Lightning talk at RubyKaigi 2018, Sendai, Japan. Presentation at: https://rubykaigi.org/2018/presentations/lt Moved from: https://niconare.nicovideo.jp/watch/kn3098

1. From
String#undump
to
String#unescape
斎藤ただしただし
Tadashi Saito

2. Do you know
String#undump ?

3. New (unknown)
built-in method in
Ruby 2.5
[bug#12275]

4. What?

5. "Does inverse of
String#dump"

6. end

7. So…

8. Do you know
String#dump ?

9. From the document:
Produces a version of str with
all non-printing characters
replaced by nnn notation and
all special characters escaped.

10. In short:
Escape to
printable ASCII

11. Then,

12. String#undump
(almost) does
unescape from
printable ASCII

13. Escape format
example

14. 1. backslash + one character n t
2. x + 2 hex digits x12
3. u + 4 hex digits u1234
etc etc...

15. because notations used
in #dump is commonly
used among various
languages
#undump is useful

16. I saw first
these in C

17. Ruby Python
Java C# JSON
Nginx…

18. ＿人人人人人人人人人＿
＞ Suddenly Nginx ＜
￣Y^Y^Y^Y^Y^Y^Y^Y￣

19. In fact, Nginx was
my trigger to
implement
String#undump

20. "We need to implement
String#undump to read access log
that Nginx writes"

21. Nginx module
ngx_http_log_module
(access_log, log_format)
spec:

22. Access: /api/{URL-escaped-mbchars}
Automatically!

23. Access: /api/{URL-escaped-mbchars}
↓
Internally: /api/{raw-mbchars}
Automatically!

24. Access: /api/{URL-escaped-mbchars}
↓
Internally: /api/{raw-mbchars}
↓
Log: /api/{xnn-escaped-mbchars}
Automatically!

25. Access log
looks like:

26. /api/xe3x81x82xe3x81x82xe3x81x82xe3x81x82
/api/xe3x81x84xe3x81x84xe3x81x84xe3x81x84
/api/xe3x81x86xe3x81x86xe3x81x86xe3x81x86
/api/xe3x81x88xe3x81x88xe3x81x88xe3x81x88
/api/xe3x81x8axe3x81x8axe3x81x8axe3x81x8a
/api/xe3x81x8bxe3x81x8bxe3x81x8bxe3x81x8b
/api/xe3x81x8dxe3x81x8dxe3x81x8dxe3x81x8d
/api/xe3x81x8fxe3x81x8fxe3x81x8fxe3x81x8f
/api/xe3x81x91xe3x81x91xe3x81x91xe3x81x91
/api/xe3x81x93xe3x81x93xe3x81x93xe3x81x93
:
:
:
:

27. I CAN NOT
READ
for analysis 😢

28. ＿人人人人人人人人人人人人人人＿
＞ Can't change this behavior!! ＜
￣Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y￣
(at that time at least)

29. 💡 Decode with
Ruby!

30. 1. Write it by
myself

31. Easily done,
but...

32. Too common
problem to
implement by
myself?

33. 2. Google it for
gems / codes

34. No gems 😢

35. Stack Overflow:
Loose and partially
incomplete
codes 😢

36. 3. Final means:
Google it in
bugs.ruby-lang.org

37. Ticket found!
[bug#12275]

38. ●
Submitted about
a year ago
●
Specs (including the name
– most difficult part) were
almost fixed! 🙌

39. Matz:
"If someone
implement,
it's OK to add."

40. But no one
implements...

41. 💡 💡 Chance
to commit!

42. I messed up
and worked

43. Shipped as
built-in String
method in
Ruby 2.5! 🎉

44. Thank you for
involved committer /
adviser (especially
@naruse)

45. puts
‘/api/xe3x81x82’.undump

46. #=> RuntimeError
(invalid dumped
string...)

47. ●
undump-ed string must
be wrapped with "…"
like ‘”u1234”’
●
Because String#dump
always wraps with "..."
String#undump Spec

48. Reasonable as spec of
"inverse of #dump",
but...

49. I have a little
regret
(to be honest)

50. ●
A little dull to prepend / append ”
●
Both of the original use-case and
my case don't need this behavior

51. Plan to
improve?

52. 1. Extend existing spec like
str.undump(allow_no_quotes: true)

53. Too long!

54. 2. Introduce new method like
str.just_unescape_backslashed_chars

55. Hard way to
find good
name...

56. So I created a
(personal) gem

57. string_unescape
https://github.com/tadd/string_unescape

58. if self[0] == '"' && self[-1] == '"’
self
else
‘"’ + self + ‘”’
end.undump
Definition

59. puts
'/api/xe3x81x82'.unescape
#=> /api/あ

60. Easy ☺

61. Problems

62. ●
The name may have arguments
– Hard to merge into the core
●
But just works™

63. ●
From business knowledge,
●
Found a potential
and generic problem
●
Implemented as
(core / external) method
Summary of What I did

64. Please make use
●
String#undump (built-in)
&
●
String#unescape
(string_unescape gem)
more!!1