From 427939537da3c57ef90d5ebbd48605283e65f60b Mon Sep 17 00:00:00 2001
From: dlond <dlond@me.com>
Date: Fri, 30 May 2025 00:56:59 +1200
Subject: [PATCH] added some automation

---
 lua/custom/plugins/lsp/clangd.lua | 142 +++++++++++++++++++-----------
 1 file changed, 93 insertions(+), 49 deletions(-)

diff --git a/lua/custom/plugins/lsp/clangd.lua b/lua/custom/plugins/lsp/clangd.lua
index 1c8fe599..198d0f41 100644
--- a/lua/custom/plugins/lsp/clangd.lua
+++ b/lua/custom/plugins/lsp/clangd.lua
@@ -1,57 +1,101 @@
+local M = {}
+
+M.clang_filetypes = { 'c', 'cpp', 'objc', 'objcpp', 'cuda' }
+
+local lspconfig = require 'lspconfig'
+
+local function find_compile_commands()
+  local lines = vim.fn.systemlist { 'fd', '-u', '-t', 'f', 'compile_commands.json' }
+  table.sort(lines, function(a, b)
+    return a:match 'debug' and not b:match 'debug'
+  end)
+  return vim.fn.fnamemodify(lines[1] or '', ':h')
+end
+
+function M.stop_clangd()
+  for _, client in ipairs(vim.lsp.get_clients()) do
+    if client.name == 'clangd' then
+      client.stop()
+    end
+  end
+end
+
+function M.setup_clangd(commands_dir)
+  M.stop_clangd()
+
+  lspconfig.clangd.setup {
+    cmd = {
+      'clangd',
+      '--background-index',
+      '--clang-tidy',
+      '--header-insertion=never',
+      '--query-driver=' .. vim.fn.exepath 'clang++',
+      '--resource-dir=' .. vim.fn.systemlist({ 'clang++', '--print-resource-dir' })[1],
+      '--compile-commands-dir=' .. (commands_dir or '.'),
+    },
+    root_dir = lspconfig.util.root_pattern '.git',
+    single_file_support = true,
+    capabilities = require('blink.cmp').get_lsp_capabilities(),
+  }
+
+  for _, bufnr in ipairs(vim.api.nvim_list_bufs()) do
+    local ft = vim.api.nvim_buf_get_option(bufnr, 'filetype')
+    if vim.tbl_contains(M.clang_filetypes, ft) then
+      vim.lsp.buf_attach_client(bufnr, vim.lsp.get_active_clients({ name = 'clangd' })[1].id)
+    end
+  end
+end
+
+function M.pick_commands_dir()
+  local pickers = require 'telescope.pickers'
+  local finders = require 'telescope.finders'
+  local conf = require('telescope.config').values
+  pickers
+    .new({}, {
+      prompt_title = 'Choose compile_commands.json location',
+      finder = finders.new_oneshot_job { 'fd', '-u', 'compile_commands.json', '-x', 'dirname', '{}' },
+      sorter = conf.generic_sorter {},
+      attach_mappings = function(_, map)
+        map('i', '<CR>', function(prompt_bufnr)
+          local entry = require('telescope.actions.state').get_selected_entry()
+          local commands_dir = entry[1]
+          require('telescope.actions').close(prompt_bufnr)
+          reload_clangd(commands_dir)
+        end)
+        return true
+      end,
+    })
+    :find()
+end
+
+function M.watch_compile_commands()
+  local uv = vim.uv or vim.loop
+  local watcher = uv.new_fs_event()
+  local cwd = vim.fn.getcwd()
+
+  watcher:start(
+    cwd,
+    { recursive = true },
+    vim.schedule_wrap(function(_, fname, status)
+      if fname and fname:match 'compile_commands%.json$' and status.change then
+        watcher:stop()
+        M.setup_clangd(vim.fn.fnamemodify(fname, ':h'))
+      end
+    end)
+  )
+end
+
 return {
   'neovim/nvim-lspconfig',
-  ft = { 'c', 'cpp', 'objc', 'objcpp', 'cuda' },
+  ft = M.clang_filetypes,
   config = function()
-    local function build_cmd(commands_dir)
-      return {
-        'clangd',
-        '--background-index',
-        '--clang-tidy',
-        '--header-insertion=never',
-        '--query-driver=' .. vim.fn.exepath 'clang++',
-        '--resource-dir=' .. vim.fn.trim(vim.fn.system 'clang++ --print-resource-dir'),
-        '--compile-commands-dir=' .. commands_dir,
-      }
+    local dir = find_compile_commands()
+    if dir ~= '' then
+      M.setup_clangd(dir)
+    else
+      M.watch_compile_commands()
     end
 
-    local function reload_clangd(commands_dir)
-      commands_dir = commands_dir or './build/debug'
-      local lspconfig = require 'lspconfig'
-
-      lspconfig.clangd.setup {
-        cmd = build_cmd(commands_dir),
-        root_dir = lspconfig.util.root_pattern '.git',
-        single_file_support = true,
-        capabilities = require('blink.cmp').get_lsp_capabilities(),
-      }
-
-      vim.cmd.edit()
-    end
-
-    local function pick_commands_dir()
-      local pickers = require 'telescope.pickers'
-      local finders = require 'telescope.finders'
-      local conf = require('telescope.config').values
-      pickers
-        .new({}, {
-          prompt_title = 'Choose compile_commands.json location',
-          finder = finders.new_oneshot_job { 'fd', '-u', 'compile_commands.json', '-x', 'dirname', '{}' },
-          sorter = conf.generic_sorter {},
-          attach_mappings = function(_, map)
-            map('i', '<CR>', function(prompt_bufnr)
-              local entry = require('telescope.actions.state').get_selected_entry()
-              local commands_dir = entry[1]
-              require('telescope.actions').close(prompt_bufnr)
-              reload_clangd(commands_dir)
-            end)
-            return true
-          end,
-        })
-        :find()
-    end
-
-    reload_clangd()
-
     vim.keymap.set('n', '<leader>cc', pick_commands_dir, { desc = 'Pick location of compile_commands.json for clangd' })
   end,
 }