neovim-ghci

Interactive Haskell development using GHCi in Neovim

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This is a fork of intero-neovim that uses regular GHCi, instead of intero. It has fewer features than its Intero counterpart, but does not rely on Stack and Intero.

Some key features:

• On-the-fly Typechecking

  This plugin reports errors and warnings as you work on your file using the Neomake plugin. Errors appear asynchronously, and don't block the UI.

• Built-in REPL

  Work with your Haskell code directly in GHCi using Neovim :terminal buffers. Load your file and play around with top-level functions directly.

Installing

This plugin is compatible with pathogen, vim-plug, etc. For example:

Plug 'owickstrom/neovim-ghci'

This plugin requires Cabal, 1.24.0 or higher. Optionally, install Neomake for error reporting.

Quickstart

• To open the REPL:
  • :GhciOpen
• To load into the REPL:
  • :GhciLoadCurrentFile
• To reload whatever's in the REPL:
  • :GhciReload
• To evaluate an expression from outside the REPL:
  • :GhciEvaluate <expression>, or
  • :GhciEvaluate, and then enter the expression in the prompt.

Usage

Complete usage and configuration information can be found in here:

:help ghci

Example Configuration

These are some suggested settings. This plugin sets up no keybindings by default.

augroup ghciMaps
  au!
  " Maps for ghci. Restrict to Haskell buffers so the bindings don't collide.

  " Background process and window management
  au FileType haskell nnoremap <silent> <leader>gs :GhciStart<CR>
  au FileType haskell nnoremap <silent> <leader>gk :GhciKill<CR>

  " Open GHCi split horizontally
  au FileType haskell nnoremap <silent> <leader>go :GhciOpen<CR>
  " Open GHCi split vertically
  au FileType haskell nnoremap <silent> <leader>gov :GhciOpen<CR><C-W>H
  au FileType haskell nnoremap <silent> <leader>gh :GhciHide<CR>

  " RELOADING (PICK ONE):

  " Automatically reload on save
  au BufWritePost *.hs GhciReload
  " Manually save and reload
  au FileType haskell nnoremap <silent> <leader>wr :w \| :GhciReload<CR>

  " Load individual modules
  au FileType haskell nnoremap <silent> <leader>gl :GhciLoadCurrentModule<CR>
  au FileType haskell nnoremap <silent> <leader>gf :GhciLoadCurrentFile<CR>
augroup END

" GHCi starts automatically. Set this if you'd like to prevent that.
let g:ghci_start_immediately = 0

" Customize how to run GHCi
let g:ghci_command = 'cabal new-repl'
let g:ghci_command_line_options = '-fobject-code'

Using the Stack REPL

If you'd like to use stack repl, instead of plain ghci or cabal repl, you can use something like the following configuration:

let g:ghci_command = 'stack repl'
let g:ghci_command_line_options = '--ghci-options="-fobject-code"'

Using a project specific .nvim.rc, you can also customize the Stack targets for the GHCi session of particular projects:

let g:ghci_command = 'stack repl my-project:test:my-test-suite'

Caveats

• Running :Neomake! directly will not work. You need to run :GhciReload instead.

• Some commands may have unexpected side-effects if you have an autocommand that automatically switches to insert mode when entering a terminal buffer.

Contributing

This project welcomes new contributions! Submit pull requests and open issues on GitHub: https://github.com/owickstrom/neovim-ghci

License

BSD3 License, the same license as ghcmod-vim and intero-neovim.