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goclj

Go tools for working with Clojure code.

Go Reference

The parse (doc) and format (doc) packages implement Clojure code parsing and (formatted) printing, respectively.

cljfmt is a command-line tool (inspired by gofmt) that uses format to read and reformat Clojure code. Because it parses the code, its formatting transformations are safe (they cannot change semantics).

Additionally, cljfmt applies various transformations to the code; these are discussed in the Transforms section, below.

To install or update, run

go install github.com/cespare/goclj/cljfmt@latest

(You'll need Go 1.16+.) Alternatively, you can download a clfjmt binary from the Releases page.

Here is the output of cljfmt -h:

usage: cljfmt [flags] [paths...]
Any directories given will be recursively walked. If no paths are provided,
cljfmt reads from standard input.

Flags:
  -c value
        path to config file (default /home/caleb/.cljfmt)
  -disable-transform value
        turn off the named transform (default none)
  -enable-transform value
        turn on the named transform (default none)
  -l    print files whose formatting differs from cljfmt's
  -w    write result to (source) file instead of stdout

See the goclj README for more documentation of the available transforms.

Transforms

Cljfmt can perform many different transformations on the parsed tree before emitting formatted code. These vary in how aggressive they are and whether they introduce the possibility of "false positives"; i.e., unwanted changes to code semantics. The default transformations are very safe. The non-default ones can be enabled with the -enable-transform command-line flag; after running one of these transformations, you should verify that the code did not break in some way (typically by running tests).

sort-import-require (default: on)

Sort :import and :require declarations in ns blocks.

enforce-ns-style (default: on)

Apply a few common ns style rules (based on How to ns):

  • Clauses use keywords (:require) rather than symbols (require)
  • Clauses are lists ((:require ...)) rather than vectors ([:require ...])
  • There is a newline after :require or :import
  • For :require specifically:
    • Each require is written as a vector, not a list
    • Each required namespace is written inside a vector (not a plain symbol)
    • :refered and :excluded items use vectors, not lists
  • For :import specifically:
    • Each import is written as a list, not a vector
    • Plain symbols become lists (java.util.Date becomes (java.util Date))

remove-trailing-newlines (default: on)

Remove extra newlines following sequence-like forms, so that parentheses are written on the same line. For example,

(foo bar
 )

becomes

(foo bar)

fix-defn-arglist-newline (default: on)

Move the arg vector of defns to the same line, if appropriate:

(defn foo
  [x] ...)

becomes

(defn foo [x]
  ...)

if there's no newline after the arg list.

fix-defmethod-dispatch-val-newline (default: on)

Move the dispatch-val of a defmethod to the same line, so that

(defmethod foo
  :bar
  [x] ...)

becomes

(defmethod foo :bar
  [x] ...)

remove-extra-blank-lines (default: on)

Consolidate consecutive blank lines into a single blank line.

fix-if-newline-consistency (default: on)

Ensure that if one arm of an if is on its own line, the other is as well. Either of these:

(if foo? a
  b)

(if foo?
  a b)

become

(if foo?
  a
  b)

use-to-require (default: off)

Consolidate :require and :use blocks inside ns declarations, rewriting them using :require if possible.

remove-unused-requires

Use simple heuristics to remove some probably-unused :require statements:

[foo :as x] ; if there is no x/y in the ns, this is removed
[foo :refer [x]] ; if x does not appear in the ns, this is removed

Cljfmt configuration

Cljfmt can optionally use a config file in one of these locations (in order of precedence):

  1. The path specified by the -c CLI argument
  2. The path specified by the CLJFMT_CONFIG_PATH environment variable
  3. $HOME/.cljfmt

This is a Clojure file containing a single map of options. Here's an example:

{:indent-overrides [; Compojure
                    ["GET" "POST" "PUT" "PATCH" "DELETE" "context"] :list-body
                    ; Korma
                    ["korma.core/select"
                     "korma.core/insert"
                     "korma.core/update"
                     "korma.core/delete"] :list-body]
 :thread-first-overrides ["-?>" :normal]}

The configuration map may use the following keys:

:extensions

This is a list of file extensions to format when cljfmt walks a directory.

If not set, the default list of extensions is

(".clj" ".cljs" ".cljc" ".edn")

:indent-overrides

This is used to customize the indentation rules that cljfmt applies to particular functions and macros. The value is a sequence of pairs; the first element of each pair is either a string or sequence of strings; the second element of the pair is the indentation rule to apply to the given names.

The names may be given with or without a qualifying namespace. If there is an indent-override for foo, it will apply to any list form starting with the symbol foo whether it's written as foo or ns/foo. If the indent-override is for my.ns/foo, then it only takes effect if:

  1. the symbol is written as my.ns/foo, or
  2. if the symbol is written as a/foo and there is a require containing [my.ns :as a], or
  3. the symbol is written as foo and there is a require containing [my.ns :refer [foo]].

The allowed indentation rules are as follows:

:normal is the default for sequences that introduce no indentation.

[1
 2]

:list is the default for lists. The first item of the subsequent line is aligned under the second element of the list.

(foobar 123
        456)

:list-body is for list forms which have bodies. Subsequent lines are indented by two spaces.

Examples of builtins which use :list-body indentation by default are fn, when, and most macros beginning with def.

(when-not (zero? x)
  (/ 1 x))

:let is for let-like forms. This is similar to :list-body, but additionally the first parameter is expected to be a let-style binding vector in which the even-numbered elements are indented by two spaces.

Examples of builtins that use :let by default are binding, dotimes, if-let, when-some, and loop.

(let [foobar
        (+ x 10)
      baz
        (+ y 20)]
  (* x y))

:for is for for-like forms. This is similar to :let, but additionally it supports having a :let clause with let-like binding vector formatted accordingly.

The builtins that use :for by default are for and doseq.

(for [x
        (range 5)
      :let [y
              (- 100 x)]
  (* x y))

:letfn is used for indenting letfn, where the binding vector contains function bodies that themselves should be indented as :list-body.

(letfn [(twice [x]
           (* x 2))
        (six-times [y]
           (* (twice y) 3))]
  (println "Twice 15 =" (twice 15))
  (println "Six times 15 =" (six-times 15)))

:deftype is used for macros similar to deftype that define functions/methods that themselves should be indented as :list-body.

Examples of builtins that use :deftype style by default are defprotocol, definterface, extend-type, and reify.

(defrecord Foo [x y z]
  Xer
  (foobar [this]
    this)
  (baz [this a b c]
    (+ a b c)))

:cond0 is similar to :list-body but the even-numbered arguments are indented by two spaces. By default this is used for cond.

(cond
  (> a 10)
    foo
  (> a 5)
    bar)

:cond1 is like :cond0 but it ignores the first argument when counting parameters for indentation. By default :cond1 is used for case, cond->, and cond->>.

(case x
  "one"
    1
  "two"
    2)

:cond2 is like :cond0 but it ignores the first two argument when counting parameters for indentation. By default :cond2 is used for condp.

(condp = value
  1
    "one"
  2
    "two"

:cond4 is like :cond0 but it ignores the first four argument when counting parameters for indentation.

:thread-first-overrides

This uses the same general paired format as :indent-overrides.

:thread-first-overrides allows specifying additional thread-first macro forms. The following varieties are allowed:

:normal is for typical thread-first macros such as -> and some->. They take one argument and then all subsequent arguments have a threaded first parameter.

:cond-> is for cond-> style threading, where every other argument is threaded (starting with the third one).