Ruby Science

Tools to Find Smells

Some smells are easy to find while you’re reading code and change sets, but other smells slip through the cracks without extra help.

Duplication is one of the hardest problems to find by hand. If you’re using diffs during code reviews, it will be invisible when you copy and paste existing methods. The original method will be unchanged and won’t show up in the diff, so unless the reviewer knows and remembers that the original existed, they won’t notice that the copied method isn’t just a new addition. Every duplicated piece of code is a bug waiting to happen.

Churn is similarly invisible, in that each change will look fine, and only the file’s full history will reveal the smell.

Various tools are available which can aid you in your search for code smells.

Our favorite is Code Climate, which is a hosted tool and will scan your code for issues every time you push to Git. Code Climate attempts to locate hot spots for refactoring and assigns each class a simple A through F grade. It identifies complexity, duplication, churn and code smells.

If you’re unable to use a hosted service, there are gems you can use locally, such as metric_fu, churn, flog, flay, and reek. These gems can identify churn, complexity, duplication and smells.

Getting obsessed with the counts and scores from these tools will distract from the actual issues in your code, but it’s worthwhile to run them continually and watch out for potential warning signs.

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