Per-project formatter

[leana8959]

Hello,

I use both stylish-haskell and fourmolu to format my code. I like stylish-haskell for the vertical alignment and fourmolu for the diff-friendliness. I would like to have a way to switch between these two for projects in different contexts.

Is there an easy way to switch between the two? I have thought about creating an autocmd that toggles the option based on the project directory. The problem is that I don't know when exactly haskell-tools.nvim gets loaded, because my setting has to be loaded before it (right?)

Thanks for the help and have a nice day =)

[mrcjkb]

Hey 👋

haskell-tools doesn't do formatting. That's done by haskell-language-server, which has plugins for the for the different formatting providers.

For configuration via this plugin, see the advanced configuration section in the readme.

For haskell-language-server settings, see the hls documentation.

haskell-language-server loads the configuration at startup, and can't dynamically change the formatting provider at runtime.

If you only need different settings per project, you can use a hls.json (see this readme section).

To change the provider within a session, for the same project, you would have to change the configuration and then restart the LSP client with :HlsRestart (or vim.cmd.HlsRestart() in lua).

To change the configuration dynamically, you can do something like this:

vim.g.hls_formatting_provider = 'fourmolu'

vim.g.haskell_tools = {
  hls = {
    settings = function(project_root)
      local ht = require('haskell-tools')
      local defaults = ht.lsp.load_hls_settings(project_root)
      local result = vim.tbl_deep_extend('force', defaults, {
        haskell = {
          formattingProvider = vim.g.hls_formatting_provider,
        },
      })
      return result 
    end,
  },
}

And then define a command or keymap that sets vim.g.hls_formatting_provider and restarts haskell-language-server.

[leana8959]

Thank you for the help! I managed to got it work with your answer =)