Fix replace_keycodes has expr traceback

[ubitux]

Fixes the following traceback:
E5108: Error executing lua: ...site/pack/packer/start/nvim-cmp/lua/cmp/utils/keymap.lua:250: "replace_keycodes" requires "expr"
stack traceback:
[C]: in function 'nvim_set_keymap'
...site/pack/packer/start/nvim-cmp/lua/cmp/utils/keymap.lua:250: in function 'set_map'
...site/pack/packer/start/nvim-cmp/lua/cmp/utils/keymap.lua:170: in function 'solve'
...site/pack/packer/start/nvim-cmp/lua/cmp/utils/keymap.lua:133: in function <...site/pack/packer/start/nvim-cmp/lua/cmp/utils/keymap.lua:132>

Happens by simple pressing tab in insert mode on an empty file supported by a LSP.

Regression since 53bd574

[hrsh7th]

Sorry. I think it's not a valid fix. Could you create minimal reproduction step for your problem?

[ubitux]

Sorry. I think it's not a valid fix.

Yeah that's very likely I did something wrong

Could you create minimal reproduction step for your problem?

So I took https://raw.githubusercontent.com/hrsh7th/nvim-cmp/main/utils/vimrc.vim, added the following in the mapping (as recommended in nvim-cmp vimdoc)

    ['<Tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      else
        fallback()
      end
    end, { 'i', 's' }),

Then according to https://github.com/hrsh7th/vim-vsnip#2-setting I wanted to have:

imap <expr> <Tab>   vsnip#jumpable(1)   ? '<Plug>(vsnip-jump-next)'      : '<Tab>'
smap <expr> <Tab>   vsnip#jumpable(1)   ? '<Plug>(vsnip-jump-next)'  

Which I translated into lua as such:

vim.keymap.set({'i','s'}, '<Tab>', [[vsnip#jumpable(1) ? '<Plug>(vsnip-jump-next)' : '<Tab>']], {expr=true, remap=true})

Now for some reason the vim version doesn't cause the issue, but the lua one does, and it seems related to remap=true. Since the vimscript wasn't using inoremap/snoremap I thought that was the correct thing to do.

Anyway, here is the minimal configuration:

if has('vim_starting')
  set encoding=utf-8
endif
scriptencoding utf-8

if &compatible
  set nocompatible
endif

let s:plug_dir = expand('/tmp/plugged/vim-plug')
if !filereadable(s:plug_dir .. '/plug.vim')
  execute printf('!curl -fLo %s/autoload/plug.vim --create-dirs https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim', s:plug_dir)
end

execute 'set runtimepath+=' . s:plug_dir
call plug#begin(s:plug_dir)
Plug 'hrsh7th/nvim-cmp'
Plug 'hrsh7th/cmp-buffer'
Plug 'hrsh7th/cmp-nvim-lsp'
Plug 'hrsh7th/vim-vsnip'
Plug 'neovim/nvim-lspconfig'
call plug#end()
PlugInstall | quit

" Setup global configuration. More on configuration below.
lua << EOF
vim.keymap.set({'i','s'}, '<Tab>', [[vsnip#jumpable(1) ? '<Plug>(vsnip-jump-next)' : '<Tab>']], {expr=true, remap=true})

local cmp = require "cmp"
cmp.setup {
  snippet = {
    expand = function(args)
      vim.fn["vsnip#anonymous"](args.body)
    end,
  },

  mapping = {
    ['<CR>'] = cmp.mapping.confirm({ select = true }),
    ['<Tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      else
        fallback()
      end
    end, { 'i', 's' }),
  },

  sources = cmp.config.sources({
    { name = "nvim_lsp" },
    { name = "buffer" },
    { name = "vsnip" },
  }),
}
EOF

lua << EOF
local capabilities = require('cmp_nvim_lsp').default_capabilities()

require'lspconfig'.clangd.setup {
  capabilities = capabilities,
}
EOF

Repro:

1. nvim -u /tmp/vimrc.vim /tmp/test.c
2. go in insert mode
3. press <Tab>