Excellent is a static analysis gem that finds the nasty lines in your code. It implements a comprehensive set of checks for possibly buggy parts of your app that would otherwise make it into your repo and eventually to the production server.

1. Excellent

2. Me
Marco Otte-Witte
• Freelancer since 2007
• Web Development since ~1998
• PHP => (Java) => .NET => Ruby (on Rails)
• http://simplabs.com
• http://xing.com/profile/Marco_OtteWitte
• http://github.com/marcoow

3. Excellent
• static code analysis for Ruby
• like roodi, flog, reek etc. but more
• static code analysis for Rails
• (it‘s still beta despite the 1.5.4 - be kind)

4. Static Analysis
• it‘s not about finding errors
• it‘s no red/ green, no fail/ pass
• it‘s about getting hints on possible problems
• don‘t try to code for zero warnings!

5. Complexity Measures
global.checkEmail = function(e) {
function checkChars(s, i, l) {
while (i < l && "_-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".indexOf(s.charAt(i)) != -1)
{
i = ++i;
} // end while
return (i);
}
function checkFirstLevelDomainChars(s, i, l)
{
while (i < l && "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".indexOf(s.charAt(j)) != -1)
{
i = ++i;
} // end while
return (i == l);
} // End of the function
var _loc1;
var j;
var _loc2 = e.length;
var _loc4 = false;
_loc1 = checkChars(e, 0, _loc2);
if (checkChars(e, 0, _loc2) == 0)
{
return (-1);
} // end if
j = _loc1;
while (_loc1 < _loc2 && e.charAt(_loc1) == ".")
{
...

6. Complexity Measures
• Cyclomatic Complexity
• ABC metric
• Flog
• also: method line count, even class name check
• etc.

7. Rails specific checks
• no restriction on (sometimes helpful, sometime not
so helpful) complexity measures etc.
• Rails checks can be red/ green
• no magic, finds stuff you forgot/ didn‘t know about
• AttrAccessibleCheck: specify attr_accessible!
• ValidationsCheck: validate!
• InstanceVarInPartialCheck: don‘t use instance vars
in partials!

8. Rails specific checks
1 class ShoppingBasket < ActiveRecord::Base
2
3 def initialize(items = [])
4 self.items = items
5 end
6
7 end

9. Rails specific checks
1 class ShoppingBasket < ActiveRecord::Base
2
3 def initialize(items = [])
4 self.items = items
5 end
6
7 end
$ excellent shopping_basket.rb
Excellent result:
test.rb
* Line 1: ShoppingBasket does not validate any attributes.
* Line 1: ShoppingBasket defines initialize method.
* Line 1: ShoppingBasket does not specify attr_accessible.
Found 3 warnings.

10. How does it work?
• ruby_parser
• sexp_processor
• Stack of context infos
• simple checks on these contexts

11. Run it via rake
1 require 'simplabs/excellent/rake'
2
3 desc 'Analyse the Excellent source with itself.'
4 Simplabs::Excellent::Rake::ExcellentTask.new(:excellent) do |t|
5 t.html = 'doc/excellent.html'
6 t.paths = ['lib']
7 end

12. with HTML reports

13. Get it
• http://simplabs.github.com/excellent/

14. Get it
• http://simplabs.github.com/excellent/
$ sudo gem install gemcutter
$ sudo gem tumble
$ sudo gem install excellent

15. Resources
• http://simplabs.github.com/excellent/
• http://wiki.github.com/simplabs/excellent
• http://static.simplabs.com/rails3-0-unstable.html
• http://parsetree.rubyforge.org/