Rust Extra

lang.rust adds Rust and TOML editor support. It assumes the Rust toolchain is managed outside Blak with rustup or your system package manager.

Enable it

-- ~/.config/blak/lua/blak/user.lua
return {
  extras = {
    enabled = {
      "lang.rust",
    },
  },
}

Or toggle it from Neovim:

:BlakExtras enable lang.rust

Run :BlakExtras sync after enabling because this extra adds a plugin.

What it adds

Surface	Contribution
Treesitter	rust, toml
LSP	rust_analyzer, taplo
Formatting	rustfmt with LSP fallback for rust; taplo with LSP fallback for toml
Plugins	saecki/crates.nvim for Cargo.toml

The extra configures rust-analyzer with cargo.allFeatures = true and check.command = "clippy".

Configure rust-analyzer

Add non-conflicting rust-analyzer settings in user.lua:

return {
  extras = {
    enabled = { "lang.rust" },
  },
  lsp = {
    servers = {
      rust_analyzer = {
        settings = {
          ["rust-analyzer"] = {
            procMacro = { enable = true },
            diagnostics = {
              disabled = { "unresolved-proc-macro" },
            },
          },
        },
      },
    },
  },
}

Your user.lua settings win over the extra’s defaults for the same keys, so ["rust-analyzer"] = { check = { command = "check" } } switches on-save checks from Clippy back to cargo check while keeping cargo.allFeatures.

Cargo.toml and crates.nvim

crates.nvim runs as an in-process language server in Cargo.toml, so it uses the regular LSP keymaps instead of adding its own:

Key	In Cargo.toml
K	Crate popup: description, links, versions
<leader>ca	Update, upgrade, or expand a crate; open docs, crates.io, or lib.rs
Insert mode	Completion for crate names, versions, and features

Outdated versions show the latest release as virtual text. :Crates exposes every other crates.nvim action, such as :Crates show_features_popup.

Configure formatting

The default uses external formatters where available and falls back to LSP:

return {
  extras = {
    enabled = { "lang.rust" },
  },
  format = {
    formatters_by_ft = {
      rust = { "rustfmt", lsp_format = "fallback" },
      toml = { "taplo", lsp_format = "fallback" },
    },
  },
}

Tooling notes

Install Rust itself outside Blak. Formatting and on-save checks use the toolchain’s rustfmt and Clippy:

rustup component add rustfmt clippy

Mason installs rust-analyzer and taplo for the LSP server list, and Mason’s binaries come first on Neovim’s $PATH, so the Mason rust-analyzer is used even when rustup also has one.

Debugging

Enable debug.dap as well and lang.rust registers CodeLLDB. Without debug.dap it is not installed; with it, Mason downloads codelldb (about 150 MB). The enable order does not matter.

With	Contribution
debug.dap	Mason codelldb; a codelldb adapter
debug.dap	Launch configuration Debug binary (cargo build)

return {
  extras = {
    enabled = { "lang.rust", "debug.dap" },
  },
}

Run :BlakExtras sync after enabling it, and :restart if you already started a debug session in the current session.

<leader>dc in a Rust file runs cargo build in the file’s crate, then debugs the binary it built, so breakpoints always match the source. A crate or workspace with several binaries asks which one; a failed build shows its errors and starts nothing. The program runs from Neovim’s working directory, and Rust’s LLDB formatters show String, Vec, and other standard types by value.

To pass arguments, add a configuration of your own next to Blak’s:

return {
  plugins = {
    specs = {
      {
        "mfussenegger/nvim-dap",
        opts = function(_, opts)
          local blak = opts.configurations.rust[1]
          table.insert(opts.configurations.rust, vim.tbl_extend("force", blak, {
            name = "Debug binary with arguments",
            args = function()
              return require("dap.utils").splitstr(vim.fn.input("Arguments: "))
            end,
          }))
        end,
      },
    },
  },
}

Blak does not add a Rust test adapter for test.neotest. The only standalone one, rouge8/neotest-rust, is archived and needs cargo-nextest; rustaceanvim’s adapter needs rustaceanvim, which replaces Blak’s rust-analyzer setup. Run tests with cargo test, or add an adapter yourself as shown in the neotest extra.

Disabling either extra removes the adapter after :restart; Mason keeps codelldb installed until you run :MasonUninstall codelldb.

Install and verify

:BlakExtras sync
:BlakToolsInstall
:BlakTreesitterInstall
:BlakDoctor

Open a Rust file and check :checkhealth vim.lsp for rust_analyzer.