chore(watchers): refactor events and make debouncer safe

- fs poll -> fs events
- make debouncer safe and fix diagnostics events

lua/nvim-tree/utils.lua

@@ -307,25 +307,57 @@ function M.key_by(tbl, key)
   return keyed
 end
 
----Execute callback timeout ms after the lastest invocation with context. Waiting invocations for that context will be discarded. Caller should this ensure that callback performs the same or functionally equivalent actions.
+local function timer_stop_close(timer)
+  if timer:is_active() then
+    timer:stop()
+  end
+  if not timer:is_closing() then
+    timer:close()
+  end
+end
+
+---Execute callback timeout ms after the lastest invocation with context.
+---Waiting invocations for that context will be discarded.
+---Invocation will be rescheduled while a callback is being executed.
+---Caller must ensure that callback performs the same or functionally equivalent actions.
+---
 ---@param context string identifies the callback to debounce
 ---@param timeout number ms to wait
 ---@param callback function to execute on completion
 function M.debounce(context, timeout, callback)
-  if M.debouncers[context] then
-    pcall(uv.close, M.debouncers[context])
+  -- all execution here is done in a synchronous context; no thread safety required
+
+  M.debouncers[context] = M.debouncers[context] or {}
+  local debouncer = M.debouncers[context]
+
+  -- cancel waiting or executing timer
+  if debouncer.timer then
+    timer_stop_close(debouncer.timer)
   end
 
-  M.debouncers[context] = uv.new_timer()
-  M.debouncers[context]:start(
-    timeout,
-    0,
-    vim.schedule_wrap(function()
-      M.debouncers[context]:close()
-      M.debouncers[context] = nil
+  local timer = uv.new_timer()
+  debouncer.timer = timer
+  timer:start(timeout, 0, function()
+    timer_stop_close(timer)
+
+    -- reschedule when callback is running
+    if debouncer.executing then
+      M.debounce(context, timeout, callback)
+      return
+    end
+
+    -- call back at a safe time
+    debouncer.executing = true
+    vim.schedule(function()
       callback()
+      debouncer.executing = false
+
+      -- no other timer waiting
+      if debouncer.timer == timer then
+        M.debouncers[context] = nil
+      end
     end)
-  )
+  end)
 end
 
 function M.focus_file(path)