Talk given at Euruko 2010: the talk describes how to quickly evaluate the quality of a Rails codebase. Ruby metrics are explained in detail.

1. How to rate a
Rails application
Elise Huard @elise_huard
http://jabberwocky.eu
Sunday 30 May 2010

2. Acquisition
Sunday 30 May 2010

3. Maintenance
Sunday 30 May 2010

4. Where to Start ?
Sunday 30 May 2010

5. Try the app
Björn Söderqvist on Flickr
Sunday 30 May 2010

6. Rails version
Sunday 30 May 2010

7. plugins and
gems
Photo Lex on Flickr
Sunday 30 May 2010

8. Sunday 30 May 2010

9. Run Tests
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10. Lots of code
Sunday 30 May 2010

11. config/routes.rb
match ‘/’, :to => ‘root#index’
match ‘root’, :to => ‘root#index’
namespace :admin do
resources :grids do
resources :nodes
resources :edges do
collection do
post :all
post :update_all
end
end
resources :walkers
end
end
resources :nodes, :only => [:show,:new,:create,:destroy] do
put :directions, :on => :collection
end
resources :walkers, :only => [:show,:new,:create,:destroy] do
get :select, :on => :collection
end
resources :itineraries, :only => [:show]
Sunday 30 May 2010 map.four_oh_four '*path' , :controller => 'four_oh_fours'

12. models
railroad -M | dot Tpng > models.png
rubymine ctrl-alt-D
Sunday 30 May 2010

13. names
“There are only two hard things in
Computer Science: cache
invalidation and naming things”
Phil Karlton
Sunday 30 May 2010

14. Metrics:
Know thine Tools
docman on flickr
Sunday 30 May 2010

15. LOC
rake stats
+----------------------+-------+-------+---------+---------+-----+-------+
| Name | Lines | LOC | Classes | Methods | M/C | LOC/M |
+----------------------+-------+-------+---------+---------+-----+-------+
| Controllers | 2702 | 2150 | 36 | 158 | 4 | 11 |
| Helpers | 358 | 303 | 0 | 22 | 0 | 11 |
| Models | 1358 | 1104 | 30 | 117 | 3 | 7 |
| Libraries | 2286 | 1655 | 38 | 152 | 4 | 8 |
| Integration tests | 0 | 0 | 0 | 0 | 0 | 0 |
| Functional tests | 1687 | 1322 | 31 | 195 | 6 | 4 |
| Unit tests | 1356 | 1079 | 27 | 158 | 5 | 4 |
+----------------------+-------+-------+---------+---------+-----+-------+
| Total | 9747 | 7613 | 162 | 802 | 4 | 7 |
+----------------------+-------+-------+---------+---------+-----+-------+
Code LOC: 5212 Test LOC: 2401 Code to Test Ratio: 1:0.5
Sunday 30 May 2010

16. RubyParser and
Parsetree
Ryan Davis and Eric Hodel
(‘Ruby Sadists’)
Sunday 30 May 2010

17. RubyParser and
Parsetree
Abstract syntax tree
RubyParser.new.parse(File.read(‘metrics.rb’),‘metric.rb’)
class Metrics s(:class,:Metrics, nil,
def probe s(:scope,
s(:defn,:probe,
puts "good" s(:args),
end s(:scope,
end s(:block,
s(:call, nil, :puts,
s(:arglist,
s(:str, "good"))))))))
Symbolic Expression (Sexp)
Sunday 30 May 2010

18. RubyParser and
Parsetree
Abstract syntax tree
RubyParser.new.parse(File.read(‘metrics.rb’),‘metric.rb’)
class Metrics s(:class,:Metrics, nil,
def probe s(:scope,
s(:defn,:probe,
puts "good" s(:args),
end s(:scope,
end s(:block,
s(:call, nil, :puts,
s(:arglist,
s(:str, "good"))))))))
Symbolic Expression (Sexp)
Ruby2Ruby
Sunday 30 May 2010

