coc format behavior differently between Neovim and Vim, create unnecessary empty change in neovim. about coc.nvim

[towry]

It is this line causing the difference:

coc.nvim/src/model/document.ts

Line 349 in 2ec3166

this.nvim.resumeNotification(isCurrent, true)

[towry]

tracked down to line

coc.nvim/autoload/coc/compat.vim

Line 18 in 2ec3166

call nvim_buf_set_lines(a:bufnr, a:start, a:end, 0, a:replacement)

turns out when format without change, the arguments passed to nvim_buf_set_lines is (bufnr, 1, 1, 0, {})

And i test this function on a buffer, it did change the buffer and create empty change.

From :h nvim_buf_set_lines:

To insert lines at a given index, set start and end to the same index.
To delete a range of lines, set replacement to an empty array.

So (bufnr, 1, 1, 0, {}) will do nothing but make an empty change since a:start is same as a:end and replacement is empty.

[fannheyward]

Thank you for your tracking, but I can't reproduce this with your mini.nivm and formatted demo.lua, with coc-sumneko-lua on nvim nightly. And I couldn't reproduce with other language servers too.

[fannheyward]

The checking fix in #4995 is OK, but I couldn't result any format without change, coc.nvim couldn't run to this check.

[towry]

@fannheyward Just tested on different version of coc.

coc release branch coc.nvim version: 0.0.82-2ec31666 2024-04-23 09:10:14 +0800

have issue.

coc tag v0.0.82, v0.0.81 doesn't have issue.

[towry]

I believe this issue was introduced after v0.0.82.
another issue in format is that I have to use call CocAction('format') | sleep 1m to make it work in BufWritePre, otherwise the buf sometimes will be in dirty state.

But in v0.0.82, it works well without the need of sleep 1m.

You can discard this pr, and i will just stick to version v0.0.82.

[fannheyward]

I believe this issue was introduced after v0.0.82.

Thank you for your tests with different releases of coc, I don't complain your PR, but how to reproduce this, here's my tests:

1. mkdir -p test-4994
2. copy your mini.vim and demo.lua, and empty coc-settings.json. I've removed @statiolake/coc-stylua because sumneko-lua already supports formatting, no need to use stylus any more.
3. When tested with nvim 0.10.0 nightly, I need to add nvim-treesitter, otherwise, nvim reports highlighting error

augroup vimrc | autocmd! | augroup end

set nocompatible
set number
set laststatus=2

let g:coc_global_extensions = ['coc-sumneko-lua']
" change this to your local coc.nvim location.
set runtimepath^=/Users/fannheyward/.local/share/nvim/plugged/coc.nvim
set runtimepath^=/Users/fannheyward/.local/share/nvim/plugged/nvim-treesitter 
filetype plugin indent on
syntax on
autocmd BufWritePre * call CocAction('format')
command! -nargs=0 Format :call CocActionAsync('format')

set expandtab shiftwidth=4 tabstop=4 softtabstop=4

1. nvim -u mini.vim demo.lua, sumneko-lua reports unused local foo, the Lua LS is working
2. :call CocAction('format'), no changes
3. :Format, no changes
4. :w to fire autocmd, no changes
5. Tested with nvim 0.9.5 and 0.10.0 nightly, vim 9.1.0350, same results.

Also I've tested the formatting with tsserver, gopls, rust-analyzer servers, won't change on formatted files.

[fannheyward]

You can use coc.preferences.formatOnSave instead of BufWritePre.