https://github.com/nominolo/scion.git
git clone 'git://github.com/nominolo/scion.git'
Scion is a Haskell library that aims to implement those parts of a Haskell IDE which are independent of the particular front-end. Scion is based on the GHC API and Cabal. It provides both a Haskell API and a server for non-Haskell clients such as Emacs and Vim.
(For developer builds see section “Hacking” below.)
Scion requires GHC 6.10.1 or later. All other dependencies should be on Hackage and can be installed using cabal-install. Scion consists of a library and a server which is used by front-ends that are not written in Haskell.
To install the library and server use:
$ cd dir/to/scion
$ cabal install
This will install the executable scion_server in the bin directory
of cabal-install, typically $HOME/.cabal/bin.
If you do not want to install the server (and its dependencies), turn off the “server” flag which is enabled by default:
$ cabal install -f-server
In order to use scion with your favourite front-end, see the specific instructions for the front-end below. The Emacs and Vim front-ends are included with Scion and their installation instruction follow below. The necessary files are installed with Scion by default and there is currently no option to turn this off.
Please send bug reports or feature requests to the Issue tracker.
Since Scion is a library, you should consult the haddock documentation for how to use it. However, you may look at the Emacs frontend for inspiration.
Scion's Emacs mode should be seen as complimentary to the existing Haskell mode. To use it install the Scion server as described above. In the following we'll assume that the server has been install as:
$ ~/.cabal/bin/scion-server
Add the following to your emacs configuration (typically “~/.emacs”):
;; Substitute the desired version for <version>
(add-to-list 'load-path "~/.cabal/share/scion-<version>/emacs")
(require 'scion)
;; if ./cabal/bin is not in your $PATH
(setq scion-program "~/.cabal/bin/scion-server")
(defun my-haskell-hook ()
;; Whenever we open a file in Haskell mode, also activate Scion
(scion-mode 1)
;; Whenever a file is saved, immediately type check it and
;; highlight errors/warnings in the source.
(scion-flycheck-on-save 1))
(add-hook 'haskell-mode-hook 'my-haskell-hook)
;; Use ido-mode completion (matches anywhere, not just beginning)
;;
;; WARNING: This causes some versions of Emacs to fail so badly
;; that Emacs needs to be restarted.
(setq scion-completing-read-function 'ido-completing-read)
Scion mode needs to communicate with the external server. By default the server will be started automatically when needed. See “Manually Connecting to Scion” below for how to connect to the server manually.
Scion uses Cabal as a library which in turn might look for external
programs such as happy or alex. In order to find these, the
PATH environment variable has to be set up correctly.
The scion server process inherits the environment variables from the
Emacs process. Depending on your system this may be different than
what you would get if you started the server from the shell. To
adjust the PATH environment variable from within Emacs, add
something like the following to your .emacs:
;; add ~/usr/bin to the PATH
(setenv "PATH" "$HOME/usr/bin:$PATH" t)
Once you have a running and connected Scion server, you can use the commands provided by scion-mode:
C-c C-x C-l (scion-load) load the current file with Scion. If
the file is within a Cabal project this will prompt to use the
settings from one of the components in the package description
file. You can still choose to load only the current file.
C-c C-o (scion-open-cabal-project) configures a Cabal project
and loads the meta-data from a Cabal file. Note that this
does not type check or load anything. If you change the Cabal
file of a project, call this function to update the session with
the new settings.
If loading generates any errors or warnings, a buffer will appear and
list them all. Pressing RET on a note will jump to its source
location. Pressing q closes the buffer, and C-c C-n
(scion-list-compiler-notes) brings it back. Use M-n
(scion-next-note-in-buffer) and M-p
(scion-previous-note-in-buffer) to navigate within the notes of one
buffer.
The following commands offer completion for a few things.
C-c i l (haskell-insert-language) asks for a LANGUAGE pragma
and adds it to the top of the file.
C-c i p (haskell-insert-pragma) inserts a pragma at the
current cursor position. (At the moment this doesn't try to make
sense of the selected pragma, however.)
C-c i m (haskell-insert-module-name) inserts the name of an
external module (external), i.e., a module not from the current
package.
C-c i f (haskell-insert-flag) insert (GHC) command line flag
at point. (Really only makes sense within an OPTIONS_GHC pragma.)
The following should work most of the cases.
C-c C-. (scion-goto-definition) jumps to the definition of the
identifier at point. If there is no identifier at point, offers a
list to complete on a particular identifier. This currently only
works for identifiers defined within the same project.
