Conflict with nvim-lspconfig v2.1.0

[Burtannia]

Neovim version (nvim -v)

v0.11.0

Operating system/version

NixOS 25.05

Output of :checkhealth haskell-tools

haskell-tools:                         require("haskell-tools.health").check()

Checking for Lua dependencies ~
- ✅ OK [nvim-telescope/telescope.nvim](https://github.com/nvim-telescope/telescope.nvim) installed.

Checking external dependencies ~
- ✅ OK haskell-language-server: found nix (Nix) 2.28.2
- ✅ OK hoogle: found Hoogle 5.0.18.4, https://hoogle.haskell.org/
- ✅ OK fast-tags: found fast-tags, version 2.0.2
- ✅ OK curl: found curl 8.12.1 (x86_64-pc-linux-gnu) libcurl/8.12.1 OpenSSL/3.4.1 zlib/1.3.1 brotli/1.1.0 zstd/1.5.7 libidn2/2.3.8 libpsl/0.21.5 libssh2/1.11.1 nghttp2/1.65.0
- ⚠️ WARNING haskell-debug-adapter: not found.
  Install [haskell-debug-adapter](https://github.com/phoityne/haskell-debug-adapter) for extended capabilities.
  Optional, for `dap` support.
  
- ⚠️ WARNING ghci-dap: not found.
  Install [ghci-dap](https://github.com/phoityne/ghci-dap) for extended capabilities.
  Optional, for `dap` support.
  

Checking config ~
- ✅ OK No errors found in config.

Checking for conflicting plugins ~
- ✅ OK No conflicting plugins detected.

How to reproduce the issue

1. Open a Haskell file.
2. Hit <leader>f to format.
3. Run :LspInfo

Expected behaviour

Formatted via fourmolu respecting the project's fourmolu.yaml. This was the behaviour before v5.0.0.

Expected no errors from :LspInfo.

Actual behaviour

Formatted via some default, presumably ormolu.

:LspInfo produces:

==============================================================================
vim.lsp:                                     require("vim.lsp.health").check()

- LSP log level : WARN
- Log path: /home/burtannia/.local/state/nvim/lsp.log
- Log size: 87974 KB

vim.lsp: Active Clients ~
- ❌ ERROR Failed to run healthcheck for "vim.lsp" plugin. Exception:
  Vim:E729: Using a Funcref as a String

I believe this is down to haskell-tools since running hls via lspconfig with an identical config works fine:

lspconfig.hls.setup({
	on_attach = on_attach,
	cmd = { "nix", "run", ".#hls", "--", "--lsp" },
	settings = {
		haskell = {
			formattingProvider = "fourmolu",
		},
	},
})

Log files

The minimal config used to reproduce this issue.

local on_attach = function(_, bufnr)
        bufmap("<leader>f", function()
		vim.lsp.buf.format({ async = true })
	end)
end

vim.g.haskell_tools = {
	hls = {
		on_attach = on_attach,
		cmd = { "nix", "run", ".#hls", "--", "--lsp" },
		settings = {
			haskell = {
				formattingProvider = "fourmolu",
			},
		},
	},
}

[mrcjkb]

Hey 👋

Some notes:

• cmd = { "nix", "run", ".#hls", "--", "--lsp" } is not something I can reproduce. Please see the troubleshooting section in the readme for how to create a minmal config (either with or without nix).
• :LspInfo is an nvim-lspconfig command, which is now an alias to :checkhealth vim.lsp. It's not implemented by haskell-tools.nvim.
• Vim:E729: Using a Funcref as a String is a Vimscript error regarding :h funcref. haskell-tools.nvim does not use vimscript and it doesn't use Funcrefs. So this error cannot originate from this plugin.
• If your formatting configs are not being respected, that's an issue with haskell-language-server, not haskell-tools.nvim.

[Burtannia]

@mrcjkb Hey, thanks for the response.

I'm not familiar with the inner workings of neovim or HLS, do you think that the :LspInfo error is coming from vim-lsp or from HLS? Or is it something specific to neovim itself?

[Burtannia]

Nevermind it appears I can't read...

The QuickStart guide for nvim-lspconfig has been updated and changed the configuration methods such that mine is no longer valid: https://github.com/neovim/nvim-lspconfig

I swear I must've read that document 10 times yesterday looking for a "migration to v0.11.0" section.

[Burtannia]

It seems as though the new config format doesn't work either so I'm going to open a bug report for neovim.

[Burtannia]

@mrcjkb Further to investigations in neovim/nvim-lspconfig#3809, it seems as though the issue arises when both haskell-tools and lspconfig (or something that depends on lspconfig) are installed. Previously, this didn't matter, as long as one followed the instructions and didn't manually configure HLS via lspconfig.

After recent changes, if both are installed at all, even with no additional config, it seems to create the :LspInfo error and also cause the different formatting behaviour.

Do you have any idea where to look to try and debug this further?

[mrcjkb]

Oh, I think I know what your issue is (at least regarding the formatter).

nvim-lspconfig has a lsp/hls.lua file that gets sourced automatically when the plugin is loaded:

https://github.com/neovim/nvim-lspconfig/blob/94d0fec9135719e046903bbbbf8f39e3d3436d4e/lsp/hls.lua#L26

haskell-tools.nvim version 5.0.0 uses vim.lsp.config('hls') (since https://github.com/mrcjkb/haskell-tools.nvim/commit/53d9888aebe27cd50c0404d88a7aa51d7341784a) and merges it with the config you pass to vim.g.haskell_toolsThe config fromvim.lsp.config('hls')` takes precedence.

I suppose I could change haskell-tools to use vim.lsp.config("haskell-tools") instead, to avoid conflicts.