Vim plugin for Haskell development powered by the lightning fast
hdevtools background server.
About
hdevtools is a command line program
powered by the GHC API, that provides services for Haskell development.
hdevtools works by running a persistent process in the background, so that your
Haskell modules remain in memory, instead of having to reload everything each
time you change only one file. This is just like :reload in GHCi - with
hdevtools you get the speed of GHCi as well as tight integration with your
editor.
This is the Vim plugin that integrates Vim with hdevtools.
Requirements
The vim-hdevtools plugin requires a way to run hdevtools. Here are the
ways to make hdevtools available to the plugin.
Global hdevtools
Install the hdevtools command line program so that it is on your
executable $PATH.
Note that hdevtools must be built with the same version of GHC as the
project which you will be editing.
Local hdevtools with stack
If your project is built with stack and
if you run Vim from the directory that contains stack.yaml, then
the vim-hdevtools plugin can employ stack to automatically install
hdevtools built with the same version of GHC indicated by the resolver
in your stack.yaml. This will not conflict with any other installations
of hdevtools on your system.
If you want the vim-hdevtools plugin to use stack,
you have to enable this feature in your .vimrc like so:
let g:hdevtools_stack = 1
Installation
Install this plugin. pathogen.vim
is the recommended way:
cd ~/.vim/bundle
git clone https://github.com/bitc/vim-hdevtools.git
Configure your keybindings in your .vimrc file. I recommend something
like:
au FileType haskell nnoremap <buffer> <F1> :HdevtoolsType<CR>
au FileType haskell nnoremap <buffer> <silent> <F2> :HdevtoolsInfo<CR>
au FileType haskell nnoremap <buffer> <silent> <F3> :HdevtoolsClear<CR>
Features
Type Checking
The best feature of the hdevtools command is near-instant checking of Haskell
source files for errors - it's fast even for huge projects.
This Vim plugin does not have direct support for interacting with this feature.
Instead, I recommend using the excellent
Syntastic plugin.
Type Information
Position the cursor anywhere in a Haskell source file, and execute
HdevtoolsType (or press the <F1>) key if you have configured as above).
The type for the expression under the cursor will be printed, and the
expression will be highlighted. Repeated presses will expand the expression
that is examined.
To get information from GHC about the identifier under cursor,
execute HdevtoolsInfo (or press the <F2> key as configured above).
You can execute HdevtoolsClear to get rid of the highlighting.
Customization
You can set the g:hdevtools_options variable to pass custom options to
hdevtools.
This is useful for passing options through to GHC with the hdevtools -g
flag. For example, if your project source code is in a src directory,
and you want to use the GHC option -Wall, then stick the following somewhere
appropriate (such as your project's Session.vim):
let g:hdevtools_options = '-g-isrc -g-Wall'
Make sure that each GHC option has its own -g prefix (don't group multiple
options like this: "-g-isrc\ -Wall")
I recommend setting the flag to
defer GHC type errors to runtime,
so that Haskell expressions can be typechecked even if type errors
elsewhere in the project would otherwise prevent GHC from compiling.
let g:hdevtools_options = '-g-fdefer-type-errors'
Credits
Parts of the design of this plugin were inspired by
ghcmod-vim, and large amounts of
code were also taken.
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