Haskell pretty printer
$ stack install hindent
$ hindent --help hindent --version --help --style STYLE --line-length <...> --indent-size <...> --no-force-newline [-X<...>]* [<FILENAME>] Version 5.1.1 Default --indent-size is 2. Specify --indent-size 4 if you prefer that. -X to pass extensions e.g. -XMagicHash etc. The --style option is now ignored, but preserved for backwards-compatibility. Johan Tibell is the default and only style.
hindent is used in a pipeline style
$ cat path/to/sourcefile.hs | hindent
The default indentation size is
2 spaces. Configure indentation size with
$ echo 'example = case x of Just p -> foo bar' | hindent --indent-size 2; echo example = case x of Just p -> foo bar $ echo 'example = case x of Just p -> foo bar' | hindent --indent-size 4; echo example = case x of Just p -> foo bar
.hindent.yaml file in your project directory or in your
~/ home directory. The following fields are accepted and are the
indent-size: 2 line-length: 80 force-trailing-newline: true line-breaks: [":>", ":<|>"] extensions: - DataKinds - GADTs - TypeApplications
By default, hindent preserves the newline or lack of newline in your input. With
force-trailing-newline, it will make sure there is always a trailing newline.
hindent can be forced to insert a newline before specific operators and tokens with
line-breaks. This is especially useful when utilizing libraries like
servant which use long type aliases.
extensions, hindent can be made aware of valid syntactic compiler extensions that would normally be considered invalid syntax.
It is also possible to specify which extensions HIndent runs
with in your
extensions: - MagicHash - RecursiveDo
hindent-mode, which provides keybindings to reindent parts of the
M-qreformats the current declaration. When inside a comment, it fills the current paragraph instead, like the standard
C-M-\reformats the current region.
To enable it, add the following to your init file:
(add-to-list 'load-path "/path/to/hindent/elisp") (require 'hindent) (add-hook 'haskell-mode-hook #'hindent-mode)
'formatprg' option lets you use an external program (like
hindent) to format your text. Put the following line into
~/.vim/ftplugin/haskell.vim to set this option for Haskell files:
Then you can format with hindent using
:help gq and
help 'formatprg' for more details.
Note that unlike in emacs you have to take care of selecting a sensible buffer region as input to hindent yourself. If that is too much trouble you can try vim-textobj-haskell which provides a text object for top level bindings.
In order to format an entire source file execute:
Alternatively you could use the vim-hindent plugin which runs hindent automatically when a Haskell file is saved.
Fortunately, you can use https://atom.io/packages/ide-haskell with the path to hindent specified instead of that to stylish-haskell. Works like a charm that way!
IntelliJ / other JetBrains IDEs
- Install the "HaskForce" Haskell plugin (this is so we get the language type recognized in the file watcher)
- Install the "File Watchers" plugin under "Browse Repositories"
- Add a File Watcher with
- File type: Haskell Language
- Immediate file synchronization: off
- Show console: Error
Now whenever you save a file,
hindent should autoformat it.