Nill value when try to get vim undo directory about init.lua HOT 2 OPEN

To fix the "attempt to concatenate a nil value" on Windows, you need to create an environment variable set to your home directory; I recommend you make this under your User environment variables rather than System environment variables.

Something like "C:\Users\waleedrana777". Once you have the "HOME" environment variable set, you can restart your terminal, and it will work just fine. You don't need to create the "/.vim/undodir" folder either; once your HOME env variable is set, nvim will automatically create those folders for you.

In case you haven't worked with environment variables in Windows before, I recommend following this video to accomplish what I described above: https://www.youtube.com/watch?v=5BTnfpIq5mI

from init.lua.

I also followed a few weeks ago the tutorial, and the undo history has worked with this set of options (it is also on my dotfiles):

vim.o.swapfile = false
vim.o.backup = false
vim.o.undodir = os.getenv("HOME") .. "/.vim/undodir"
vim.o.undofile = true

If you are on Windows, you could try inverting the slashes on /.vim/undodir and see if It makes a difference.
About the autosave, you could bind Leader + Q to write and then quit all buffers (:wqa).
I have found a solution that allows me to create sessions that auto-save them when I need to, and load with a keybind. The cool thing is that, after created, they auto-save!
The plugin I used: rmagatti/auto-session
The code I used: here and the following keybinds (the first is from my dashboard plugin):

dashboard.button( "v", "    Source session",        ":SessionRestore<CR>"),

vim.keymap.set("n", "<leader>sd", "<cmd>SessionDelete<CR>", { desc = "Saved current session" })
vim.keymap.set("n", "<leader>sr", "<cmd>SessionRestore<CR>", { desc = "Restore session for CWD" })
vim.keymap.set("n", "<leader>ss", "<cmd>SessionSave<CR>", { desc = "Saved current session" })

Hope this helps! :)

from init.lua.