Prevent saving an "empty" session

[okuuva]

My use case is the following:

I want to autoload a session for the cwd at start if it exits. If not I want to open alpha dashboard. I have setup alpha not to start automatically and have the following function as on_autoload_no_session function:

local on_autoload_no_session = function()
  -- need to pass true (on_vimenter) so that alpha clears the unnamed buffer vim creates at start
  require("alpha").start(true)
end

The first run everything goes fine, alpha dashboard starts up:

(just noticed the typo in "Find sesssion" :))

Then I hit <leader>q which is bound to :qa! in the dashboard settings.

The next time I open nvim in the same cwd, persisted loads practically an empty session:

Here's the actual session.vim file saved:

let SessionLoad = 1
let s:so_save = &g:so | let s:siso_save = &g:siso | setg so=0 siso=0 | setl so=-1 siso=-1
let v:this_session=expand("<sfile>:p")
silent only
cd ~/gits/persisted.nvim
if expand('%') == '' && !&modified && line('$') <= 1 && getline(1) == ''
  let s:wipebuf = bufnr('%')
endif
let s:shortmess_save = &shortmess
if &shortmess =~ 'A'
  set shortmess=aoOA
else
  set shortmess=aoO
endif
argglobal
%argdel
set lines=61 columns=232
if exists('s:wipebuf') && len(win_findbuf(s:wipebuf)) == 0 && getbufvar(s:wipebuf, '&buftype') isnot# 'terminal'
  silent exe 'bwipe ' . s:wipebuf
endif
unlet! s:wipebuf
set winheight=1 winwidth=20
let &shortmess = s:shortmess_save
let s:sx = expand("<sfile>:p:r")."x.vim"
if filereadable(s:sx)
  exe "source " . fnameescape(s:sx)
endif
let &g:so = s:so_save | let &g:siso = s:siso_save
set hlsearch
nohlsearch
doautoall SessionLoadPost
unlet SessionLoad
" vim: set ft=vim :

What should've happened (imo) is that the alpha dashboard would've opened instead of this "session".

My question is: is there a way to prevent persisted from saving such an "empty" session?

[Oli]

Are you lazy loading the plugin? I use this for my config:

use({
  "olimorris/persisted.nvim",
  module = "persisted", -- For lazy loading
  config = function()
    require("persisted").setup()
    require("telescope").load_extension("persisted") -- To load the telescope extension
  end,
})

and my "Find Session" command calls require("persisted").load().

I take your point though that there could be times when an empty session is saved to disk. Defo a risk if you don't lazy load.

[okuuva]

Hmm, how would lazyloading work with autoloading sessions? My use case is that I want to load alpha dashboard if session autoload fails, my reasoning being that manually loading an existing session for the current workdir is an unnecessary extra step.

[Oli]

It wouldn't; misread that first part of the issue 😄. Really good use case btw.

I think there's two components we'd need:

• A global variable to inform other plugins (or your config) that no session has been autoloaded (a global variable feels like the cleanest way of doing this)
• The ability to ignore the alpha filetype, ensuring that a blank session is not saved to disk if you quit Neovim from the dashboard

Do you agree?

[okuuva]

That should do it, or at least I can't think of a reason why that wouldn't work.

[Oli]

I've marked this as an enhancement and will try and pick this up in a couple of weeks

[loqusion]

Another option is to use the return value of a callback (e.g. true or false) to determine whether a session should be auto-saved — that way, any condition can be implemented. We could either use the existing before_save or introduce a new callback like should_save or should_autosave, or perhaps even allow the user to pass a callback to the existing autosave as an alternative to a boolean. It shouldn't affect manual SessionSaves, of course.

[Oli]

@loqusion - really good suggestion! Much cleaner and will cover anyone's edge case. I've added this in the latest commit

[okuuva]

That's really nice, works like a charm and makes it easy to update if there's more conditions in the future! Takkâ ennuv!