feature request: use Ruff native language server for "ruff_format"

[steakhutzeee]

Did you check existing requests?

• I have searched the existing issues

Describe the feature

Actually ruff_format formatter does not work with the native ruff language server but only with the CLI.

Provide background

See issue on Ruff astral-sh/ruff#12514

What is the significance of this feature?

strongly desired

Additional details

My actual config is:

local M = {
  'stevearc/conform.nvim'
}

function M.config()
  require("conform").setup({
    formatters_by_ft = {
      -- python = {'ruff_organize_imports', 'ruff_format'},
    },
    format_after_save = {
      lsp_format = "fallback",
    },
    notify_on_error = true,
  })
end

return M

I'm not specifying any formatter in order to fall back to the LSP. This way I can format with the native Ruff server but I can't organize imports.

EDIT: Also added the following autocommand to sort imports:

vim.api.nvim_create_autocmd({ "BufWritePost" }, {
  pattern = { "*.py" },
  callback = function()
    vim.lsp.buf.code_action {
      context = {
        only = { 'source.organizeImports.ruff' },
      },
      apply = true,
    }
  end,
})

Maybe this can be integrated in Conform somehow?

[stevearc]

I don't think I understand what you are asking for. If you want to format using the ruff CLI, that's what the ruff_fix, ruff_format, and ruff_organize_imports formatters will do. If you want to format using the ruff LSP, then just attach the LSP and specify that conform should use LSP formatting. If you want to do organize imports + LSP formatting like in the issue you linked, you can do

python = { "ruff_organize_imports", lsp_format = "last" }

Does this cover your use case?

[steakhutzeee]

Thanks!

Was not aware of the "last" option. Silly question, and if I want to use the lsp to organize the imports instead of the CLI also?

In the issue I linked it was discouraged to fallback on lsp for formatting and use CLI for imports sorting. That's why I use the autocommand that calls the lsp for imports sorting also.

Also, how I format after save in this case with my config from above?

[stevearc]

You cannot use a LSP code action as a conform formatter. See #61 for an explanation of why LSP formatting is different from formatting CLI tools and why we have to handle it differently. Code actions have all the same issues as LSP formatting (operate on the current state of the buffer, modify the buffer directly instead of producing diffs). This makes them impossible to compose nicely with other formatters, and would require special handling.

It is possible that we could at some point add support for code actions as a formatting step that runs before LSP formatting, but it would be a significant amount of work and tricky to design a clean API. Until that happens, no code action formatters.

[steakhutzeee]

Thank you.

So my config should become:

local M = {
  'stevearc/conform.nvim'
}

function M.config()
  require("conform").setup({
    formatters_by_ft = {
      python = { 'ruff_organize_imports'},
      fish = {'fish_indent'},
    },
    format_after_save = {
      lsp_format = "last",
    },
    notify_on_error = true,
  })
end

return M

Or I need to also specify python = { "ruff_organize_imports", lsp_format = "last" } as you mentioned above?

[stevearc]

Either one should work

[steakhutzeee]

Out of curiosity. and if I would to use format on save only for some file types and not all of them?

[stevearc]

You can customize the format-on-save logic by providing a function. Here is a recipe with a bunch of ideas: https://github.com/stevearc/conform.nvim/blob/master/doc/recipes.md#autoformat-with-extra-features