borkdude / carve

Remove unused Clojure vars

Carve

Carve out the essentials of your Clojure app.

Rationale

Carve will search through your code for unused vars and will remove them.

Installation

Add to your deps.edn:

:aliases {
  ...
  :carve {:extra-deps {io.github.borkdude/carve {:git/url "https://github.com/borkdude/carve"
                                                 :git/sha "<SHA>"}}
          :main-opts  ["-m" "carve.main"]}
  ...
}

or to your bb.edn:

io.github.borkdude/carve {:git/url "https://github.com/borkdude/carve"
                          :git/sha "<SHA>"}

where the latest SHA can be found with:

$ git ls-remote https://github.com/borkdude/carve.git refs/heads/master

Babashka script

You can install carve as a babashka script that you can invoke as carve with:

$ bbin install io.github.borkdude/carve

See bbin for details.

Clojure tool

To use as a clojure tool:

$ clj -Ttools install io.github.borkdude/carve '{:git/tag "v0.3.5"}' :as carve

How does it work?

Carve invokes clj-kondo and uses the analysis information to check which vars are unused. To remove the relevant bits of code it uses rewrite-cljc.

Usage

The usage for a typical Clojure app looks like:

Babashka

To see help:

bb -x carve.api/carve! --help

To run with options:

bb -x carve.api/carve! --paths src test

Clojure

On the JVM:

clojure -M:carve --paths src test

You may provide options as an EDN literal with --opts, e.g.:

clojure -M:carve --opts '{:paths ["src" "test"] :report {:format :text}}'

To also load the config file in .carve/config.edn when passing --opts, set :merge-config:

clojure -M:carve --opts '{:interactive true :merge-config true}'

Clojure tool

As a clojure tool:

$ clj -Tcarve carve! '{:paths ["src"] :report true :report-format :text}'

Options

Run carve --help to see options.

You can also store the config for your project in .carve/config.edn. When invoking carve with no options, the options in .carve/config.edn will be used. When providing options, the CLI options will take precedence over the configuration in .carve/config.edn and the file will be ignored. Pass :merge-config from the CLI to also load and merge .carve/config.edn.

All options:

• :paths: a list of paths to analyze. Can be a mix of individual files and directories.
• :ignore-vars: a list of vars to ignore. Useful for when the analyzer has it wrong or you just want to keep the var for whatever reason.
• :api-namespaces: a list of namespaces of which only unused private vars will be reported.
• :carve-ignore-file: a file where ignored vars can be stored, .carve/ignore by default.
• :interactive: ask what to do with an unused var: remove from the file, add to .carve/ignore or continue. Set to true by default.
• :merge-config: Merge the CLI options and the config file together. Default is false.
• :out-dir: instead of writing back to the original file, write to this dir.
• :dry-run: just print the unused var expression.
• :aggressive: runs multiple times until no unused vars are left. Defaults to false.
• :report: when truthy, prints unused vars to stdout. Implies :dry-run true. The output format may be set using :report {:format ...} where format can be :edn, :text or :ignore. The text output can be interpreted by editors like Emacs. This option can be combined with :aggressive.
• :silent: when truthy, does not write to stdout. Implies :interactive false.
• :clj-kondo/config: a map of clj-kondo config opts that are passed on to clj-kondo, which is used to analyze usages. e.g.: passing {:skip-comments true} will ignore function usage in (comment) forms. Note that the config in .clj-kondo/config.edn is used as well - options passed with this key will override options set in the clj-kondo config file.

$ clojure -M:carve --paths "test-resources" --dry-run true
Carving test-resources/app.clj

Found unused var:
(defn unused-function [])

...

Carving test-resources/api.clj

Found unused var:
(defn- private-lib-function [])

...

$ clojure -M:carve --paths "test-resources"
Carving test-resources/app.clj

Found unused var:
(defn unused-function [])

Type Y to remove or i to add app/unused-function to .carve/ignore
n
Found unused var:
(defn another-unused-function [])

Type Y to remove or i to add app/another-unused-function to .carve/ignore
i
...

$ cat .carve/ignore
app/another-unused-function

Keep in mind that if you ran carve with {:paths ["src" "test"]}, there might still be potentially lots of unused code, which wasn't detected simply because there are tests for it.

So after a first cycle of carving you might want to do another run with simply {:paths ["src"]}, which will help deleting the rest of the unused code. Just beware that this will break all the tests using the code you just deleted, and you'll have to fix/delete them manually.*

Carve also removes any unused refers from namespace :require forms. This means any unused refer, not just refers for functions determined to be unused by carve.

CI integration

A good use case for Carve is the CI integration, to ensure that no one can introduce dead code into a codebase. This example shows how to add this step into CircleCI, but any other CI configuration will be similar.

First add this configuration into a .circleci/deps.edn file:

{:aliases
 {:carve {:extra-deps {io.github.borkdude/carve {:git/sha "$LATEST_CARVE_SHA"}}
          :main-opts ["-m" "carve.main"]}}}

Then configure your build step like this:

find_dead_code:
  working_directory: ~/$your-project
  docker:
    - image: circleci/clojure:openjdk-11-tools-deps

  steps:
    - checkout
    - run: mkdir -p ~/.clojure && cp .circleci/deps.edn ~/.clojure/deps.edn
    - run: clojure -M:carve --opts '{:paths ["src" "test"] :report {:format :text}}'

If the report step finds any dead code it exits with status code 1, thus failing the build step.

Emacs

carve.el

A simple emacs integration is provided by carve.el.

It lets you run carve with a simple key binding and opens a result buffer where you can navigate to the results and add them to your ignore file with a single keystroke.

Report mode

Running carve with in report mode (for example clojure -M:carve --paths src test --report true --report-format :text}') you can make all the links clickable by switching to compilation-mode.

Using :report-format :ignore returns the list of unused vars in the same format as .carve/ignore so you can create the initial ignore file or append to an existing one. For example with:

carve --paths "src" "test" --report true --report-format :ignore' > .carve/ignore

Articles

• Carve that Clojure codebase by Andrea Crotti

Dev

Running tests

If you want to run tests in Emacs and Cider you need to use the test alias, or it will fail while trying to load the test.check library. You can place this in your .dir-locals.el file in the root directory to always use the test alias:

((clojure-mode . ((cider-clojure-cli-global-options . "-R:test"))))

or alter the command used by cider-jack-in by prefixing the invocation with C-u.

License

Copyright © 2019-2023 Michiel Borkent

Distributed under the EPL License. See LICENSE.