19. RubyParser
pure ruby
Parsetree
ruby and inline c
< 1.9
Sunday 30 May 2010

20. rake stats
size
Flog Flay
code complexity code similarities
Roodi
R_B_P
Saikuro Reek
cyclomatic antipatterns Rails
complexity
Heckle Rcov
test coverage
Sunday 30 May 2010

21. flog
‘the pain your code
is in’
Sunday 30 May 2010

22. FLOG
flog lib/flog.rb
647.8: flog total
13.8: flog/method average
87.5: Flog#output_details
58.8: Flog#process_iter
54.2: Flog#flog
48.8: Flog#parse_options
34.1: Flog#none
23.2: Flog#output_method_details
22.1: Flog#score_method
16.0: Flog#process_block_pass
15.6: Flog#report
15.2: Flog#expand_dirs_to_files
15.0: Flog#klass_name
Sunday 30 May 2010

23. FLOG
Assignment Branch Condition (ABC)
def score_method(tally)
a, b, c = 0, 0, 0
tally.each do |cat, score|
case cat
when :assignment then a += score
when :branch then b += score
else c += score
end
end
Math.sqrt(a*a + b*b + c*c)
end
Sunday 30 May 2010

24. FLOG
Weighing the AST with factors
def process_if(exp)
add_to_score :branch
process exp.shift # cond
penalize_by 0.1 do
process exp.shift # true
process exp.shift # false
end
s()
end
Sunday 30 May 2010

25. FLOG
Methods
Very good: < 20
All Right: < 50
Sunday 30 May 2010

26. FLAY
code similarities
Sunday 30 May 2010

27. FLAY
flay *.rb
Total score (lower is better) = 621
1) IDENTICAL code found in :defn (mass*2 = 188)
channel.rb:48
clip.rb:80
2) Similar code found in :defn (mass = 93)
channel.rb:150
clip.rb:110
clip.rb:116
3) Similar code found in :defs (mass = 58)
contact.rb:32
contact.rb:37
Sunday 30 May 2010

28. FLAY
RubyParser
def mass
@mass ||= self.structure.flatten.size
end
Hash of structure of nodes with mass >
threshold
self.hashes[node.structural_hash] << node
analyze:
if same hash = similar
if same node = identical
Sunday 30 May 2010

29. Saikuro
cyclomatic
complexity
Sunday 30 May 2010

30. Saikuro
Sunday 30 May 2010

31. Saikuro
ruby-lex
every keyword is interpreted into
‘state’
state used to calculate
if, unless, while, until, for, elsif, when, rescue
(blocks)
Recursively
Sunday 30 May 2010

32. Saikuro
Good:
methods < 5
Sunday 30 May 2010

33. Roodi
‘Ruby Object Oriented Design Inferometer’
nutmeg66 on flickr
Sunday 30 May 2010

34. Roodi
app/controllers/itineraries_controller.rb:4 - Method name "show" cyclomatic complexity
is 14. It should be 8 or less.
app/models/itinerary.rb:41 - Block cyclomatic complexity is 6. It should be 4 or less.
app/controllers/itineraries_controller.rb:4 - Method "show" has 30 lines. It should
have 20 or less.
app/helpers/application_helper.rb:27 - Method "clippy" has 26 lines. It should have 20
or less.
Sunday 30 May 2010

35. Roodi
RubyParser
visitor pattern
visitor: checker (Configuration)
visitable: parsed nodes
= extensible
Sunday 30 May 2010

36. Reek
Sunday 30 May 2010

37. Reek
more OO-specific checks
Control Couple
Data Clump
Feature Envy
Large Class
Long Method
Long Parameter List
Simulated Polymorphism
Uncommunicative Name
Sunday 30 May 2010

38. Reek
UserSessionsController has no descriptive comment (Irresponsible Module)
UserSessionsController#destroy calls current_user_session twice
(Duplication)
app/controllers/users_controller.rb -- 5 warnings:
UsersController has no descriptive comment (Irresponsible Module)
UsersController tests @aid_app at least 4 times (Simulated Polymorphism)
UsersController#create calls params 3 times (Duplication)
UsersController#create calls params[:user] 3 times (Duplication)
...
Sunday 30 May 2010

