cmp cmdline and group_index wont work

[JoseConseco]

According to docs using
src[x].group_index = 1,
src[y].group_index = 2,
Means that src[y] will get ignored if we src[x] will output any completion results. But It does not seem to work on cmp_cmdline plug. Setup:

cmp.setup.cmdline(":", {
  formatting = {
    format = function(entry, vim_item)
      vim_item.kind = lspkind.presets.default[vim_item.kind] .. " " .. vim_item.kind
      vim_item.abbr = vim.fn.strcharpart(vim_item.abbr, 0, 50) -- hack to clamp cmp-cmdline-history len
      vim_item.menu = ({
        cmdline_history = "[HIST]",
        cmdline = "[CMD]",
        fuzzy_path = "[PATH]",
        buffer = "[BUFF]",
      })[entry.source.name]
      return vim_item
    end,
  },
  sources = cmp.config.sources {
    { name = "cmdline_history", priority = 2, group_index=2 },
    { name = "cmdline", priority = 2, group_index=1 },
    { name = "fuzzy_path", priority = 1, group_index=2 }, -- from tzacher
    { name = "buffer", priority = 1, group_index=2 },
  },
})

Any ideas why? I tried to setup it as:
{ name = "cmdline_history" option = {priority = 2, group_index=2} }
too, but then even sorting by priority wont work (group_index still seems ignored)

[msva]

the reason is in that you're using cmp.config.sources {} instead of just table ({}) as value of completion source.
If you'll go to the definition of this function, you'll see, it inserts group_index = 1) to every table inside ;)

[JoseConseco]

Just for reference this will work ok wit group_index:

  sources = {
    { name = "cmdline", priority = 2, group_index = 1 },
    { name = "cmdline_history", priority = 1, group_index = 1, max_item_count = 3 },
    { name = "path", priority = 1, group_index = 2 }, -- from tzacher
    -- { name = "buffer",          priority = 1, group_index = 1 },
  },