lua function akin to https://github.com/onsails/lspkind.nvim/pull/30 but for Ultisnips

before.lua

local cmp = require('cmp')
local lspkind = require('lspkind')

--- Function to preview snippet before completion with nvim-cmp
---@param entry cmp.Entry
---@param vim_item vim.CompletedItem
---@return vim.CompletedItem
function CmpBefore(entry, vim_item)
    if entry.completion_item.snippet then
        local snippet_value = entry.completion_item.snippet.value
        local parsed_snippet = vim.lsp.util.parse_snippet(snippet_value)
        local snippet_preview = str.oneline(str.oneline(parsed_snippet))
        vim_item.abbr = snippet_preview
    else
        vim_item.abbr = entry:get_insert_text()
    end
    return vim_item
end

cmp.setup {
    -- ...
    formatting = {
        -- ...
        format = lspkind.cmp_format({
            before = CmpBefore
        })
    }
}