# Unused [![Build Status](https://travis-ci.org/joshuaclayton/unused.svg?branch=master)](https://travis-ci.org/joshuaclayton/unused) A command line tool to identify unused code. # NOTICE: As of May 27, 2020, this version of Unused has been deprecated Unused has been rewritten and now lives at https://github.com/unused-code/unused Issues, updates, and all future work will occur there. ![Image of Unused Output](http://i.giphy.com/3o7qDT1I4OfQxnJTvW.gif) ## "What kinds of projects can I used it on?" Anything. Yes, literally anything. It's probably best if you have a file generated from `ctags` it can read from (it looks in `.git`, `tmp`, and the root directory for a `tags` file), but if you have another way to pipe a bunch of methods/functions/classes/modules/whatever in, that works too. Right now, there are some special cases built in for Rails and Phoenix apps (specifically, assumptions about what's fine to only have one reference to, e.g. Controllers in Rails and Views in Phoenix), but it'll work on Rubygems, Elixir packages, or anything else. That said, **be confident the code you're removing won't break your program**. Especially with projects built in Ruby, Elixir, or JavaScript, there are ways to dynamically trigger or define behavior that may be surprising. A test suite can help here, but still cannot determine every possible execution path. ## Installing and Updating ### Homebrew (Recommended) You can install [my formulae] via [Homebrew] with `brew tap`: ```sh brew tap joshuaclayton/formulae ``` Next, run: ```sh brew install unused ``` [my formulae]: https://github.com/joshuaclayton/homebrew-formulae [Homebrew]: http://brew.sh/ This will install `unused` and its corresponding dependencies. To update, run: ```sh brew update brew upgrade unused ``` Alternatively, you can install with [Stack] or by hand. Because it needs to compile, installation times may vary, but it's often several minutes. ### Stack If you already have [Stack] installed, ensure you have the latest list of packages: ```sh stack update ``` Verify Stack is using at least `lts-6.0` when installing by checking the global project settings in `~/.stack/global-project/stack.yaml`. Once that is complete, run: ```sh stack install unused ``` This will install unused in the appropriate directory for Stack; you'll want to ensure your `$PATH` reflects this. ### Installing by hand This project is written in [Haskell] and uses [Stack]. Once you have these tools installed and the project cloned locally: ```sh stack setup stack install ``` This will generate a binary in `$HOME/.local/bin`; ensure this directory is in your `$PATH`. [Haskell]: https://www.haskell.org [Stack]: http://www.haskellstack.org ### Install via Docker Once [Docker is installed], create a binary within your `$PATH` to run the image: ```bash #!/usr/bin/env bash docker run --rm -it -v $(pwd):/code joshuaclayton/unused unused $@ ``` Note that, because Unused will be running inside of a virtual machine, it will take longer to generate output than were you to install via previously-mentioned methods. [Docker is installed]: https://docs.docker.com/engine/installation ## Using Unused `unused` attempts to read from common tags file locations (`.git/tags`, `tags`, and `tmp/tags`). In an application where the tags file exists, run: ```sh unused ``` If you don't have a tags file, you can generate one by running: ```sh git ls-files | xargs ctags ``` If you want to specify a custom tags file, or load tokens from somewhere else, run: ```sh cat .custom/tags | unused --stdin ``` To view more usage options, run: ```sh unused --help ``` ## Troubleshooting ### Ctags (and a corresponding workflow) isn't configured [Exuberant Ctags] \(or another tool that will generate a tags file, like [hasktags] for Haskell projects) is required to use `unused` correctly; however, the version of `ctags` that ships with OS X (`/usr/bin/ctags`) is an older version won't work with many languages (that BSD version of `ctags` says it "makes a tags file for ex(1) from the specified C, Pascal, Fortran, YACC, lex, and lisp sources.") [hasktags]: https://hackage.haskell.org/package/hasktags Installation via Homebrew includes the `ctags` dependency. You can also run `brew install ctags` by hand. If you're not on OS X, use your favorite package manager and refer to the [Exuberant Ctags] site for download instructions. [Exuberant Ctags]: http://ctags.sourceforge.net/ #### Ctags manual run If you're using `ctags` to generate a `tags` file prior to running `unused` and don't have a workflow around automatically generating a `tags` file, run: ```sh git ls-files | xargs ctags -f tmp/tags ``` This will take your `.gitignore` into account and write the tags file to `tmp/tags`. Be sure to write this to a location that's ignored by `git`. While this process allows a developer to get started, it requires remembering to run this command before running `unused`. Let's explore how to automate this process. #### Ctags automatic runs via `git` hooks With `ctags` installed, you'll likely want to configure your workflow such that your tags file gets updated periodically without any action on your part. I recommend following the [instructions outlined by Tim Pope] on this matter, which discusses a workflow coupled to `git` for managing the tags file. It includes shell scripting that may not look "effortless"; however, the fact this is automated helps to ensure `unused` is running against new versions of the code as you (and other teammates, if you have any) are committing. As he suggests, you'll want to run `git init` into the directories you want this hook, and to manually run the hook: ```sh git ctags ``` `unused` is configured to look for a tags file in three different directories, including `.git/` as the article suggests, so no further configuration will be necessary with `unused`. [instructions outlined by Tim Pope]: