Boot task to auto-format Clojure(Script) code



boot-fmt: auto-format Clojure(Script) code

Clojars Project

A boot task for automatically reformatting your source code, similar to golang's gofmt.


Beautiful machine-formatted source code saves you time, helps you find bugs, and avoids quibbles with collaborators. gofmt's success has shown that auto-formatting works for many golang teams; boot-fmt hopes to bring the same benefits to Clojure(Script).

Powered by zprint and clj-rewrite, boot-fmt aims to provide a friendly command-line interface.


With boot installed, you can use boot-fmt from any directory:

boot -d boot-fmt fmt -f src

Note that you do not need to use boot as your build tool or even have a build.boot present in the current directory. As long as boot is installed in your system, boot-fmt will work just fine even if your project is managed by leiningen.

However, if you do use boot as your build tool, you may add boot-fmt's coordinates as a dependency to your build.boot, e.g.:

(set-env! :dependencies '[[boot-fmt/boot-fmt "X.Y.Z" :scope "test"]])
(require '[boot-fmt.core :refer [fmt]])

Selecting files

There are three ways to select files to reformat. First, you can reformat all clj(s) files in the current git repository:

boot fmt --git

If you want to reformat a project managed by boot and have already set up a build.boot with :source-paths or :resource-paths, you can instruct boot-fmt to use these as its search path:

boot fmt --source

Finally, you can manually specify one more or more files or directories to scan. Directories are searched recursively for clj(s) source files:

boot fmt --files src

By specifying --files multiple times, you can add multiple files or directories to the search path. The --git, --source and --files can be combined.


Like gofmt, boot-fmt defaults to printing reformatted file contents to standard output. Generally boot-fmt can operate in four different modes: print, list, diff and overwrite. You can specify the operation to perform using the --mode parameter.

If your project is under source control (e.g. using git), a good option is to let boot-fmt overwrite files in the current repository:

boot fmt --git --mode overwrite --really

You can use git diff or git add -p to see what was changed and to manually confirm (or revert) reformated sections.

Note that overwriting files is potentially dangerous, so boot-fmt requires you to add the --really flag to indicate that you know what you're doing.

To preview changes, diff mode can be useful. Instead of overwriting files, diff mode prints a git-style diff to standard output:

boot fmt --git --mode diff

See the next section for a full description of each mode of operation.

Command line options

You can see the options available on the command line:

boot -d boot-fmt fmt --help

Here's the output:

Reformat Clojure(script) source files, like gofmt

Print reformatted source code to standard output. Parameters specified using
`-f` can be files or directories. Directories are scanned recursively for
Clojure(Script) source files.

Specify the operation using the --mode parameter:

--mode print (default)

Print reformatted code to standard output

--mode diff

When reformatted code is different from original, print diff to standard output.

--mode list

Where reformatted code is different from original, print filename standard output.

--mode overwrite

Overwrite files with reformatted code. As this is a potentially dangerous
operation, you need to specify the --really flag in addition to setting
the --mode parameter

  -h, --help          Print this help info.
  -m, --mode MODE     MODE sets mode of operation, i.e. print, list, diff or overwrite. Defaults to print.
  -r, --really        In overwrite mode, files are overwritten only if the --really flag is set as well
  -f, --files VAL     Conj VAL onto the list of files or directories to format
  -s, --source        Automatically scan for files in boot source-paths and resource-paths
  -g, --git           Automatically scan for files in current git repository
  -o, --options OPTS  OPTS sets zprint options.


The output of zprint (and of boot-fmt) can be customized extensively.

For example, the default behavior is to indent the first argument of function calls with double-space indentation:

- "supercalifragilisticexpialidocious")
+  "supercalifragilisticexpialidocious")

The Clojure Community Style Guide and Emacs's clojure-mode prefer single-space indentation in such contexts . If you prefer this community style over zprint's defaults, use the --options {:style :community} command line switch. See this list for other ways in which community style differs from the default style.

Using the --options switch you can also fine-tune indentation rules, including those for custom macros, by setting zprint options, for example:

boot fmt -f src --options '{:style :community, :fn-map {":require" :force-nl-body, "ns" :arg1-body}}'



  • Update to zprint 0.3.1


  • Update to zprint 0.2.12
  • Support cljs.hl extension (thanks @mariszo)


  • Update to zprint 0.2.10


  • Isolate dependencies in pods


  • Optionally scan for source files in current git repository
  • Optionally scan for source files in boot's :source-paths and :resource-paths


Copyright © 2016 Paulus Esterhazy

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