nested snippets help (porting from ultisnips)

[petobens]

Hi! I'm trying to port over my snippets from ultisnips. In particular I have the following ultisnip for tex files:

snippet up "Use Package" b
\usepackage${1:[${2:options}]}{${3:name}}
$0
endsnippet

which basically first selects [options] and then I can either erase that alltogether with backspace or jump into it and have the cursor in \usepackage[|]{name}. I'm trying to replicate such behaviour with luasnips as follows:

    s({ trig = 'up', dscr = 'Use package' }, {
        t('\\usepackage'),
        sn(1, {
            t('['),
            i(1, 'options'),
            t(']'),
        }),
        t('{'),
        i(2, 'name'),
        t('}'),
        i(0),
    }),

but I cannot seem to achieve the desired behaviour. Do I need to add a double nested snippet? Why is that when I press <backspace> I'm back into normal mode rather than insert mode?

Thanks in advance.

[ejmastnak]

This sounds like a good use case for a LuaSnip choice node. Here's an example where you choose between [options] (when you want to add package options) and an empty string (when you want only the package name).

  s({trig="up"},
    fmta(
      [[
        \usepackage<>{<>}
      ]],
      {
        c(1, {sn(nil, {t("["), i(1, "options"), t("]")}), t("")}),
        i(2, "name"),
      }
    )
  ),

Here's the snippet in action:

Slightly different behavior from what you posted, but I think it's in the spirit of what you're after. You could also modify the empty string text node t("") to something else if you prefer.

I cycle through the choice nodes by pressing a key (in my case Control-F for "forward") mapped to <Plug>luasnip-next-choice; as far as I know using choice-nodes is an opt-in feature and you have to manually set a key binding in your config, e.g.

  " Cycle forward through choice nodes with Control-F
  imap <silent><expr> <C-f> luasnip#choice_active() ? '<Plug>luasnip-next-choice' : '<C-f>'
  smap <silent><expr> <C-f> luasnip#choice_active() ? '<Plug>luasnip-next-choice' : '<C-f>'

(The LuaSnip README also has an example key binding for choice nodes.)

[Edit]

If you're porting from UltiSnips and use LaTeX, perhaps these resources might be useful:

• https://github.com/evesdropper/dotfiles/tree/main/nvim/luasnip#readme
• https://www.ejmastnak.com/tutorials/vim-latex/luasnip.html (self-plug)

[petobens]

Thanks for the reply and the excellent links. I'll thoroughly read them over the weekend.

So using choices is the best approximation I can get to the ultisnips behaviour of nested "deletable" (with backspace) snippets?

[ejmastnak]

Thanks for the reply and the excellent links. I'll thoroughly read them over the weekend.

Great, glad they seem useful!

So using choices is the best approximation I can get to the ultisnips behaviour of nested "deletable" (with backspace) snippets?

Oof, I personally can't guarantee choice nodes are the best approximation---there may well be something closer to your Ultisnips version. I just suggested the choice node because it seemed like a good fit for your situation, i.e. switching between two flavors of the same command, even if it's a new technique and muscle memory to get used to.

Perhaps someone else will chime in later with a better suggestion.

[L3MON4D3]

I'd also +1 the choiceNodes. It's possible to imitate ultisnips behaviour for nested placeholder with this (although it might not work anymore, been a while since I tried it last :sweat_smile:) (That function is intended for the parser_nested_assembler-setup-option, but you can just pass the placeholder-content into it as a snippetNode, and get the modified, selectable snippetNode)

[petobens]

Thanks to both of you for the help! Using choice nodes to mimic the previous behaviour. Closing