Automatically Reopen Previous Files and Session in Neovim

A common editor/IDE feature that most people probably don’t think about twice is that when you close down your editor and reopen it, you probably have the same files open, with the cursor at the same place, and mostly a duplicate experience of when you closed it.

Vim users know better though, and there’s a little more manual effort to that. With Vim, we have the idea of a session that handles this logic. So if you’re wanting to save the current session, you’d run mks[!]. This saves the session by default in a file named Session.vim. And then you reopen Vim you would have to run vim -s Session.vim to get back to where you were.

That’s great, but it’s very manual and I can never remember to run mks before close and -s on reopen.

Thankfully, Neovim is very approachable with configuring using Lua so I wanted to solve this since my recent migration from Vim to Neovim.

Note: This is very possible with Vim as well, but personally speaking Lua has opened up a ton more doors and interest in customizing my Vim experience.

I already had a vim bash function in my .bashrc, so I expanded it handle conditional logic on whether or not to automatically open up an existing session:

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vim () {
    if [[ -z "$@" ]]; then
	if [[ -f "./Session.vim" ]]; then
	    nvim -S Session.vim -c 'lua vim.g.savesession = true'
	else
	    nvim -c 'lua vim.g.savesession = true'
	fi
    else
    	nvim "$@"
    fi
}

When I open vim from the terminal, there is a bit of logic here that uses (or doesn’t use) an existing session. I also set some global state that I will refer back to soon.

If there are other parameters passed to Vim, I probably don’t want to use an existing session or save this one. For instance, if I’m in a random dir and want to quickly edit my bashrc, I’d probably do vim ~/.bashrc. Well, I don’t want that state to be saved, especially in that random dir. So I completely avoid state in that instance.

But if I just run vim, I probably want to automatically restore state (and save it on next exit).

In my Neovim config I have the following autocommand:

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vim.api.nvim_create_autocmd("VimLeavePre", {
  pattern = "*",
  callback = function()
    if vim.g.savesession then
      vim.api.nvim_command("mks!")
    end
  end
})

If vim.g.savesession is set then it runs mks before Vim exits. And that is set from my bash function when I don’t pass any parameters to vim.

So now I have a pretty modern approach to automatic state saving in Neovim with just a few extra lines of code!