Human Errors

Runtime errors can sometimes turn into dark and unpleasant journeys which lead you to question the nature of reality. Thankfully, Ruby often provides friendly feedback for understanding the cause and remedy for exceptions. Yet, there are situations in which programmers don't receive clear enough context for what really caused an exception and how to address it. We'll look at Ruby's error feedback mechanisms and search for constructive ways in which they can be made more helpful to humans.

This talk was presented at RubyConf 2017.

Transcript

1. Human Errors
2. Humans?
6. Olivier |oh-lee-vee-yay|
7. Olivier |oh-lee-vee-yay|
8. Olivier |oh-lee-vee-yay|
9. Olivier |oh-lee-vee-yay|
10. Olivier |oh-lee-vee-yay|
13. @olivierlacan |figure-it-out|
15. Mistakes
16. purpose” “On
18. (French flag circa 1803)
20. Mistakes are made
21. recovery error
22. recovery error feedback
23. recovery error feedback
24. context error recovery feedback
25. context error recovery feedback
26. Why?
27. What?
28. How?
29. When?
30. Where?
31. Error? What is an
32. error noun the state or condition of being wrong in conduct or judgment: the crash was caused by human error | the money had been paid in error. | ˈerər | a mistake: spelling errors | an error of judgment.
33. the state or condition of being wrong in conduct or judgement
34. Error (technical): a measure of the estimated difference between the observed or calculated value of a quantity and its true value.
35. observed_value != true_value
36. Origin: from Middle English errour, from Latin error (“wandering about”), infinitive of errō (“to wander, to err”). error noun | ˈerər |
37. Wandering
38. Friendliness
39. Hostility
40. STOP
42. End-users
43. USERS 1970 - 2017 Succumbed to yet another Lorum Ipsum placeholder text.
44. Middle-users
46. start
47. start middle
48. start middle end
49. start middle end
50. start middle end
60. ArgumentError
61. def explode(code) puts "#{code} Boom!" end
62. > explode ArgumentError: wrong number of arguments 
 (given 0, expected 1) from (irb):1:in `explode' from (irb):4 from /…/2.4.0/bin/irb:11:in `<main>'
63. > explode ArgumentError: wrong number of arguments 
 (given 0, expected 1) from (irb):1:in `explode' from (irb):4 from /…/2.4.0/bin/irb:11:in `<main>'
64. def explode(code) puts "#{code} Boom!" end
65. > explode("abcd") abcd Boom! => nil
66. def explode(code:) puts "#{code} Boom!" end
67. :
68. > explode ArgumentError: missing keyword: code from (irb):9:in `explode' from (irb):12 from /…/2.4.0/bin/irb:11:in `<main>'
69. > explode("abcd")
70. > explode("abcd") ArgumentError: wrong number of arguments (given 1, expected 0) from (irb):9:in `explode' from (irb):13 from /…/2.4.0/bin/irb:11:in `<main>'
71. def explode(code:) puts "#{code} Boom!" end
73. nobutime! 24d38cc447ee122c07208cf87a7899fe77792b02 c00265bbcc5deb1bcfcd0faa0cf8c4c42968de8e 50702d16ab5862413351520b65da820194dbf8d7 fe3decb2017af2092d4b2181e27e4cd8f6bbf4fa 73e41247b93a74c9b2ec95a374736fdb98fcaac5 a48fac6e226d182d7b1a7d05f47bcd7f1d1e7370 9cabbf849e333d2e09abb323fcd3100c4ef51095 496b4267b2015254edb176f98943d7599b43d22f
77. > explode("abcd") ArgumentError: wrong number of arguments (given 1, expected 0; required keyword: code) from (irb):1:in `explode' from (irb):4 from /…/2.5.0-preview1/bin/irb:11:in `<main>'
79. 2.5.0 Christmas 2017
81. Help Ruby
82. Joy
83. “For me the purpose of life is partly to have joy. Programmers often feel joy when they can concentrate on the creative side of programming, 
 So Ruby is designed to make programmers happy.” Yukihiro “Matz” Matsumoto
84. Rust
86. Elixir
88. Elm
90. Ruby
91. irb(main):015:0> expode NameError: undefined local variable or method `expode' for main:Object Did you mean? explode from (irb):15 from /…/2.4.0/bin/irb:11:in `<main>'
92. Instant Recovery
93. Handling Not
95. Voodoo Contextual
99. foo.call && bar.call NoMethodError: undefined method `call' for nil:NilClass
100. Did it? Who
101. @foo.call && @bar.call ^---- NoMethodError: The method `call` is undefined on receiver nil:NilClass
102. Context First,
103. @foo.call && @bar.call ^---- NoMethodError: The method `call` is undefined on receiver nil:NilClass
104. Feedback Then,
105. undefined method `call' for nil:NilClass
106. The method `call` is undefined on receiver nil:NilClass
107. Clarity Care &
108. Matters How you say it
111. Contextualize Go forth &
113. Elm Street An error on
115. What happened
117. Context: type of error
118. Where it happened
120. How it happened
122. How to recover!
