How to format buffer on save (AstroNvim)

[nabiu256]

Checked other resources

• This is not a bug report or feature request (Please use issues for those).
• This is a question about rustaceanvim, not rust-analyzer or Neovim.
• This is not a question about autocompletion.
• I have read the README.
• I have read the FAQ.
• I have searched for a solution using :h rustaceanvim.
• I have searched existing discussions.
• I have searched the existing issues/discussions of other plugins related to this question (if applicable).
• I have searched the existing rust-analyzer discussions (if applicable).
• I have added a very descriptive title to this question.

Description

I'd like rustaceanvim to format my Rust buffers on save, which was the behaviour I had when using rust-analyzer through Mason. However, I have no idea how to achieve this.

Also, on a tip on the README.md it says

If you want to share keymaps with nvim-lspconfig, you can also use the vim.g.rustaceanvim.server.on_attach function, or an LspAttach autocommand.

However, I don't exactly know how to "use the vim.g.rustaceanvim.server.on_attach function", but I would like to get the formatting mapping that usually comes with nvim-lspconfig.

Any help?

Example Code

-- Astronvim config: lua/plugins/rustaceanvim.lua
vim.g.rustaceanvim = {
  server = {
    on_attach = function(_, bufnr)
      local utils = require "astrocore"
      local prefix = "<Leader>r"

      -- mappings...
    end,
  },
  tools = {
    test_executor = "background",
    float_win_config = {
      auto_focus = true,
    },
  },
}

---@type LazySpec
return {
  "mrcjkb/rustaceanvim",
  version = "^5", -- Recommended
  lazy = false, -- This plugin is already lazy
}

Neovim version (nvim -v)

v0.10.3

Operating system/version

Ubuntu 22.04

Output of :checkhealth rustaceanvim

==============================================================================
rustaceanvim: require("rustaceanvim.health").check()

Checking for Lua dependencies ~
- OK [mfussenegger/nvim-dap](https://github.com/mfussenegger/nvim-dap) installed.

Checking external dependencies ~
- OK rust-analyzer: found rust-analyzer 1.83.0 (90b35a6 2024-11-26)
- OK Cargo: found cargo 1.83.0 (5ffbef321 2024-10-29)
- OK rustc: found rustc 1.83.0 (90b35a623 2024-11-26)
- OK cargo-nextest: found cargo-nextest 0.9.87 (fee71ad7b 2024-12-17)
- OK debug adapter: found codelldb 

Checking config ~
- OK No errors found in config.

Checking for conflicting plugins ~
- OK No conflicting plugins detected.

Checking for tree-sitter parser ~
- OK tree-sitter parser for Rust detected.
- OK .vscode/settings.json loaded without errors.

[nabiu256]

Realized that I can add something like

      if client:supports_method "textDocument/formatting" then
        -- Format the current buffer on save
        vim.api.nvim_create_autocmd("BufWritePre", {
          buffer = bufnr,
          callback = function() vim.lsp.buf.format { bufnr = bufnr, id = client.id } end,
        })
        -- Add mapping for formatting
        utils.set_mappings {
          n = {
            ["<Leader>lf"] = { function() vim.lsp.buf.format { async = true } end, desc = "Format buffer" },
          },
        }
      end

on my rustaceanvim config and get what I wanted.

However, I still wonder if there's an easy how to keymaps and other capabilities that lspconfig sets up automatically? I'd rather not have my config file be so long.

[mrcjkb]

neither rustaceanvim, lspconfig or mason implement format on save. It must be another plugin, like lsp-zero.

See also:

• Autoformat on save not working #28 (comment)

[nabiu256]

neither rustaceanvim, lspconfig or mason implement format on save. It must be another plugin, like lsp-zero.

You're right! Hadn't noticed that it was AstroNvim that was configuring the format on save feature (I'm a bit rusty when it comes to nvim config).

For anyone that might find themselves in my situation, simply use AstroNvim's on_attach function in rustaceanvim's config, like so:

on_attach = function(client, bufnr)
  local astrolsp = require "astrolsp"

  -- Run AstroNvim default `on_attach` function to get regular LSP config
  astrolsp.on_attach(client, bufnr)
     
  -- other config...