Tool for finding unused constructs in Ruby code?

Question

Can Anyone point Me to a tool to detect unused code, objects, methods, parameters, etc., in Ruby code?

I saw nitpick but it does not seem to give me the coverage I want. I also checked laser and reek but their respective gems seem to have issues which prevent them from running.

I thought at one point the Ruby binary had a mode which would detect unused constructs but I do not seem to be able to find it.

mbj · Accepted Answer · 2012-12-10 14:15:48Z

1

You can also use a mutation tester that mutates your code. In case the mutation tester can delete a construct without your tests noticing. You found an unused construct.

I know two mutation testers for ruby:

Disclaimer, I'm the author of mutant.

Depending on your setup, your ruby version, spec layout, test framework heckle and or mutant can do the job for you.

Here you can see mutant in action: http://ascii.io/a/1707

answered Dec 10, 2012 at 14:15

mbj

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Favourite Onwuemene · Accepted Answer · 2012-09-27 18:01:51Z

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JetBrains RubyMine http://www.jetbrains.com/ruby/quickstart/index.html

answered Sep 27, 2012 at 18:01

Favourite Onwuemene

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xuinkrbin. Over a year ago

Unfortunately, RubyMine seems to only catch unused local variables.

Matt · Accepted Answer · 2012-09-27 18:01:07Z

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It might help if we had a little more context in how you want to "detect unused code" - is this code coverage of your tests you're looking into? Otherwise, how would you know from run to run whether you hit all the use cases? Or are you looking for a statistical "heat map" of coverage over time for e.g. performance reasons?

In any case, for code coverage while testing I use SimpleCov - it uses Ruby 1.9's built-in Coverage library with some nice sugar on top.

answered Sep 27, 2012 at 18:01

Matt

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xuinkrbin. Over a year ago

The scripts in question are self-contained programs, as a general rule. The methods within a given script would all be invoked within that script with the exception of one used to interface with "the outside world", so to speak. So, knowing if a script "hit all the use cases" is pretty simple: either the method is invoked or its not.

iconoclast · Accepted Answer · 2023-09-18 18:55:34Z

You can use a static analysis tool like Debride to find methods that appear to be unused. It is not guaranteed to be correct, since you can dynamically construct the methods you want to call, and as a static analysis tool it does not actually run your code to see what is used and what is not used.

You can also use a tool like Coverband to detect (in production) which methods get called. In this case a method might not be called because it belongs to a feature that no one cares about, even though there is a code path through which it could hypothetically be called.

I recommend using both. One takes a more rationalistic approach and the other a more empirical approach, and between the two the chances of wrongly identifying unused code seems extremely low.

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