C-c C-t shows type of identifier at point. This only works if
the current file typechecks, but then it also works for local
identifiers. For polymorphic function it will show the type to
which they are instantiated, e.g.,
f x = x + (1::Int)
Calling this command on + will print Int -> Int -> Int instead
of Num a => a -> a -> a.
If you set the variable scion-auto-connect to 'ask (the default is
'always), Scion will ask whether to start the server. If you set it
to nil you need to manually connect to the server.
You can start the server manually on the command line and then use
M-x scion-connect
to connect to that server. However, most of the time it will be more convenient to start the server from within Emacs:
M-x scion
Vim mode requires Python support (version 2.4 or later). Vim 7.2 or later have Python support enabled by default. However, not every distribution of Vim includes a recent enough version of Python. Notably, MacVim is only linked against version 2.3.5 to be compatible with OS X 10.4. You will need to build it from source, which is however reasonably fast.
To check for python support the following should return 1:
:echo has('python')
To find out the version use:
:py import sys
:py print sys.version
Add the following to your ~/.vimrc (or only ~/.gvimrc if you have
different Vim versions). If Vim should start the Scion server itself
(recommended):
" recommended: vim spawns a scion instance itself:
let g:scion_connection_setting = [ 'scion', "<path/to/scion-server>"]
Note that there may be problems using “~” in the path, so better specify the absolute path.
If you want to connect to a running instance of the server via TCP,
add (where 4005 is the port number used by the scion server):
" use socket or TCP/IP connection instead:
let g:scion_connection_setting = [ 'socket', ["localhost", 4005] ]
Add the following independently of which connection mode you prefer:
set runtimepath+=<home>/.cabal/share/scion-<version>/vim_runtime_path/
Depending on your Vim config you will need to add the following lines as well:
:filetype plugin on
:source <home>/.cabal/share/scion-<version>/vim_runtime_path/plugin/haskell_scion.vim
You store certain settings in a configuration file. (Note: This feature is currently experimental and details may change in future Scion releases.) To generate an initial configuration file run
:WriteSampleConfigScion
Keep only these lines:
{"type":"build-configuration", "dist-dir":"dist-scion", "extra-args": []}
{"scion-default-cabal-config":"dist-scion"}
To load a component (a Cabal library or executable, or just a single file) use one of:
:LoadComponentScion library
:LoadComponentScion executable:cabal_executable_name
:LoadComponentScion file:cabal_executable_name
:LoadComponentScion
The last one is a shortcut for file:<this buf>. You can use completion.
At this point you should already get some compilation errors. After modifying the file, use
:BackgroundTypecheckFileScion
to re-typecheck just the current file.
If the file typechecks you can move the cursor onto an identifier and use the command
:ThingAtPointScion
You should see something like this, which is the (instantiated) type of the identifier at the point:
{'Just': 'print :: [Char] -> IO ()'}
Have a look at vim_runtime_path/ftplugin/haskell.vim to see a list of all
commands which are implemented yet.
BackgroundTypecheckFileScion should be called automatically after
buf write. If you don't like this set g:dont_check_on_buf_write or
overwrite g:haskell_qf_hook to change open/close quickfix and jump to
first error behaviour.
For discussions about Scion use the scion-lib-devel mailing list.
The main repository for Scion is hosted on Github. Get it via
$ git clone git://github.com/nominolo/scion
Send patches or pull requests to nominolo (email address at googlemail dot com). Note that, if you fork the project on Github your fork won't take up additional space on your account.
For development it is probably easier to use the GNU Make than Cabal
directly. The makefile includes a file called config.mk which is
not present by default. You can use the provided config.mk.sample
and edit it:
$ cp config.mk.sample config.mk
$ edit config.mk
After that, the makefile takes care of the rest.
$ make # configure and build
$ make install # configure, build, and install
GHC 6.10.1 has a couple of problems. For example, not all error
messages are reported using the GHC API but instead are printed to
stdout/stderr. Some parts also call exitWith directly. GHC's HEAD
branch has some of these bugs fixed and may contain new features not
present in the stable branch. If you want to compile against an
inplace GHC, the following steps should work:
On Windows, make sure that Cabal finds the inplace gcc
$ cd /path/to/ghc
$ cp `which gcc` ghc/
(Adjust to version of GCC that GHC was compiled with.)
Set the GHC_PATH variable to the correct path to for your
system. Make sure not to set HC, PKG, or HADDOCK, they
will automatically be set to point to the inplace versions.
Use make.
The parts of Scion written in Haskell are licensed under the BSD license. The Emacs lisp parts are licensed under the GPL license version 2 or (at your option) any later version.
If you get an error message like this: “scion_server: mkTopLevEnv: not interpreted main:Main” then you should rm [Ss]etup.hi [Ss]etup.o in the project directory.