bug: Filetype is applied once for each line when redirecting command output

[jedrzejboczar]

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• [X] I have read all the noice.nvim docs
• [X] I have searched the existing issues of noice.nvim
• [X] I have searched the exsiting issues of plugins related to this issue

Neovim version (nvim -v)

NVIM v0.9.0-dev-784+g72f0c461a

Operating system/version

Arch Linux

Describe the bug

When using noice.redirect to display command output in a popup, it is very slow (e.g. over 1.2 seconds to display 50 lines on my system). After some debugging I found that it is due to constantly setting filetype for the buffer (View:render -> nui.nvim utils.set_buf_options). This option is being set on each displayed line, which in turn runs the following lines from ftplugin.vim, which is quite slow on my system and takes ~10ms for each call. Tested with:

local name = 'noice'
local start = vim.fn.reltime()
vim.cmd('runtime! ftplugin/' .. name .. '.vim ftplugin/' .. name .. '_*.vim ftplugin/' .. name .. '/*.vim')
vim.cmd('runtime! ftplugin/' .. name .. '.lua ftplugin/' .. name .. '_*.lua ftplugin/' .. name .. '/*.lua')
local elapsed = vim.fn.reltime(start)
print(string.format('Elapsed %.3f ms', vim.fn.reltimefloat(elapsed) * 1000)) -- "Elapsed 9.482 ms"

Steps To Reproduce

While in this repro it will not be slow because there are not many plugins in runtimepath, the following steps will show how many times the filetype option is being set:

• Use the provided repro.lua: nvim -u repro.lua, then exit
• Apply the following nui.patch: cd ./.repro/plugins/nui.nvim/ && git apply ../../../nui.patch

diff --git a/lua/nui/utils/init.lua b/lua/nui/utils/init.lua
index b1e4fbe..608039f 100644
--- a/lua/nui/utils/init.lua
+++ b/lua/nui/utils/init.lua
@@ -121,11 +121,17 @@ function _.clear_namespace(bufnr, ns_id, linenr_start, linenr_end)
   vim.api.nvim_buf_clear_namespace(bufnr, ns_id, linenr_start - 1, linenr_end - 1)
 end

+_G.dbg = {}
+
 ---@private
 ---@param bufnr number
 ---@param buf_options table<string, any>
 function _.set_buf_options(bufnr, buf_options)
   for name, value in pairs(buf_options) do
+    local opt_counts = _G.dbg[bufnr] or {}
+    opt_counts.__bufname = vim.api.nvim_buf_get_name(bufnr)
+    opt_counts[name] = (opt_counts[name] or 0) + 1
+    _G.dbg[bufnr] = opt_counts
     vim.api.nvim_buf_set_option(bufnr, name, value)
   end
 end

• Open nvim nvim -u repro.lua, type :TestCmd and hit <m-cr>
• It will show the output in a popup
• Run :lua = _G.dbg and hit <m-cr>
• It will show how many times filetype has been set for a buffer, which for one buffer should correspond to the number of message lines:

  [22] = {
    __bufname = "",
    buftype = 101,
    filetype = 101
  },

Expected Behavior

Maybe this is an issue with my setup with quite a lot of plugins, or maybe I have some plugin that makes the call to runtime! very slow - I am not sure, I'll try to investigate more. But still I think it should be expected that noice is not setting filetype on every output line.

Repro

-- DO NOT change the paths and don't remove the colorscheme
local root = vim.fn.fnamemodify("./.repro", ":p")
-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
  vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath, })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
  "folke/tokyonight.nvim",
  "folke/noice.nvim",
  'MunifTanjim/nui.nvim',
  -- add any other plugins here
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
})

vim.cmd.colorscheme("tokyonight")
-- add anything else here

require('noice').setup {}

local redirect = function()
  require('noice').redirect(vim.fn.getcmdline())
end
vim.keymap.set('c', '<m-cr>', redirect, { desc = 'Redirect Cmdline' })

vim.api.nvim_create_user_command('TestCmd', function()
  local msg = {}
  for i = 1, 100 do
    table.insert(msg, string.rep(' ', i % 10) .. 'Message ' .. i)
  end
  print(table.concat(msg, '\n'))
end, {})