mini.comment: change the default commentstring for a filetype

[krishna-bala]

I would like to change the default commentstring for c/cpp files from /* %s */ to // %s when using mini.comment. In the mini-comment.txt documentation, it mentions that

Comment structure is inferred from 'commentstring': either from current
buffer or from locally active tree-sitter language (only on Neovim>=0.9).

I am using neovim 0.9.0, so I believe the commentstring is inferred from the active tree-sitter language. Is there a way to modify the active tree-sitter language so that I can change the default commentstring for a given filetype?

[echasnovski]

I would like to change the default commentstring for c/cpp files from /* %s */ to // %s when using mini.comment. In the mini-comment.txt documentation, it mentions that

Comment structure is inferred from 'commentstring': either from current
buffer or from locally active tree-sitter language (only on Neovim>=0.9).

I am using neovim 0.9.0, so I believe the commentstring is inferred from the active tree-sitter language. Is there a way to modify the active tree-sitter language so that I can change the default commentstring for a given filetype?

Sure, by using one of the "usual" ways to modify 'commentstring' for a filetype:

• (highly suggested) Create an 'after/ftplugin/c.lua' file in your config directory (~/.config/nvim in Unix) and put vim.bo.commentstring = '// %s' there.
• Create autocommand for FileType event: au FileType c setlocal commentstring=//\ %s.

[krishna-bala]

Thank you, this was extremely helpful! Also thank you for the reddit post on after/ftplugin, that was also very helpful. The first suggestion solves the problem for me. However, my (modified) attempt at the second version didn't work -- I'm describing it below in case anyone is interested, but

feel free to ignore since the first suggestion works.

Here's how I tried to create an autocmmand for FileType event:
I'm using LazyVim, and therefore have my ~/.config/nvim structured per the LazyVim documentation like so:

|- ~/.config/nvim
   |- after/
      |- ftplugin/
         |- c.lua  (assume this is an empty file for this example)
   |- lua/
      |- config/
         |- autocmds.lua
         |- keymaps.lua
         |- lazy.lua
         |- options.lua
      |- plugins/
         |- ...

For configuring autocmds, the documentation says

The files autocmds.lua, keymaps.lua, lazy.lua and options.lua under lua/config will be automatically loaded at the appropriate time, so you don't need to require those files manually. LazyVim comes with a set of default config files that will be loaded before your own.

DANGER
Do not require autocmds, keymaps, lazy or options under lua/config/ or lazyvim.config manually. LazyVim will load those files automatically.

Therefore, I configured my autocmds.lua as follows:

-- Autocmds are automatically loaded on the VeryLazy event
-- Default autocmds that are always set: https://github.com/LazyVim/LazyVim/blob/main/lua/lazyvim/config/autocmds.lua
-- Add any additional autocmds here

local function augroup(name)
  return vim.api.nvim_create_augroup("lazyvim_config_" .. name, { clear = true })
end

vim.api.nvim_create_autocmd("FileType", {
  group = augroup("commentstring"),
  pattern = { "*.cc", "*.c", "*.h" },
  callback = function()
    vim.opt.commentstring = "// %s"
  end,
  desc = "Change commentstring for c/c++ files",
})

However, this does not seem to update the commentstring for *.cc, *.c, or *.h files.

[echasnovski]

However, this does not seem to update the commentstring for *.cc, *.c, or *.h files.

One problem here is that FileType takes actual filetype as pattern (see :h FileType). You can try pattern = { 'c', 'cpp' }.

[mangkoran]

I stumbled across this issue too and found this solution helpful. Don't mind me I just want to put the documentation regarding the "pattern" behaviour of "FileType" events 😅

Thank you for the solution!