Error: Unknown function: UltiSnips#CanExpandSnippet, and it's workaround

[D029-W]

Greetings. I set up ultisnips' global variables, cmp_nvim_ultisnips, and neovim-cmp, in their respective order with Lazy.vim plug-in manager. (I will provide the full configuration code at the end.)

When I hit <tab> in a document, the following error pops up:

E5108: Error executing lua Vim:E117: Unknown function: UltiSnips#CanExpandSnippet
stack traceback:
[C]: at 0x55a4871cf190
...y/cmp-nvim-ultisnips/lua/cmp_nvim_ultisnips/mappings.lua:8: in function <...y/cmp-nvim-ultisnips/lua/cmp_nvim_ultisnips/mappings.lua:7>
...y/cmp-nvim-ultisnips/lua/cmp_nvim_ultisnips/mappings.lua:52: in function <...y/cmp-nvim-ultisnips/lua/cmp_nvim_ultisnips/mappings.lua:39>
...y/cmp-nvim-ultisnips/lua/cmp_nvim_ultisnips/mappings.lua:62: in function 'expand_or_jump_forwards' ~/.config/nvim/lua/plugins/nvim-cmp.lua:34: in function 'on_keymap'
.../.local/share/nvim/lazy/nvim-cmp/lua/cmp/core.lua:144: in function 'callback'
.../.local/share/nvim/lazy/nvim-cmp/lua/cmp/utils/keymap.lua:118: in function <.../.local/share/nvim/lazy/nvim-cmp/lua/cmp/utils/keymap.lua:112>
.../.local/share/nvim/lazy/nvim-cmp/lua/cmp/utils/keymap.lua:248: in function <.../.local/share/nvim/lazy/nvim-cmp/lua/cmp/utils/keymap.lua:247>

Based on Lazy.vim info panel, the ultisnips' version info and cmp-nvim-ultisnips' version info are here:

    ● ultisnips
        dir     ~/.local/share/nvim/lazy/ultisnips
        URL     https://github.com/SirVer/ultisnips
        version 3.2.0
        tag     3.2
        branch  master
        commit  7dc30c5
        ...

    ● cmp-nvim-ultisnips
        dir    ~/.local/share/nvim/lazy/cmp-nvim-ultisnips
        URL    https://github.com/quangnguyen30192/cmp-nvim-ultisnips
        branch main
        commit 2be0eda
        ...

The function 'UltiSnips#CanExpandSnippet' used in the mapping-related features for the "cmp-nvim-ultsnips" plugin is not available in this version of UltiSnips. Therefore, the following lines won't work:

    local cmp_ultisnips_mappings = require("cmp_nvim_ultisnips.mappings")
    local cmp = require("cmp")
    local cmp_opts = {
        -- Other options
        mapping = cmp.mapping.preset.insert({
            ["<Tab>"] = cmp.mapping(function(fallback)
                cmp_ultisnips_mappings.expand_or_jump_forwards(fallback)
            end, { "i", "s" }),
        }),
        -- Other options
    }

    cmp.setup(cmp_opts)

After researching a little bit, my workaround is using the method mentioned in :h UltiSnips-trigger-functions as follows:

        mapping = cmp.mapping.preset.insert({
            ["<Tab>"] = cmp.mapping(function(fallback)
                -- cmp_ultisnips_mappings.expand_or_jump_forwards(fallback)
                vim.fn["UltiSnips#ExpandSnippetOrJump"]()
                if vim.g.ulti_expand_or_jump_res == 0 then
                    -- Operation failed, input tab, and call fallback
                    vim.fn["feedkeys"](vim.api.nvim_replace_termcodes("<Tab>", true, true, true), 'n')
                    fallback()
                end
            end, { "i", "s" }),
            ["<S-Tab>"] = cmp.mapping(function(fallback)
                -- cmp_ultisnips_mappings.jump_backwards(fallback)
                vim.fn["UltiSnips#JumpBackwards"]()
                if vim.g.ulti_jump_backwards_res == 0 then
                    -- Operation failed, input tab, and call fallback
                    vim.fn["feedkeys"](vim.api.nvim_replace_termcodes("<S-Tab>", true, true, true), 'n')
                    fallback()
                end
            end, { "i", "s" }),
        }),

I hope this could help someone facing the same issue. Below are the codes I used. If there were better solutions or my code did not follow good practices, please mention it.

