haskell-tools silently fails

[teto]

Neovim version (nvim -v)

master

Operating system/version

nixos unstable

Output of haskell-language-server-wrapper --version

No response

How to reproduce the issue

remove haskell-language-server from PATH

Expected behaviour

a notification error that neovim could not start the LSP server

Actual behaviour

line numbers may differ as I patched the plugin but my config calls start_or_attach in ftplugin/haskell.lua which triggers:

Error executing lua callback: ...neovim-unwrapped-1cc23e1/share/nvim/runtime/filetype.lua:21: Error executing lua: ...neovim-unwrapped-1cc23e1/share/nvim/runtime/filetype.lua:22: BufReadPost Autocommands for "*"..FileType Autocommands for "*"..function <SN
R>1_LoadFTPlugin[19]..script /home/teto/home/config/nvim/ftplugin/haskell.lua: Vim(runtime):E5113: Error while calling lua chunk: ...eto/neovim/haskell-tools.nvim/lua/haskell-tools/init.lua:72: attempt to call field 'start' (a nil value)                   
stack traceback:                                                                                                                                                                                                                                                
        ...eto/neovim/haskell-tools.nvim/lua/haskell-tools/init.lua:72: in function 'start_or_attach'                                                                                                                                                           
        /home/teto/home/config/nvim/ftplugin/haskell.lua:103: in main chunk                                            

Log files

No response

The minimal config used to reproduce this issue.

My interpretation of the bug is that haskell-tools checks if the lsp server is executable in lsp.setup() , which it was not in my case because LSP servers are available on a per-project (i.e., flake) basis and I was out of a project when I started neovim with a haskell file. Then HT gives up on the setup on this line

haskell-tools.nvim/lua/haskell-tools/lsp.lua

Line 105 in 4886a22

return

thus lsp.start() is never defined, which triggers my issue.
There is this in the log:

WARN | 2023-03-08 10:13:19 | ...teto/neovim/haskell-tools.nvim/lua/haskell-tools/lsp.lua:104 | Command haskell-language-server not found in PATH.

I think it would be better for HT to not check the presence of haskell-tools and leave neovim notify that it can't start the server.