Incorrect behaviour in cmdline completion

[yoursvivek]

Make sure you have done the following

• Updated to the latest version of blink.cmp
• Searched for existing issues and documentation (try <C-k> on https://cmp.saghen.dev)

Bug Description

When completing cmdline with :set foldmethod= completion shows up but when select_next/select_prev is issued using <C-N> or <DOWN> (or <C-P> or <UP>), existing word foldmethod= gets removed. Other keys like <C-Space>, <C-E>, etc work fine and don't remove existing word.

Bug is reproducible with only blink.cmp and lazy.nvim being only two plugins enabled.

Example:

Just after typing :set foldmethod=

After further typing <C-N>

Relevant configuration

---@module "blink.cmp"
---@type blink.cmp.Config
opts = {
  appearance = {
    use_nvim_cmp_as_default = true,
  },
  completion = {
    menu = {
      draw = {
        treesitter = { "lsp" },
        columns = { { 'kind_icon' }, { 'label', 'label_description', gap = 1 }, { "source_name", gap = 1 } },
      },
    },
    documentation = {
      auto_show = true,
    },
  },
  sources = {
    default = { "lsp", "path", "snippets", "buffer" },
  },
  signature = { enabled = true },
}

neovim version

NVIM v0.10.3 Build type: Release LuaJIT 2.1.1736781742 Run "nvim -V1 -v" for more info

blink.cmp version

commit b6f11a0

[emxxjnm]

same issue

2025-02-05.11.32.40.mov

[yoursvivek]

This also happens when one starts with V-Line mode and select suggestions, :'<,'> range gets removed entirely and replaced by suggestion.

@Saghen, if you could point me to suspected region in code base, I can take a stab at patching this.

[someoneinjd]

This bug was introduced by commit 9854978 :

@@ -81,14 +81,14 @@ function cmdline:get_completions(context, callback)

        -- remove prefix from the filter text
        local filter_text = completion
-       if has_prefix then filter_text = completion:sub(#current_arg_prefix + 1) end
+       if has_prefix and cmd == 'lua' then filter_text = completion:sub(#current_arg_prefix + 1) end

        -- for lua, use the filter text as the label since it doesn't include the prefix
        local label = cmd == 'lua' and filter_text or completion

        -- add prefix to the newText
        local new_text = completion
-       if not has_prefix then new_text = current_arg_prefix .. completion end
+       if not has_prefix and cmd == 'lua' then new_text = current_arg_prefix .. completion end

        table.insert(items, {
          label = label,

In this commit, to resolve #1075, the prefixes for all non :lua commands were ignored, which resulted in the various issues mentioned above. A more suitable approach might be to determine whether to ignore the prefix based on different completion types.