kibit

There's a function for that!

kibit is a static code analyzer for Clojure, ClojureScript, cljx and other Clojure variants. It uses core.logic to search for patterns of code that could be rewritten with a more idiomatic function or macro. For example if kibit finds the code

(if (some test)
  (some action)
  nil)

it will suggest using when instead:

(when (some test)
  (some action))

Usage

Add [lein-kibit "0.1.6"] to your :plugins vector in your :user profile. Then you can run

$ lein kibit

to analyze a Leiningen project's namespaces. Kibit will automatically pick up source paths from your project.clj from the following keyseqs: [:source-paths], [:cljsbuild :builds], and [:cljx :builds]. You can also run Kibit manually on individual files or folders (even if there is no Leiningen project.clj) by running:

$ lein kibit path/to/some/file.clj #or
$ lein kibit path/to/src/ #or
$ lein kibit path/to/src/clj/ path/to/src/cljs/util.cljs some/combo/of/files/and/folders.cljx

If you want to know how the Kibit rule system works there are some slides available at http://jonase.github.io/kibit-demo/.

Exit codes

If lein kibit returns any suggestions to forms then it's exit code will be 1. Otherwise it will exit 0. This can be useful to add in a build step for automated testing.

$ lein kibit
... suggestions follow

$ echo $?
1

Automatically rerunning when files change

You can use lein-auto to run kibit automatically when files change. Visit lein-auto's README for installation instructions. Note that this will run kibit over all of your files, not just the ones that have changed.

$ lein auto kibit
auto> Files changed: project.clj, [...]
auto> Running: lein kibit
... suggestions follow
auto> Failed.
auto> Files changed: test/my/test/misc.clj
auto> Running: lein kibit
... suggestions follow
auto> Failed.

Automatically replacing suggestions in source file

You can have kibit automatically apply suggestions to your source files.

Given a file:

(ns example)

(+ 1 a)

$ lein kibit --replace

will rewrite the file as:

(ns example)

(inc a)

Replacement can also be run interactively:

$ lein kibit --replace --interactive
 Would you like to replace
   (+ 1 a)
  with
   (inc a)
 in example.clj:3? [yes/no]

Reporters

Kibit comes with two reporters, the default plaintext reporter, and a GitHub Flavoured Markdown reporter. To specify a reporter, use the -r or --reporter commandline argument. For example:

lein kibit --reporter markdown
----
##### `test/project/core.clj:31`
Consider using:
```clojure
  (when true (println "hi"))
```
instead of:
```clojure
  (if true (do (println "hi")))
```

----
##### `test/project/core.clj:32`
Consider using:
```clojure
  (println "hi")
```
instead of:
```clojure
  (do (println "hi"))
```

which renders to:

---

test/project/core.clj:31

Consider using:

  (when true (println "hi"))

instead of:

  (if true (do (println "hi")))

...

Usage from inside Emacs

If you use Emacs for hacking Clojure, here's a way to use kibit from inside Emacs with all the fanciness you are used to from M-x compile. The kibit-helper package available from MELPA provides several handy commands. First, make sure you have MELPA available as a source of packages (which you may well already have done). As described in their Getting started section, put the following into your ~/.emacs:

(add-to-list 'package-archives
             '("melpa-stable" . "http://stable.melpa.org/packages/") t)

(If you want to be more on the cutting edge, you can include unreleased versions of packages using the non-stable URL, as explained in the MELPA instructions, but kibit-helper is also available from the less exciting stable repository.)

This will give you three new commands,

M-x kibit
M-x kibit-current-file
M-x kibit-accept-proposed-change

The first two cause the properly highlighted and hyperlinked kibit output to be presented in a *Kibit Suggestions* buffer. The third lets you automatically apply most of those suggestions to your source. (Suggestions which cite large blocks of code including comments cannot be automatically applied, as Kibit discards comments during processing.)

You will likely want to bind the last function to C-x C-` so it is easy to alternate with the next-error function (conventionally C-x `) as you walk through the suggestions made by Kibit:

(global-set-key (kbd "C-x C-`") 'kibit-accept-proposed-change)

Usage from inside vim (through Leiningen plugin)

kibit-vim allows you to analyze the current opened file by running:

:Kibit

Usage from inside vim (with vim-fireplace)

If you have vim-fireplace installed, you can use vim-kibit to run Kibit on your current buffer through the running REPL session.

vim-kibit is invoked by running:

:Kibit

Known limitations

Kibit reads source code without any macro expansion or evaluation. A macro can therefore easily invalidate a rule. Also, kibit will not know if the symbol + in the form (+ x 1) actually refers to a local or to a function in a namespace other than clojure.core. Expect some false positives.

Contributing

It is very easy to write new patterns for kibit. Take a look at control-structures.clj to see how new patterns are created. If you know of a recurring pattern of code that can be simplified, please consider sending me a pull request.

Bugs can be reported using the GitHub issue tracker.

Contributors

Thanks to all who have contributed to kibit!

TODO

• Leiningen project.clj setting for rule exclusion
• Leiningen project.clj setting for a directory of rules to include

License

Copyright © 2012 Jonas Enlund

Distributed under the Eclipse Public License, the same as Clojure.