hdevtools Vim Plugin

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.

Get it from Github: https://github.com/hdevtools/hdevtools/

Or from Hackage:

$ cabal install hdevtools

Or from Stackage:

$ stack install hdevtools

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

1. Install this plugin. pathogen.vim is the recommended way:

    cd ~/.vim/bundle
    git clone https://github.com/bitc/vim-hdevtools.git
   

2. 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.