149 lines
5.6 KiB
Markdown
149 lines
5.6 KiB
Markdown
# brittany [](https://hackage.haskell.org/package/brittany) [](https://www.stackage.org/package/brittany) [](http://travis-ci.org/lspitzner/brittany)
|
|
haskell source code formatter
|
|
|
|
|
|
|
|
(see [more examples and comparisons](/doc/showcases))
|
|
|
|
This project's goals roughly are to:
|
|
|
|
- Always retain the semantics of the source being transformed;
|
|
- Be idempotent (this also directly ensures that only valid haskell is
|
|
produced);
|
|
- Support the full GHC-haskell syntax including syntactic extensions
|
|
(but excluding `-XCPP` which is too hard);
|
|
- Retain newlines and comments unmodified;
|
|
- Be clever about using the available horizontal space while not overflowing
|
|
it if it cannot be avoided;
|
|
- Be clever about aligning things horizontally (this can be turned off
|
|
completely however);
|
|
- Have linear complexity in the size of the input.
|
|
|
|
In theory, the core algorithm inside brittany reaches these goals. It is rather
|
|
clever about making use of horizontal space while still being linear in the
|
|
size of the input (although the constant factor is not small). See
|
|
[these examples of clever layouting](/doc/showcases/Layout_Interactions.md).
|
|
|
|
But brittany is not finished yet, and there are some open issues that yet
|
|
require fixing:
|
|
|
|
- **only type-signatures and function/value bindings** are processed;
|
|
other module elements (data-decls, classes, instances, imports/exports etc.)
|
|
are not transformed in any way; this extends to e.g. **bindings inside class
|
|
instance definitions** - they **won't be touched** (yet).
|
|
- By using `ghc-exactprint` as the parser, brittany supports full GHC
|
|
including extensions, but **some of the less common syntactic elements
|
|
(even of 2010 haskell) are not handled**.
|
|
- **There are some known issues regarding handling of in-source comments.**
|
|
There are cases where comments are not copied to the output (this will
|
|
be detected and the user will get an error); there are other cases where
|
|
comments are moved slightly; there are also cases where comments result in
|
|
wonky newline insertion (although this should be a purely aesthetic issue.)
|
|
- ~~There is an **open performance issue on large inputs** (due to an
|
|
accidentally quadratic sub-algorithm); noticable for inputs with >1k loc.~~
|
|
(fixed in `0.8.0.3`)
|
|
|
|
# Other usage notes
|
|
|
|
- Supports GHC versions `8.0.*` and `8.2.*`.
|
|
- as of November'17, `brittany` is available on stackage nightly.
|
|
- config (file) documentation is lacking.
|
|
- some config values can not be configured via commandline yet.
|
|
- uses/creates user config file in `~/.brittany/config.yaml`;
|
|
also reads `brittany.yaml` in current dir if present.
|
|
|
|
# Installation
|
|
|
|
- via `cabal` "old-build"
|
|
|
|
~~~~.sh
|
|
# optionally:
|
|
# mkdir brittany
|
|
# cd brittany
|
|
# cabal sandbox init
|
|
cabal install brittany --bindir=$HOME/.cabal/bin # -w $PATH_TO_GHC_8_0
|
|
~~~~
|
|
|
|
- via `cabal new-build`
|
|
|
|
~~~~.sh
|
|
cabal unpack brittany
|
|
cd brittany-0.8.0.2
|
|
# cabal new-configure -w $PATH_TO_GHC_8_0
|
|
cabal new-build exe:brittany
|
|
# and it should be safe to just copy the executable, e.g.
|
|
cp `./find dist-newstyle/build/ -type f -name brittany` $HOME/.cabal/bin/
|
|
~~~~
|
|
|
|
- via `stack`
|
|
|
|
~~~~.sh
|
|
git clone https://github.com/lspitzner/brittany.git
|
|
cd brittany
|
|
stack install
|
|
~~~~
|
|
|
|
- via `aura` on ArchLinux
|
|
~~~~.sh
|
|
aura -A brittany
|
|
~~~~
|
|
|
|
# Usage
|
|
|
|
- Currently one mode of operation: Transform a single module. By default read
|
|
from `stdin` and written to `stdout`, but commandline arguments allow to
|
|
read/write from/to files.
|
|
- For stdin/stdout usage it makes sense to enable certain syntactic extensions
|
|
by default, i.e. to add something like this to your
|
|
`~/.brittany/config.yaml` (execute `brittany` once to create default):
|
|
|
|
~~~~
|
|
conf_forward:
|
|
options_ghc:
|
|
- -XLambdaCase
|
|
- -XMultiWayIf
|
|
- -XGADTs
|
|
- -XPatternGuards
|
|
- -XViewPatterns
|
|
- -XRecursiveDo
|
|
- -XTupleSections
|
|
- -XExplicitForAll
|
|
- -XImplicitParams
|
|
- -XQuasiQuotes
|
|
- -XTemplateHaskell
|
|
- -XBangPatterns
|
|
~~~~
|
|
|
|
# Feature Requests, Contribution, Documentation
|
|
|
|
This currently is a one-person project in the sense that 90% of the code is
|
|
written by one person. And (unfortunately) it is not my job to keep improving
|
|
this project. Please forgive that as a consequence my time to invest on new
|
|
features is rather limited.
|
|
|
|
Nonetheless I consider it "in active development" :)
|
|
|
|
One way of speeding things up is to make your own contributions. There is
|
|
a good amount of high-level documentation at
|
|
|
|
[the documentation index](doc/implementation/index.md)
|
|
|
|
Note that most development happens on the `dev` branch of this repository!
|
|
|
|
# License
|
|
|
|
Copyright (C) 2016-2017 Lennart Spitzner
|
|
|
|
This program is free software: you can redistribute it and/or modify
|
|
it under the terms of the
|
|
[GNU Affero General Public License, version 3](http://www.gnu.org/licenses/agpl-3.0.html),
|
|
as published by the Free Software Foundation.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU Affero General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Affero General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|