Extremely Defensive Coding

Transcript

1. Extremely Defensive Coding
2. a!/samphippen
3. I want to start with a story
4. “When is it OK to override the methods on object?”
5. I umm’d and ahh’d for a bit
6. I gave a half explanation and then asked them if they understood
7. I eventually came to an answer to do with consistency
8. Do it when it makes your object more consistent with Ruby, not less
9. e.g. an == on a data object
10. What makes a gem good?
11. Internals?
12. Internals?
13. Interface?
14. Interface? ✅
15. More convenient than if I did it myself
16. And it stays convenient
17. And it can be used by everyone on a team
18. And it works with a wide range of Ruby codebases
19. I don’t want much do I?
20. RSpec
21. RSpec Definitely always convenient
22. RSpec Definitely always convenient
23. User story
24. As an RSpec user
25. When I stub an object
26. I want the original method to be on that object after the example
27. So that my objects aren’t broken by my test suite
28. As an RSpec user
29. When I stub an object
30. I want the original method to be on that object after the example
31. So that my objects aren’t broken by my test suite
32. How does that work?
33. allow(cat).to receive(:meow)
34. Takes the meow method off cat
35. Saves it
36. Executes test
37. Puts the method back on the original object
38. How do you save a method?
40. Method object
41. Put it somewhere else
42. Put it back at end of test
43. The end
44. The end
45. Defensive coding
46. RSpec::Support .method_handle_for
47. Simply invoking the method method is not good enough
48. Some scenes may have been altered/accelerated for your viewing pleasure
49. Let’s have some questions !!/samphippen sam@funandplausible.com
50. Users Lie
51. def method ‘get’ end
52. Users can redefine anything at any time in Ruby
53. Let’s have some questions !!/samphippen sam@funandplausible.com
54. Let’s have some questions !!/samphippen sam@funandplausible.com
55. Instance method object Method without a target object
56. Comes from a class/module not an instance
57. Grab the Kernel implementation of #method
58. Let’s have some questions !!/samphippen sam@funandplausible.com
59. Let’s have some questions !!/samphippen sam@funandplausible.com
60. Users can and will redefine core methods at any time
61. Instead we use Kernel’s implementation
62. Nobody screws with Kernel
63. Ruby interpreters lie
64. Some objects do not have Kernel in their inheritance chain
66. Let’s have some questions !!/samphippen sam@funandplausible.com
67. Let’s have some questions !!/samphippen sam@funandplausible.com
68. Let’s have some questions !!/samphippen sam@funandplausible.com
69. Rebinding module methods
70. c
71. c
72. RSpec does not support Rubinius
74. We tried, we really really tried
75. So anyway, dealing with module methods
76. Let’s have some questions !!/samphippen sam@funandplausible.com
77. Let’s have some questions !!/samphippen sam@funandplausible.com
78. Let’s have some questions !!/samphippen sam@funandplausible.com
79. Let’s have some questions !!/samphippen sam@funandplausible.com
80. Let’s have some questions !!/samphippen sam@funandplausible.com
81. Let’s have some questions !!/samphippen sam@funandplausible.com
82. Let’s have some questions !!/samphippen sam@funandplausible.com
83. Let’s have some questions !!/samphippen sam@funandplausible.com
84. Let’s have some questions !!/samphippen sam@funandplausible.com
85. Let’s have some questions !!/samphippen sam@funandplausible.com
86. Ruby interpreters behave differently.
87. Let’s have some questions !!/samphippen sam@funandplausible.com
88. Sometimes users don’t lie
93. `method': undefined method `foo' for class `Foo' (NameError)
94. This is a catch 22
95. Solution: trust but verify
99. Let’s put it all together
101. Wrapping up
102. This is why I love RSpec
103. Please file bugs
104. Your gem should be defensive
105. Users lie Redefinitions come from anywhere, expect them
106. Ruby interpreters lie Your code will run on non-MRI, old MRI, etc
107. Sometimes users don’t lie Users are weird, trust but verify
108. What makes a gem good?
109. Internals?
110. That explanation made no sense
111. Internals?
112. Interface?
113. allow(cat).to receive(:meow)
114. You get the complexity of RSpec working with any object for free
115. You probably didn’t even know it was there until I just told you
116. Interface? ✅
117. Gems
118. Gems are like super objects
119. Done badly they cause an even more extreme mess
120. Done correctly they hide huge complexity behind well defined barriers
121. Defending against users helps your gem be convenient
122. Write defensively, and your users will never know what’s inside the box
123. Remember the story?
124. This talk is born out of Ruby’s power
125. We need our code to defend today, against the mistakes of our tomorrow
127. Let’s have some questions a!/samphippen sam@funandplausible.com