Indent changes when using CoC, how do I stop this?

Question

I have set up my init.vim file to always use tabs as indentation by adding this to it:

set tabstop=4
set shiftwidth=4
set noexpandtab

Ever since I installed CoC to use Rust's language server, it indents with four spaces instead of tabs, overriding my init.vim. Whenever I open a file I have to run set noexpandtab, and if I have forgotten to do this I have to also run %retab! to fix any indentations that were made with spaces. I tried moving my tab configuration in init.vim to its very end thinking that this was probably some code in CoC that runs when the program starts, so I would override it with my config, but this didn't work.

How can I stop this?

Answer 1

Vim loads multiple files as described in :h :runtimepath.

In ftplugin/, you can add files like rust.vim where you define options for this filetype only. You may need to put the config in after/ftplugin to overwrite options set by other config files.

Considering this, a basic approach for your problem is to drop everything you rust-specific config in after/ftplugin/rust.vim.

However, you can go further and use (after/)indent/, (after/)compiler/ and so on, to organize your config even more.

Note that the options you set are not automatically restored. This can be a problem when the buffer's filetype changes: an option set for the first filetype will be preserved if it's not set for the second.

To avoid this problem, it's recommended to set the b:undo_ftplugin variable, to a value that resets each option you changed to its default. For an indent plugin, use b:undo_indent instead.

Putting it all together, you could have this in after/indent/rust.vim:

" set options locally
setlocal tabstop=4
setlocal shiftwidth=4
setlocal noexpandtab

" get a pre-existing `undo_indent` variable
let b:undo_ftplugin = get(b:, 'undo_indent', '')

" add a '|' to chain commands if `undo_indent` was set
if ! empty('b:undo_indent')
  let b:undo_indent .= ' | '
endif

" `set option< `restores `option` to its global value
" `.=` appends to the string
let b:undo_indent .=  "setlocal colorcolumn< foldmethod< suffixesadd< path<"