refactor: use kwargs parameter in vim.split

runtime/lua/vim/shared.lua

@@ -98,20 +98,32 @@ end
 --- <pre>
 ---  split(":aa::b:", ":")     --> {'','aa','','b',''}
 ---  split("axaby", "ab?")     --> {'','x','y'}
----  split("x*yz*o", "*", true)  --> {'x','yz','o'}
----  split("|x|y|z|", "|", true, true) --> {'x', 'y', 'z'}
+---  split("x*yz*o", "*", {plain=true})  --> {'x','yz','o'}
+---  split("|x|y|z|", "|", {trimempty=true}) --> {'x', 'y', 'z'}
 --- </pre>
 ---
 ---@see |vim.gsplit()|
 ---
 ---@param s String to split
 ---@param sep Separator string or pattern
----@param plain If `true` use `sep` literally (passed to String.find)
----@param trimempty If `true` remove empty items from the front and back of the list
+---@param kwargs Keyword arguments:
+---       - plain: (boolean) If `true` use `sep` literally (passed to string.find)
+---       - trimempty: (boolean) If `true` remove empty items from the front
+---         and back of the list
 ---@returns List-like table of the split components.
-function vim.split(s, sep, plain, trimempty)
-  -- Only need to validate trimempty since the rest are validated by vim.gsplit
-  vim.validate{trimempty={trimempty, 'b', true}}
+function vim.split(s, sep, kwargs)
+  local plain
+  local trimempty = false
+  if type(kwargs) == 'boolean' then
+    -- Support old signature for backward compatibility
+    plain = kwargs
+  else
+    vim.validate { kwargs = {kwargs, 't', true} }
+    kwargs = kwargs or {}
+    plain = kwargs.plain
+    trimempty = kwargs.trimempty
+  end
+
   local t = {}
   local skip = trimempty
   for c in vim.gsplit(s, sep, plain) do