bug: ruff LSP format is not applied

[ahmedelgabri]

Neovim version (nvim -v)

0.11.1

Operating system/version

macOS 15.5

Read debugging tips

• I have read through the debugging tips.

Add the debug logs

• I have set log_level = vim.log.levels.DEBUG and pasted the log contents below.

Log file

Log file: /Users/ahmed/.local/state/nvim/conform.log
          2025-05-30 16:48:21[DEBUG] Run CWD: /Users/ahmed/Sites/personal/dev/file.py
          2025-05-30 16:48:21[DEBUG] ruff_fix exited with code 0
          2025-05-30 16:48:21[INFO] Run ruff_organize_imports on /Users/ahmed/Sites/personal/dev/file.py
          2025-05-30 16:48:21[DEBUG] Run command: { "/Users/ahmed/.local/bin/ruff", "check", "--fix", "--force-exclude", "--select=I001", "--exit-zero", "--no-cache", "--stdin-filename", "/Users/ahmed/Sites/personal/dev/file.py", "-" }
          2025-05-30 16:48:21[DEBUG] Run CWD: /Users/ahmed/Sites/personal/dev/ai-explorations
          2025-05-30 16:48:21[DEBUG] ruff_organize_imports exited with code 0
          2025-05-30 16:48:21[INFO] Run trim_whitespace on /Users/ahmed/Sites/personal/dev/file.py
          2025-05-30 16:48:21[INFO] Run trim_newlines on /Users/ahmed/Sites/personal/dev/file.py

Formatters for this buffer:
LSP: ruff
ruff_fix ready (python) /Users/ahmed/.local/bin/ruff
ruff_organize_imports ready (python) /Users/ahmed/.local/bin/ruff
trim_whitespace ready (*) 
trim_newlines ready (*) 

Other formatters:
alejandra ready (nix) /etc/profiles/per-user/ahmed/bin/alejandra
deno_fmt unavailable: Command 'deno' not found
goimports unavailable: Command 'goimports' not found
injected unavailable: Condition failed
jq ready (json) /run/current-system/sw/bin/jq
prettier ready (typescriptreact, graphql, less, scss, vue, json, markdown.mdx, jsonc, css, javascript, markdown, yaml, html, mdx, typescript.tsx, javascript.jsx, javascriptreact, typescript) /etc/profiles/per-user/ahmed/bin/prettier
shfmt ready (zsh) /etc/profiles/per-user/ahmed/bin/shfmt
statix ready (nix) /etc/profiles/per-user/ahmed/bin/statix
stylua ready (lua) /etc/profiles/per-user/ahmed/bin/stylua
taplo ready (toml) /etc/profiles/per-user/ahmed/bin/taplo

Describe the bug

I'm setting formatters for python as follows, because I'm using ruff as an LSP already. But when I save a file the LSP formatting doesn't run.

python = { 'ruff_fix', 'ruff_organize_imports', lsp_format = 'first' },

:=require('conform').list_formatters(0) doesn't show LSP in the list, but :ConformInfo shows it as enabled, but the logs doesn't show anything about formatting.

If I run vim.lsp.buf.format() it works, also require("conform").format({ bufnr = 0 }) works and I see this in the log file

2025-05-30 16:57:45[DEBUG] Running LSP formatter on /Users/ahmed/Sites/personal/dev/file.py
2025-05-30 16:57:45[DEBUG] Running formatters on /Users/ahmed/Sites/personal/dev/file.py: { "ruff_fix", "ruff_organize_imports", "trim_whitespace", "trim_newlines" }

What is the severity of this bug?

minor (annoyance)

Steps To Reproduce

1. nvim -u repro.lua file.py
2. save the file
3. file is not formatted

Expected Behavior

1. nvim -u repro.lua file.py
2. save the file
3. file is formatted

This is the output when running vim.lsp.buf.format() or require("conform").format({ bufnr = 0 })

import datetime


def foo():
    return datetime.time()


print(foo())

Minimal example file

import datetime












def foo():
























    return datetime.time()





















print(foo())

Minimal init.lua

-- 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",
		"--single-branch",
		"https://github.com/folke/lazy.nvim.git",
		lazypath,
	})
end

vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
	"folke/tokyonight.nvim",
	{
		"stevearc/conform.nvim",
		config = function()
			require("conform").setup({
				log_level = vim.log.levels.DEBUG,
				formatters_by_ft = {
					-- python = { lsp_format = "first" }, -- this also doesn't work
					python = { "ruff_fix", "ruff_organize_imports", lsp_format = "first" },
				},
			})
		end,
	},
	{
		"https://github.com/neovim/nvim-lspconfig",
		config = function()
			vim.lsp.config("*", {
				root_markers = { ".git" },
			})

			vim.lsp.config("ruff", {
				init_options = {
					settings = {
						configurationPreference = "filesystemFirst",
						fixAll = true,
						organizeImports = true,
						lint = {
							enable = true,
							preview = true,
						},
						format = {
							preview = true,
						},
					},
				},
			})

			vim.lsp.enable("ruff")
		end,
	},
}

require("lazy").setup(plugins, {
	root = root .. "/plugins",
})

vim.cmd.colorscheme("tokyonight")

Additional context

No response

[SavingFrame]

If you want to use ruff format then you need to add ruff_format into your formatters_by_ft.

[ahmedelgabri]

@SavingFrame, yes, I'm aware of this, but the plugin also supports LSP formatting, so technically, the LSP format should work because it's working for some of them but not all.