Finding unused code in ruby and ruby on rails projects

unused.md

This is a strategy I use to find unused code in ruby projects. These instructions are for macOS, but you only need access to the tools for this to work.

1. Install unused following the instructions here
2. Install universal-ctags. I use the brew instructions here
3. Generate your tag file from your project root, including your library methods as well. I typically run /usr/local/bin/ctags . $(bundle list --paths) to add all of my library methods for the project. This has some other benefits, like allowing code-jumping in vim

   Bonus: You can set this command up as a git hook to run every time you make changes to your code locally. I have an example of this here

4. Once this command is done, you can look at the tags file in your repository root to make sure it's populated with data correctly (cat tags | wc -l). For context, on an older project I have ~150,000 lines, on a newer project I have ~115,000 lines. In both cases, I have a healthy number of libraries included which are the bulk of the lines
5. Generate your list of unused methods, classes, and constants with unused --ignore <path to gems/library> > out.txt

   In my case, all of my gems are in /Users/jay/.asdf/installs/*; we ignore these paths because I don't care if gem X has an extra method

Inspect the out.txt file to identify methods, classes, and constants you might be able to remove.

Caveats:

1. This won't catch metaprogrammed or dynamically defined values, so be careful