125. $ bin/rspec spec/ --bisect --seed 36929 Bisect started using options: "spec/ --seed 36929" Running suite to find failures... /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/shell_escape.rb:20:in `escape': undefined method `shellescape' for #<Pathname:/Users/olivierlacan/Development/cs/CodeSchool/lib> (NoMethodError) from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:154:in `block in load_path' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:154:in `map' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:154:in `load_path' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:26:in `command_for' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:68:in `block in run_locations' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/server.rb:27:in `capture_run_results' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:67:in `run_locations' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/runner.rb:50:in `original_results' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/example_minimizer.rb:114:in `block in prep' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/example_minimizer.rb:151:in `track_duration' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/example_minimizer.rb:113:in `prep' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/example_minimizer.rb:17:in `find_minimal_repro' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/coordinator.rb:37:in `block (2 levels) in bisect' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/server.rb:18:in `run' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/coordinator.rb:32:in `block in bisect' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:191:in `close_after' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/coordinator.rb:31:in `bisect' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/bisect/coordinator.rb:19:in `bisect_with' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/invocations.rb:32:in `call' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:69:in `run' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:45:in `invoke' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/rspec-core-3.6.0/exe/rspec:4:in `<top (required)>' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/activesupport-5.0.6/lib/active_support/dependencies.rb:287:in `load' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/activesupport-5.0.6/lib/active_support/dependencies.rb:287:in `block in load' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/activesupport-5.0.6/lib/active_support/dependencies.rb:259:in `load_dependency' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/activesupport-5.0.6/lib/active_support/dependencies.rb:287:in `load' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/spring-commands-rspec-1.0.4/lib/spring/commands/rspec.rb:18:in `call' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/nakayoshi_fork-0.0.3/lib/nakayoshi_fork.rb:24:in `fork' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/gems/2.3.0/gems/nakayoshi_fork-0.0.3/lib/nakayoshi_fork.rb:24:in `fork' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /Users/olivierlacan/.rbenv/versions/2.3.4/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require' from -e:1:in `<main>'
126. undefined method `shellescape' for #<Pathname:/.../lib> (NoMethodError)
127. What happened
128. rspec-core-3.6.0/lib/rspec/core/bisect/ runner.rb:154:in `block in load_path'
129. Where it happened
130. Where it happened ?
131. How it happened
132. How it happened
133. How to recover!
134. How to recover!
136. Unclear & too late
137. ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
138. What happened
139. What happened
140. Where it happened
141. Where it happened
142. How it happened
143. How it happened
144. How to recover!
145. How to recover!
147. What’s missing?
148. A way foward
149. context error recovery feedback
150. Resolution Hints
151. “A library or application not having a functional need to rescue a possible error doesn't grant us license to ignore how confusing that error may be for the person who ultimately sees it.” Justin Searls
152. Libraries
153. Maintainers & users
154. Farm-to-table Exceptions
155. Languages
156. Implementors & users
157. Turn-by-turn Contextualization
158. Work to do
159. error.c
160. * The built-in subclasses of Exception are: * * * NoMemoryError * * ScriptError * * LoadError * * NotImplementedError * * SyntaxError * * SecurityError * * SignalException * * Interrupt * * StandardError -- default for +rescue+ * * ArgumentError * * UncaughtThrowError * * EncodingError * * FiberError * * IOError * * EOFError * * IndexError
162. ArgumentError
164. ERROR EXCEPTION
165. ERROR FAILURE
166. ERROR FAILURE EXCEPTION
167. ERROR FAILURE EXCEPTION
168. Let's make it a rule to take better care of our exceptions.
170. Merci
171. @olivierlacan