expr mapping + choice gives an error

[kraftwerk28]

The following mapping results in

E5108: Error executing lua: .../pack/packer/start/LuaSnip/lua/luasnip/nodes/snippet.lua:583: [LuaSnip Failed]: { "" }                                                                                                                  
stack traceback:
        [C]: in function 'error'
        .../pack/packer/start/LuaSnip/lua/luasnip/nodes/snippet.lua:583: in function 'set_text'
        ...ck/packer/start/LuaSnip/lua/luasnip/nodes/choiceNode.lua:238: in function 'no_region_check_wrap'
        ...nvim/site/pack/packer/start/LuaSnip/lua/luasnip/init.lua:310: in function 'change_choice'
        /home/kraftwerk28/.config/nvim/lua/plugins/luasnip.lua:73: in function ''
        vim/keymap.lua: in function <vim/keymap.lua:0>

vim.keymap.set({"s", "i"}, "<C-;>", function()
  if ls.choice_active() then
    ls.change_choice(1)
  else
    return "<C-;>"
  end
end, { silent = true, expr = true })

[L3MON4D3]

Yeah, I think there are some restrictions on which functions you're allowed to call with expr=true, and we call those :|
You can still map it via vimscript though:

imap <silent><expr> <C-E> luasnip#choice_active() ? '<Plug>luasnip-next-choice' : '<C-E>'
smap <silent><expr> <C-E> luasnip#choice_active() ? '<Plug>luasnip-next-choice' : '<C-E>'

imap <silent><expr> <C-T> luasnip#choice_active() ? '<Plug>luasnip-prev-choice' : '<C-T>'
smap <silent><expr> <C-T> luasnip#choice_active() ? '<Plug>luasnip-prev-choice' : '<C-T>'

(Something along those lines should work.)

[kraftwerk28]

Thank you. I also found that my code starts to work with vim.schedule (not sure if this going to cause any races though). I.e.

vim.keymap.set({"s", "i"}, "<C-;>", function()
  if ls.choice_active() then
    vim.schedule(function() ls.change_choice(1) end)
  else
    return "<C-;>"
  end
end, { silent = true, expr = true })

[L3MON4D3]

I think vim.schedule should be ok👍