This document discusses code smells and tools for analyzing Ruby code quality. It notes that most code changes involve modifying existing code. It then describes several static code analysis tools like Reek, Flog, and Roodi that inspect code without running it, as well as runtime tools like RSpec and SimpleCov that execute code. Finally, it emphasizes the importance of both static analysis and testing, and recommends trying the RubyMine IDE for refactoring code.

1. Fighting Code Smells
ruby code analysis tools
Dennis Ushakov

2. Pareto Principle
• 20%
Write new code
• 80%
Modify existing code

3. Does This Smell?
a = something.valid?
if (a.to_s == "true")
# code here
end

4. Does This Smell?
def has_currency_rate?
val = false
if currency.id == company.currency.id or rate.blank?
else
val = true
end
val
end

5. Does This Smell?
class FinancialEventObserver < ActiveRecord::Observer
observe Payment, Invoice
def before_save(model)
event = nil
if model.class == Payment
if model.new_record?
event = FinancialEvent.new(:event => FinancialEvent::Event::PAYMENT_INVOICE,
:arguments => {:client_name => model.invoice.client.short_name, :invoice_number =>
model.invoice.invoice_number},
:company_id=>model.invoice.client.company.id)
end
elsif model.class == Invoice
i = Invoice.find_by_id model.id
if model.new_record? or i.status != model.status
if model.status == Invoice::Status::ESTIMATE
event = FinancialEvent.new(:event => FinancialEvent::Event::ESTIMATE_SEND,
:arguments => {:client_name => model.client.short_name, :invoice_number => model.invoice_number},
:company_id=>model.client.company.id)
elsif model.status == Invoice::Status::APPROVED
event = FinancialEvent.new(:event => FinancialEvent::Event::ESTIMATE_APPROVED,
:arguments => {:client_name => model.client.short_name, :invoice_number => model.invoice_number},
:company_id=>model.client.company.id)
elsif model.status == Invoice::Status::REJECTED
event = FinancialEvent.new(:event => FinancialEvent::Event::ESTIMATE_REJECTED,
:arguments => {:client_name => model.client.short_name, :invoice_number => model.invoice_number},
:company_id=>model.client.company.id)
elsif model.status == Invoice::Status::SEND
event = FinancialEvent.new(:event => FinancialEvent::Event::INVOICE_SEND,
:arguments => {:client_name => model.client.short_name, :invoice_number => model.invoice_number},
:company_id=>model.client.company.id)
end
elsif !model.new_record? and i.state != model.state
if model.state == Invoice::State::DELETED
event = FinancialEvent.new(:event => FinancialEvent::Event::INVOICE_DELETED,
:arguments => {:invoice_number => model.invoice_number},
:company_id=>model.client.company.id)
end
end
end
event.eventable = model.requester unless event.blank?
event.save unless event.blank?

6. Code That Smells
• Runtime errors
• Runtime warnings
• Dead code
• Copy/paste
• Complex method bodies
• Code style violations
• Framework pattern violations

7. Code Quality Tools
Static Runtime
flay roodi rspec
metrics_fu rcov
dust simplecov
heckle reek autotest
pelusa cucumber
flog

8. Static Tools
• Inspect your code without launching it
• 100% side effects free
• Challenging to implement
• Rails DSL magic kills ‘em

9. Reek
• Class, module, method, identifier names
• Using is_a?, kind_of? instead of duck typing
• Code duplicates
• Large classes and methods
• Nested iterators

10. Flog
• Uses ABC metrics system
• Assignment
• Branches
• Conditions
• |ABC| = √(A²+B²+C²)
• Consider revising most
painful methods

11. Flay
• Analyzes code duplicates
• Ignores identifier/
constants names
• Consider refactoring
code that’s reported

12. Roodi
• Assignments in conditions
• Case blocks without else
• Large classes, modules and methods
• Naming conventions
• Cyclomatic complexity

13. metrics_fu/metrical
Provides aggregate results for
• Flay
• Flog
• Reek
• Roodi

14. Runtime Tools
• Inspect your code by launching it
• 100% follow the way Ruby works
• Cope well with DSL magic
• May have side effects
• Works until the very first failure

15. Runtime Tools
• Code testing
• Test::Unit/MiniTest
• RSpec/Cucumber
• Autotest/CI
• Code coverage
• RCov/SimpleCov
• Heckle

16. Heckle
• Changes code
• if → unless
• Calls are changed
• Numbers are changed
• Runs tests
• At least one test should
fail after change

17. RubyMine
• Static analysis
• On-the-fly inspections with quickfixes
• Understands Rails DSLs
• Code duplication
• Dynamic analysis tools integration
• Graphical representation
• Autotest simulation
• Stacktrace navigation

18. Refactorings
• Rename
• Extract
• Method
• Class/Module
• Variable/Parameter

19. Morale
• Use static analysis
tools
• Don’t forget to test
• Try RubyMine
http://jetbrains.com/
ruby

20. dennis.ushakov@jetbrains.com
en_Dal
denofevil