Find Unused Code in a Rails App

Find unused code in a Rails app

Under normal circumstances the approach would be to use your test data for code coverage, but as you say you have parts of your code that are tested but are not used on the production app, you could do something slightly different.

Just for clarity first: Don't trust automatic tools. They will only show you results for things you actively test, nothing more.

With the disclaimer behind us, I propose you use a code coverage tool (like rcov or simplecov for Ruby 1.9) on your production app and measure the code paths that are actually used by your users. While these tools were originally designed for measuring test coverage, you could also use them for production coverage

Under the assumption that during the test time-frame all relevant code paths are visited, you can remove the rest. Unfortunately, this assumption will most probably not fully hold. So you will still have to apply your knowledge of the app and its inner workings when removing parts. This is even more important when removing declarative parts (like model references) as those are often not directly run but only used for configuring other parts of the system.

Another approach which could be combined with the above is to try to refactor your app into distinguished features that you can turn on and off. Then you can turn features that are suspected to be unused off and check if nobody complains :)

And as a final note: you won't find a magic tool to do your full analysis. That's because no tool can know whether a certain piece of code is used by actual users or not. The only thing that tools can do is create (more or less) static reachability graphs, telling you if your code is somehow called from a certain point. With a dynamic language like Ruby even this is rather hard to achieve, as static analysis doesn't bring much insight in the face of meta-programming or dynamic calls that are heavily used in a rails context. So some tools actually run your code or try to get insight from test coverage. But there is definitely no magic spell.

So given the high internal (mostly hidden) complexity of a rails application, you will not get around to do most of the analysis by hand. The best advice would probably be to try to modularize your app and turn off certain modules to test f they are not used. This can be supported by proper integration tests.

How to find all unused code in Ruby on Rails

You can look at this answer, and perhaps some of the other answers listed: https://stackoverflow.com/a/9788511/485864

I would probably end up logging the methods that you have, and run your code through the paths and anything not listed in the log, may be examined to see if it is indeed not used.

Find Dead Rails Code

This is a tricky problem without an easy, always-right answer. Some places to start include:

1. Sweep unused code into the dustbin with rcov
2. Performance Testing Ruby on Rails Applications
3. Find unused code in a Rails app

The biggest issue is that unused code and unreachable code aren't the same things. Just because code isn't exercised routinely in production doesn't really mean it's dead code that should be removed. It may be there for a reason---just not one that comes up often.

finding unused javascript in rails

Are you referring to rjs (Rails-generated) or standard js files? If it's the latter then you can use jslint. For the first type you should have some integration tests that fail when you remove the RJS that is being used, if not you'll have to add those tests first.

For more see: Is there a tool to remove unused methods in javascript?

How to find unused CSS from rails? deadweight not working

As mentioned in the comment, there is a good reason why you shouldn't be looking for such a tool - javascript. Even though, given selector might not exist in your templates, you might have some javascript which will add a class to one DOM element, an attribute to another and you might have another rare case which will add another class to another element or move it complete somewhere else inside the DOM.

To actually find whether your CSS selector exists or not, your tool would need to render all your templates and keep executing random js events until given selector shows off - and it will need to be able to tell whether it is ever gona find it. This is a halting problem, proved to be computable impossible to solve.

That being said, you can always use tools like the one listed on other answers - they might give you a list of suspicious selectors, however you will need to spend significant amount of time with every single one of them to find if there is a single case in your application when it can actually be used.

Word of warning: DustMe crawl the website through all the links on your page to get a better view of whole website - you don't use link_to ..., method: <post|delete|put>, do you?

how to know unused routes in rails

I found a gem that seems to do this: amatsuda/traceroute. I haven't tried it myself, but judging from the description it does the right thing - checks for resourceful routes that are defined, but a correcponding action is not created.

But I'd admit one should be very careful with analysing links that are visited and that are not. If no one ever visits this link does not mean it is not going to be visited in the future.

How to find unused gems and cleanup gemfile

I think it is impossible. When your APP starts it loads gems from Gemfile.lock but it does not know if they (gems) are needed in your code or not. The APP inform you by raising an exception When something calls a class or method that is undefined if some needed gem is missed (if you remove it from Gemfile), but this can happen at any moment (not during starting your APP).

So if you are looking the way to clean up your gem list I think the best way to do it manually (I know it is not easy way). Analyse each gem to find out what functionality it provides and decide (or find in your code) if it is needed or not. Additionally tests (if you have them) should help you a lot.

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