nvim/lua/plugins/conform.lua

-- Python/JS formatting rules, plus the on-save pipeline: every safe LSP code
-- action (import organizing, fix-alls, quickfixes) runs first, then conform
-- formats. Both hang off conform's `format_on_save` hook, which is the only
-- place the relative order is guaranteed; the action pass itself lives in
-- config.lsp_code_actions.

---@type LazySpec
return {
  -- ruff is both the import sorter and the formatter used for python below
  {
    "WhoIsSethDaniel/mason-tool-installer.nvim",
    optional = true,
    opts = function(_, opts)
      opts.ensure_installed = require("astrocore").list_insert_unique(opts.ensure_installed, { "ruff" })
    end,
  },
  {
    "stevearc/conform.nvim",
    opts = function(_, opts)
      -- Python: ruff sorts imports (I001), then reformats. ruff always emits
      -- 4-space indentation, so mixed tab/space indentation is normalized on
      -- save instead of surviving to raise TabError at runtime.
      if not opts.formatters_by_ft then opts.formatters_by_ft = {} end
      opts.formatters_by_ft.python = { "ruff_organize_imports", "ruff_format" }

      -- The pack's function returns nil when autoformat is toggled off
      -- (<Leader>uf buffer / <Leader>uF global), so one toggle governs the
      -- whole pipeline: no code actions and no formatting.
      local pack_format_on_save = opts.format_on_save
      opts.format_on_save = function(bufnr)
        -- NOT `f(bufnr) or f`: that resolves to the function itself when the
        -- call returns nil, and conform then gets a function as format opts
        local format = pack_format_on_save
        if type(format) == "function" then format = format(bufnr) end
        if not format then return end

        require("config.lsp_code_actions").apply(bufnr)

        -- Skip formatting JavaScript buffers (.js/.mjs/.cjs); the code actions
        -- above still run, and manual :Format / <Leader>lf still works.
        if vim.bo[bufnr].filetype == "javascript" then return end
        return format
      end
    end,
  },
}