Sincerely

---

-- Ultisnips.lua
local function init()
    local snip_folder = '/.config/nvim/UltiSnips'

    vim.g.UltiSnipsExpandTrigger = '<Tab>'
    vim.g.UltiSnipsJumpForwardTrigger = '<Tab>'
    vim.g.UltiSnipsJumpBackwardTrigger = '<S-Tab>'
    vim.g.UltiSnipsSnippetDirectories = {(os.getenv("HOME") .. snip_folder), "UltiSnips"}

    -- Setup operation result variables for expand and jump operations
    vim.g.ulti_expand_or_jump_res = 0
    vim.g.ulti_jump_backwards_res = 0
end

return {
    "SirVer/ultisnips",
    version = "*",
    init = init,
    lazy = false,
}

-- nvim-cmp.lua
-- This file sets up auto-completion with Ultisnips and others
local function config()
    -- Load cmp_nvim_ultisnips plugin first
    local cmp_ultisnips = require("cmp_nvim_ultisnips")
    local cmp_ultisnips_opts = {
        filetype_source = "treesitter",
        show_snippets = "expandable",
        documentation = function(snippet)
            return snippet.description .. "\n\n" .. snippet.value
        end,
    }
    cmp_ultisnips.setup(cmp_ultisnips_opts)

    -- Config nvim-cmp
    -- local cmp_ultisnips_mappings = require("cmp_nvim_ultisnips.mappings")
    local cmp = require("cmp")
    local cmp_opts = {
        snippet = {
            expand = function(args)
                vim.fn["UltiSnips#Anon"](args.body)
            end,
        },
        -- windows = {
        --     -- completion = cmp.config.window.bordered(),
        --     -- documentation = cmp.config.window.bordered(),
        -- },
        mapping = cmp.mapping.preset.insert({
            ['<C-n>'] = cmp.mapping.select_next_item(),
            ['<C-p>'] = cmp.mapping.select_prev_item(),
            ['<C-d>'] = cmp.mapping.scroll_docs(3),
            ['<C-f>'] = cmp.mapping.scroll_docs(3),
            ['<CR>'] = cmp.mapping.confirm({ select = true }),
            ["<Tab>"] = cmp.mapping(function(fallback)
                -- cmp_ultisnips_mappings.expand_or_jump_forwards(fallback)
                vim.fn["UltiSnips#ExpandSnippetOrJump"]()
                if vim.g.ulti_expand_or_jump_res == 0 then
                    -- Operation failed, input tab, and call fallback
                    vim.fn["feedkeys"](vim.api.nvim_replace_termcodes("<Tab>", true, true, true), 'n')
                    fallback()
                end
            end, { "i", "s" }),
            ["<S-Tab>"] = cmp.mapping(function(fallback)
                -- cmp_ultisnips_mappings.jump_backwards(fallback)
                vim.fn["UltiSnips#JumpBackwards"]()
                if vim.g.ulti_jump_backwards_res == 0 then
                    -- Operation failed, input tab, and call fallback
                    vim.fn["feedkeys"](vim.api.nvim_replace_termcodes("<S-Tab>", true, true, true), 'n')
                    fallback()
                end
            end, { "i", "s" }),
        }),
        sources = cmp.config.sources({
            { name = 'ultisnips' },
            { name = 'nvim_lsp' },
        }, {
            { name = 'buffer' },
            { name = 'path' },
        }),
    }

    cmp.setup(cmp_opts)

    -- To use git you need to install the plugin petertriho/cmp-git and uncomment lines below
    -- Set configuration for specific filetype.
    --[[ cmp.setup.filetype('gitcommit', {
        sources = cmp.config.sources({
            { name = 'git' },
        }, {
            { name = 'buffer' },
        })
    })
    require("cmp_git").setup() ]]-- 

    -- Use buffer source for `/` and `?` (if you enabled `native_menu`, this won't work anymore).
    cmp.setup.cmdline({ '/', '?' }, {
        mapping = cmp.mapping.preset.cmdline(),
        sources = {
            { name = 'buffer' }
        }
    })

    -- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
    cmp.setup.cmdline(':', {
        mapping = cmp.mapping.preset.cmdline(),
        sources = cmp.config.sources({
            { name = 'path' }
        }, {
            {
                name = 'cmdline',
                option = {
                    ignore_cmds = { 'Man', '!' }
                },
            }
        }),
        matching = { disallow_symbol_nonprefix_matching = false }
    })

    -- -- Set up lspconfig.
    -- local capabilities = require('cmp_nvim_lsp').default_capabilities()
    -- -- Replace <YOUR_LSP_SERVER> with each lsp server you've enabled.
    -- require('lspconfig')['<YOUR_LSP_SERVER>'].setup {
    --     capabilities = capabilities
    -- }
end

return {
    "hrsh7th/nvim-cmp",
    dependencies = {
        "hrsh7th/cmp-nvim-lsp",
        "hrsh7th/cmp-cmdline",
        "hrsh7th/cmp-buffer",
        "hrsh7th/cmp-path",
        "SirVer/ultisnips",
        "quangnguyen30192/cmp-nvim-ultisnips",
        "neovim/nvim-lspconfig",
    },
    config = config,
    version = "*",
}