fix(cabal): prevent error messages caused by external lsp plugins (#224)

Fixes #223 

###### Things done

- [x] Tested, as applicable:
  - [x] Manually
  - [ ] Added plenary specs
- [x] Updated
[CHANGELOG.md](https://github.com/MrcJkb/haskell-tools.nvim/blob/master/CHANGELOG.md)
(if applicable).
- [x] Fits
[CONTRIBUTING.md](https://github.com/MrcJkb/haskell-tools.nvim/blob/master/CONTRIBUTING.md)

Author: mrcjkb

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+### Fixed
+- Cabal: Do not advertise `server_capabilities` for `foldingRangeProvider`
+  and `selectionRangeProvider` ([#223](https://github.com/mrcjkb/haskell-tools.nvim/issues/223)).
+  Prevents error messages caused by plugins that provide LSP client capabilities that are
+  not built-in to Neovim.
+
 ## [1.11.1] - 2023-07-17
 ### Fixed
 - Hover: Fix error message when using go-to-definition/typeDefinition hover actions

lua/haskell-tools/lsp.lua

@@ -45,12 +45,12 @@ local commands = {
 ---GHC can leave behind corrupted files if it does not exit cleanly.
 ---(https://gitlab.haskell.org/ghc/ghc/-/issues/14533)
 ---To minimise the risk of this occurring, we attempt to shut down hls cleanly before exiting neovim.
----@param client number The LSP client
+---@param client lsp.Client The LSP client
 ---@param bufnr number The buffer number
 ---@return nil
 local function ensure_clean_exit_on_quit(client, bufnr)
   vim.api.nvim_create_autocmd('VimLeavePre', {
-    group = vim.api.nvim_create_augroup('haskell-tools-hls-clean-exit', { clear = true }),
+    group = vim.api.nvim_create_augroup('haskell-tools-hls-clean-exit-' .. tostring(client.id), { clear = true }),
     callback = function()
       ht.log.debug('Stopping LSP client...')
       vim.lsp.stop_client(client, false)
@@ -59,6 +59,22 @@ local function ensure_clean_exit_on_quit(client, bufnr)
   })
 end
 
+---A workaround for #48:
+---Some plugins that add LSP client capabilities which are not built-in to neovim
+---(like nvim-ufo and nvim-lsp-selection-range) cause error messages, because
+---haskell-language-server falsly advertises those server_capabilities for cabal files.
+---@param client lsp.Client
+---@return nil
+local function fix_cabal_client(client)
+  if client.name == lsp_util.cabal_client_name and client.server_capabilities then
+    client.server_capabilities = vim.tbl_extend('force', client.server_capabilities, {
+      foldingRangeProvider = false,
+      selectionRangeProvider = false,
+      documentHighlightProvider = false,
+    })
+  end
+end
+
 ---@class LoadHlsSettingsOpts
 ---@field settings_file_pattern string|nil File name or pattern to search for. Defaults to 'hls.json'
 
@@ -144,10 +160,11 @@ function lsp.setup()
       vim.notify('haskell-tools: ' .. msg, vim.log.levels.ERROR)
       return
     end
+    local is_cabal = filetype == 'cabal' or filetype == 'cabalproject'
     local project_root = ht.project.root_dir(file)
     local hls_settings = type(hls_opts.settings) == 'function' and hls_opts.settings(project_root) or hls_opts.settings
     local lsp_start_opts = {
-      name = lsp_util.client_name,
+      name = is_cabal and lsp_util.cabal_client_name or lsp_util.haskell_client_name,
       cmd = cmd,
       root_dir = project_root,
       capabilities = hls_opts.capabilities,
@@ -176,12 +193,13 @@ function lsp.setup()
           buf_refresh_codeLens()
         end
       end,
+      on_init = function(client, _)
+        ensure_clean_exit_on_quit(client, bufnr)
+        fix_cabal_client(client)
+      end,
     }
     ht.log.debug('LSP start options: lsp_start_opts')
     local client_id = vim.lsp.start(lsp_start_opts)
-    if client_id then
-      ensure_clean_exit_on_quit(client_id, bufnr)
-    end
     return client_id
   end
 

lua/haskell-tools/lsp/util.lua

@@ -13,11 +13,33 @@ local util = {}
 ---@diagnostic disable-next-line: deprecated
 util.get_clients = vim.lsp.get_clients or vim.lsp.get_active_clients
 
-util.client_name = 'haskell-tools.nvim'
+util.haskell_client_name = 'haskell-tools.nvim'
+util.cabal_client_name = 'haskell-tools.nvim (cabal)'
 
 ---@param bufnr number the buffer to get clients for
+---@return lsp.Client[] haskell_clients
+---@see util.get_clients
+function util.get_active_haskell_clients(bufnr)
+  return util.get_clients { bufnr = bufnr, name = util.cabal_client_name }
+end
+
+---@param bufnr number the buffer to get clients for
+---@return lsp.Client[] cabal_clinets
+---@see util.get_clients
+function util.get_active_cabal_clients(bufnr)
+  return util.get_clients { bufnr = bufnr, name = util.cabal_client_name }
+end
+
+---@param bufnr number the buffer to get clients for
+---@return lsp.Client[] ht_clients The haskell + cabal clients
+---@see util.get_clients
+---@see util.get_active_haskell_clients
+---@see util.get_active_cabal_clients
 function util.get_active_ht_clients(bufnr)
-  return util.get_clients { bufnr = bufnr, name = util.client_name }
+  local clients = {}
+  vim.list_extend(clients, util.get_active_haskell_clients(bufnr))
+  vim.list_extend(clients, util.get_active_cabal_clients(bufnr))
+  return clients
 end
 
 return util