cljfmt

cljfmt is a tool for formatting Clojure code idiomatically.

It can turn something like this:

( let [x 3
    y 4]
  (+ (* x x
  )(* y y)
  ))

Into nicely formatted Clojure code like this:

(let [x 3
      y 4]
  (+ (* x x) (* y y)))

However, it is not the goal of cljfmt to provide a canonical format.

Installation

The easiest way to get started with cljfmt is to add the lein-cljfmt plugin to your Leiningen project map:

:plugins [[lein-cljfmt "0.6.2"]]

cljfmt has tested on Leiningen 2.5, but may not work on older versions, particularly versions prior to Leiningen 2.4.

Usage

To check the formatting of your source files, use:

lein cljfmt check

If the formatting of any source file is incorrect, a diff will be supplied showing the problem, and what cljfmt thinks it should be.

If you want to check only a specific file, or several specific files, you can do that, too:

lein cljfmt check src/foo/core.clj

Once you've identified formatting issues, you can choose to ignore them, fix them manually, or let cljfmt fix them with:

lein cljfmt fix

As with the check task, you can choose to fix a specific file:

lein cljfmt fix src/foo/core.clj

Editor Support

• vim-cljfmt
• CIDER 0.9+
• Calva Clojure Formatter (VS Code)
• clojureVSCode (VS Code)

Configuration

You can configure lein-cljfmt by adding a :cljfmt map to your project:

:cljfmt {}

cljfmt has several different formatting rules, and these can be selectively enabled or disabled:

• :indentation? - true if cljfmt should correct the indentation of your code. Defaults to true.

• :remove-surrounding-whitespace? - true if cljfmt should remove whitespace surrounding inner forms. This will convert ( foo ) to (foo). Defaults to true.

• :remove-trailing-whitespace? - true if cljfmt should remove trailing whitespace in lines. This will convert (foo) \n to (foo)\n. Defaults to true.

• :insert-missing-whitespace? - true if cljfmt should insert whitespace missing from between elements. This will convert (foo(bar)) to (foo (bar)). Defaults to true.

• :remove-consecutive-blank-lines? - true if cljfmt should collapse consecutive blank lines. This will convert (foo)\n\n\n(bar) to (foo)\n\n(bar). Defaults to true.

You can also configure the behavior of cljfmt:

• :file-pattern - determines which files to scan, #”\.clj[csx]?$” by default.

• :indents - a map of var symbols to indentation rules, i.e. {symbol [& rules]}. See the next section for a detailed explanation.

  Unqualified symbols in the indents map will apply to any symbol with a matching "name" - so foo would apply to both org.me/foo and com.them/foo. If you want finer-grained control, you can use a fully qualified symbol in the indents map to configure indentation that applies only to org.me/foo:

  :cljfmt {:indents {org.me/foo [[:inner 0]]}}
  

  Configured this way, org.me/foo will indent differently from com.them/foo.

  Note that cljfmt currently doesn't resolve symbols brought into a namespace using :refer or :use - they can only be controlled by an unqualified indent rule.

  As with Leiningen profiles, you can add metadata hints. If you want to override all existing indents, instead of just supplying new indents that are merged with the defaults, you can use the :replace hint:

  :cljfmt {:indents ^:replace {#".*" [[:inner 0]]}}
  

• :alias-map - a map of namespace alias strings to fully qualified namespace names. This option is unnecessary in almost all cases, because cljfmt can compute the alias map from an ns declaration.

  However, it can't do that when used as a CLJS library, or when indenting something with no ns declaration like an EDN file. Even in those situations, you only need this option when using indentation rules that rely on the fully qualified symbol name.

  If you definitely need to configure this, it should look like this:

  :cljfmt {:indents {org.me/foo [[:inner 0]]}
           :alias-map {"me" "org.me"}}
  

Indentation rules

There are two types of indentation rule, :inner and :block.

Inner rules

An :inner rule will apply a constant indentation to all elements at a fixed depth. So an indent rule:

{foo [[:inner 0]]}

Will indent all elements inside a foo form by two spaces:

(foo bar
  baz
  bang)

While an indent rule like:

{foo [[:inner 1]]}

Will indent all subforms one level in:

(foo bar
 baz
 (bang
   quz
   qoz))

Sometimes it's useful to limit indentation to one argument of the surrounding form. For example, letfn uses inner indentation only in its binding vector:

(letfn [(double [x]
          (* x 2))]   ;; special indentation here
  (let [y (double 2)
        z (double 3)]
    (println y
             z)))     ;; but not here

To achieve this, an additional index argument may be used:

{letfn [[:inner 2 0]]}

This will limit the inner indent to depth 2 in argument 0.

Block rules

A :block rule is a little smarter. This will act like an inner indent only if there's a line break before a certain number of arguments, otherwise it acts like a normal list form.

For example, an indent rule:

{foo [[:block 0]]}

Indents like this, if there are more than 0 arguments on the same line as the symbol:

(foo bar
     baz
     bang)

But indents at a constant two spaces otherwise:

(foo
  bar
  baz
  bang)

License

Copyright © 2018 James Reeves

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.