning, we can: • We can find bugs with warning. • We can contribute to OSS easier.
12. Find bugs • Ruby warns possible bug code. • If you solve a warning, a bug may be solved.
13. Contribute to OSS easier • Warning is easy to fix, in many cases. • Because ◦ The goal is clear. ◦ The patch will be small. • But some warnings is difficult to fix. e.g. ◦ Uninitialized instance variable ◦ The code has bug(s).
14. Why should we fix warnings?
15. Why should we fix warnings? • We can find bugs with warnings. • But if application has too many warnings, it is too difficult. • Similar with “Broken Windows Theory”.
17. Warning examples
18. Warnings examples • Let’s look warning with real pull requests. ◦ Warning meaning. ◦ How to fix warning. ◦ What problems is found by the warning.
19. Deprecated method cookpad/rrrspec#76
20. Deprecated method • File.exists?(path) ◦ File.exists? is a deprecated name, use File.exist? instead • Dir.exists?(path) ◦ Dir.exists? is a deprecated name, use Dir.exist? instead Let’s look the pull request!
21. •
22. Part of the patch - unless Dir.exists?(packaging_dir) + unless Dir.exist?(packaging_dir)
23. Overview • File.exists? and Dir.exists? are deprecated. • It should be replaced with File.exist?. • It does not change any behavior.
24. It is one of the easiest warning! • Good for first step of pull request! • Because ◦ Fixing approach is obvious. ◦ It does not change any behavior. • But it has only small impact.
25. Other deprecated methods • Kernel.#open for URI. (In Ruby 2.7.0-dev) ◦ Use URI.open. ▪ File.open, IO.open, and IO.popen are also avairable. • URI.escape ◦ Use ERB::Util.#url_encode, CGI.escape, or URI.encode_www_form_component ◦ It depends on the requirement.
26. Method redefined whitequark/parser#378
27. Method Redefined • def foo; end # It is ignored def foo; end ◦ warning: method redefined; discarding old foo Let’s look the pull request!
29. Patch
30. Overview • Two methods ware accidently redefined in minitest test file. • A method has the same content, so I removed it. • But the other one has different method body.
31. In another case • If you really want to redefine method, use remove_method. ◦ remove_method :foo def foo; end ◦ e.g. https://github.com/ruby/irb/pull/18
32. duplicated when clause thoughtbot/capybara-webkit#1068
33. Duplicated when clause • case x when 1, 2, 1 end ◦ duplicated `when' clause with line 2 is ignored
35. Part of the patch
36. Character class has duplicated range rouge-ruby/rouge#1197
37. Character class has duplicated range • /[aa]/ ◦ “a” is duplicated. • /[\w_]/ ◦ “\w” includes “_”. • /[\s\n]/ ◦ “\s” includes new line. • /[*+-=]/ ◦ It means “*” and chars between “+” and “=”.
40. Part of the patch (1)
41. Part of the patch (2)
42. Part of the patch (3)
43. Overview • Ruby also warns Regexp. • In this pull request, I found and fixed bugs. ◦ → It is useful warning to find bug. • I often find the same warning from validations in app/models/user.rb.
44. instance variable not initialized mizzy/specinfra#685
45. Instance variable not initialized • : def foo @foo ||= something end • : def foo @foo ? @foo : something end ◦ instance variable @foo not initialized
47. Patch
48. Other solutions • Use ||= ◦ @foo ||= something # It is OK • Use defined? ◦ defined?(@foo) ? @foo : something
49. Conclusion
50. Conclusion • We looked warnings examples. ◦ Meanings, how to fix warnings, etc • With using warnings, we can ◦ Find bugs. ◦ Contribute to OSS easier. • Let’s try enabling warnings in your application! Thank you for listening!