http://tbaggery.com/2011/08/08/effortless-ctags-with-git.html ### "Calculating cache fingerprint" takes a long time `unused` attempts to be intelligent at understanding if your codebase has changed before running analysis (since it can be time-consuming on large codebases). To do so, it calculates a "fingerprint" of the entire directory by using `md5` (or `md5sum`), along with `find` and your `.gitignore` file. If you're checking in artifacts (e.g. `node_modules/`, `dist/`, `tmp/`, or similar), `unused` will likely take significantly longer to calculate the fingerprint. Per the `--help` documentation, you can disable caching with the `-C` flag: ```sh $ unused -C ``` ### "No results found" when expecting results If you're expecting to see results but `unused` doesn't find anything, verify that any artifacts `unused` uses (e.g. the `tags` file, wherever it's located) or generates (e.g. in `PROJECT_ROOT/tmp/unused`) is `.gitignore`d. What might be happening is, because unused searches for tokens with `ag` (which honors `.gitignore`), it's running into checked-in versions of the tokens from other files, resulting in duplicate occurrences that aren't representative of the actual codebase. The most obvious might be the `tags` file itself, although if you're using an IDE that runs any sort of analysis and that's getting checked in somehow, that may cause it too. One final piece to check is the number of tokens in the tags file itself; if `ctags` is misconfigured and only a handful of tokens are being analyzed, they all may have low removal likelihood and not display in the default results (high-likelihood only). ### Analysis takes a long time due to a large number of terms found In my experience, projects under 100,000LOC should have at most around 8,000 unique tokens found. This obviously depends on how you structure your classes/modules/functions, but it'll likely be close. If you're seeing more than 15,000 terms matched (I've seen upwards of 70,000), this is very likely due to misconfiguration of `ctags` where it includes some amount of build artifacts. In Ruby, this might be a `RAILS_ROOT/vendor` directory, or if you're using NPM, `APP_ROOT/node_modules` or `APP_ROOT/bower_components`. When configuring `ctags`, be sure to include your `--exclude` directives; you can [find an example here]. [find an example here]: https://github.com/joshuaclayton/dotfiles/commit/edf35f2a3ca2204a7c6796c3685b7da34bddf5fb#diff-6d7e423e99befb791a7db6ae51126747R76 ## Custom Configuration The first time you use `unused`, you might see a handful of false positives. `unused` will look in two additional locations in an attempt to load additional custom configuration to help improve this. ### Configuration format ```yaml # Language or framework name # e.g. Rails, Ruby, Go, Play - name: Framework or language # Collection of matches allowed to have one occurrence autoLowLikelihood: # Low likelihood match name - name: ActiveModel::Serializer # Flag to capture only capitalized names # e.g. would match `ApplicationController`, not `with_comments` classOrModule: true # Matcher for `.*Serializer$` # e.g. `UserSerializer`, `ProjectSerializer` termEndsWith: Serializer # Matcher for `^with_.*` # e.g. `with_comments`, `with_previous_payments` termStartsWith: with_ # Matcher for `^ApplicationController$` termEquals: ApplicationController # Matcher for `.*_factory.ex` # e.g. `lib/appname/user_factory.ex`, `lib/appname/project_factory.ex` pathEndsWith: _factory.ex # Matcher for `^app/policies.*` # e.g. `app/policies/user_policy.rb`, `app/policies/project_policy.rb` pathStartsWith: app/policies # list of termEquals # Matcher allowing any exact match from a list allowedTerms: - index? - edit? - create? ``` ### `~/.unused.yml` The first location is `~/.unused.yml`. This should hold widely-used configuration roughly applicable across projects. Here's an example of what might be present: ```yaml - name: Rails autoLowLikelihood: - name: ActiveModel::Serializer termEndsWith: Serializer classOrModule: true - name: Pundit termEndsWith: Policy classOrModule: true pathEndsWith: .rb - name: Pundit Helpers allowedTerms: - Scope - index? - new? - create? - show? - edit? - destroy? - resolve - name: JSONAPI::Resources termEndsWith: Resource classOrModule: true pathStartsWith: app/resources - name: JSONAPI::Resources Helpers allowedTerms: - updatable_fields pathStartsWith: app/resources ``` I tend to work on different APIs, and the two libraries I most commonly use have a fairly similar pattern when it comes to class naming. They both also use that naming structure to identify serializers automatically, meaning they very well may only be referenced once in the entire application (when they're initially defined). Similarly, with Pundit, an authorization library, naming conventions often mean only one reference to the class name. This is a file that might grow, but is focused on widely-used patterns across codebases. You might even want to check it into your dotfiles. ### `APP_ROOT/.unused.yml` The second location is `APP_ROOT/.unused.yml`. This is where any project-specific settings might live. If you're working on a library before extracting to a gem or package, you might have this configuration take that into account. ### Validation `unused` will attempt to parse both of these files, if it finds them. If either is invalid either due to missing or mistyped keys, an error will be displayed. ## Requirements Unused leverages [Ag](https://github.com/ggreer/the_silver_searcher) to analyze the codebase; as such, you'll need to have `ag` available in your `$PATH`. This is set as an explicit dependency in Homebrew. Alternatively, if you'd like to use [RipGrep](https://github.com/BurntSushi/ripgrep), you can do so with the `--search rg` flag. Be sure to have RipGrep installed first. ## Testing To run the test suite, run: ```sh stack test ``` ## License Copyright 2016-2018 Josh Clayton. See the [LICENSE](LICENSE).