feat(util): added Snacks.util.on_module to execute a callback when a module loads (or immediately when already loaded)

lua/snacks/util.lua

@@ -119,7 +119,6 @@ function M.blend(fg, bg, alpha)
 end
 
 local transparent ---@type boolean?
-
 --- Check if the colorscheme is transparent.
 function M.is_transparent()
   if transparent == nil then
@@ -158,4 +157,39 @@ function M.redraw(win)
   end
 end
 
+local mod_timer = assert((vim.uv or vim.loop).new_timer())
+local mod_cb = {} ---@type table<string, fun(modname:string)[]>
+
+---@return boolean waiting
+local function mod_check()
+  for modname, cbs in pairs(mod_cb) do
+    if package.loaded[modname] then
+      mod_cb[modname] = nil
+      for _, cb in ipairs(cbs) do
+        cb(modname)
+      end
+    end
+  end
+  return next(mod_cb) ~= nil
+end
+
+--- Call a function when a module is loaded.
+--- The callback is called immediately if the module is already loaded.
+--- Otherwise, it is called when the module is loaded.
+---@param modname string
+---@param cb fun(modname:string)
+function M.on_module(modname, cb)
+  mod_cb[modname] = mod_cb[modname] or {}
+  table.insert(mod_cb[modname], cb)
+  if mod_check() then
+    mod_timer:start(
+      100,
+      100,
+      vim.schedule_wrap(function()
+        return not mod_check() and mod_timer:stop()
+      end)
+    )
+  end
+end
+
 return M