39. Reek
RubyParser
extends parsed nodes
traverses nodes
returns code after Ruby2Ruby
Sunday 30 May 2010

40. rails_best_practices
kamoda on Flickr
Sunday 30 May 2010

41. rails_best_practices
./app/controllers/ws/vmg/aid_user_accounts_controller.rb:160 - move model logic into model
(@aid_user_account called_count > 4)
./app/controllers/ws/vmg/ipt_controller.rb:102 - move model logic into model (xml
called_count > 4)
./app/controllers/ws/vmg/ipt_controller.rb:102 - move model logic into model (pf
called_count > 4)
./config/routes.rb:3 - overuse route customizations (customize_count > 3)
./config/routes.rb:35 - overuse route customizations (customize_count > 3)
./app/models/vmg/scenario.rb:41 - keep finders on their own model
Sunday 30 May 2010

42. rails_best_practices
Visitor pattern
visitor : checking_visitor
visitable: visitable sexp
Sunday 30 May 2010

43. Churn
Sunday 30 May 2010

44. Churn
+-------------------------------------------------+---------------+
| file_path | times_changed |
+-------------------------------------------------+---------------+
| db/schema.rb | 26 |
| config/routes.rb | 24 |
| app/controllers/application_controller.rb | 22 |
| app/controllers/add_apps_controller.rb | 22 |
| config/environment.rb | 20 |
| app/views/layouts/application.html.erb | 20 |
| app/models/ability.rb | 18 |
...
Sunday 30 May 2010

45. Churn
Not only classes but also methods
(RubyParser)
Version control: git, Hg, svn
Locates changes in source using logs
(as in git log)
Sunday 30 May 2010

46. Churn
common sense ...
mostly useful in maintenance phase
Sunday 30 May 2010

47. Rcov
Sunday 30 May 2010

48. Rcov
Total coverage: comments included
Sunday 30 May 2010

49. Rcov
Executes test
keeps track of the executed lines
Using C extension when possible
to hook into MRI
(experimental for 1.9)
Sunday 30 May 2010

50. Rcov
good: 100% coverage
Sunday 30 May 2010

51. Heckle
Sunday 30 May 2010

52. Heckle
ParseTree + Ruby2Ruby
mutate
time-consuming: combinatorials
more for small programs (gems,
scripts)
doesn’t work for ruby 1.9
(ParseTree)
Sunday 30 May 2010

53. Heckle
Initial tests pass. Let's rumble.
**********************************************************************
*** AidApp#property_names loaded with 4 possible mutations
**********************************************************************
4 mutations remaining...
Replacing AidApp#property_names with:
--- original
+++ mutation
def property_names
- (meta_policy and meta_policy.property_names_for(:aid_app))
+ (nil and meta_policy.property_names_for(:aid_app))
end
Sunday 30 May 2010

54. rake stats
size
Flog Flay
code complexity code similarities
Roodi
Saikuro Reek
cyclomatic antipatterns RAILS_BEST
complexity _PRACTICES
Heckle Rcov
test coverage
Sunday 30 May 2010

55. metric_fu
Sunday 30 May 2010

56. check out the good stuff
OrbitalJoe on flickr
Sunday 30 May 2010

57. what these metrics don’t
tell you
Bugs
Sunday 30 May 2010

58. what these metrics don’t
tell you
code performance
Ruby Profiling
Sunday 30 May 2010

59. Reads like a book
Sunday 30 May 2010

60. http://railroad.rubyforge.org/
http://www.igvita.com/2008/12/11/ruby-ast-for-fun-and-profit/
http://ruby.sadi.st/Ruby_Sadist.html
http://goruco2008.confreaks.com/04_davis.html
http://cwd.dhemery.com/2009/11/wmaat/
http://c2.com/cgi/wiki?AbcMetric
http://hissa.nist.gov/HHRFdata/Artifacts/ITLdoc/235/title.htm
http://blog.rubybestpractices.com/posts/judofyr/sexp-for-
rubyists.html
Elise Huard @elise_huard
elise@elisehuard.be
http://jabberwocky.eu
http://github.com/elisehuard
Sunday 30 May 2010