Assistance – Am I using RustAnalyzer target correctly?

[cpolish]

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• 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).
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Description

Hi, thanks for the amazing plugin! I was drawn in in-particular as I noticed that this plugin allows you to dynamically change the Rust Analyzer target platform at runtime. I'm currently working on a project which has a lot of platform-specific compilation, so this feature seems perfect for me.

However, I've been having some trouble trying to get this to work. In particular, in a file where I have functions annotated with #[cfg(target_os = "windows")] and #[cfg(target_os = "macos")], if, when on my macOS system, I try and run RustAnalyzer target aarch64-pc-windows-msvc, Rust Analyzer will reload (since I use Fidget on my personal config to provide LSP notifications, I can see this), but unfortuantely, the highlighted/disabled regions do not change for my functions – in fact, they remain fully highlighted, almost as if semantic highlighting temporarily stops working. If I then close and reopen the same file, the highlighted regions remain the same as if the Cargo target was still macos.

I also noticed that when running checkhealth vim.lsp, that when inspecting the settings that Vim sees rust-analyzer as having, it does not appear that the target changes on here:

vim.lsp: Active Clients ~
- rust-analyzer (id: 2)
  - Version: 0.0.0 (e464ff8c75 2025-05-18)
  - Root directory: ~/Documents/Work/TechLab/scribe-bard-v1/src-tauri
  - Command: { "/opt/homebrew/bin/rust-analyzer", "--log-file", "/var/folders/l_/7b4qm11x5h96v94dv6x5y0480000gn/T/nvim.chris/nqoL4G/0-rust-analyzer.log" }
  - Settings: {
      ["rust-analyzer"] = {
        check = {
          command = "clippy",
          extraArgs = { "--no-deps" }
        },
        checkOnSave = true,
        files = {
          watcher = "server"
        }
      }
    }
  - Attached buffers: 1

which seems to maybe indicate why the highlighting for enabled/disabled cfg regions remains the same (though I don't know if the settings checkhealth vim.lsp recognises should be 100% accurate for rustaceanvim).

I can also reproduce the same behaviour when using a minimal config (as described below). Since the minimal config does not use Tree Sitter, the way I check whether it is correctly detecting disabled regions is by using the LSP hover functionality (shift-K) to see if hover docs appear for #[cfg(target_os = "windows")] vs. #[cfg(target_os = "macos")] regions of code, and by using checkhealth vim.lsp (which outputs the above).

I wanted to check with a discussion first – is there maybe something that I'm doing wrong or potentially misusing about the RustAnalyzer target command that might cause it to not work as I expect? Perhaps I could be misunderstanding what the command is supposed to be doing when I run it?

Please do let me know, any help would be much appreciated! :)

Example Code

vim.env.LAZY_STDPATH = '.repro'
load(vim.fn.system('curl -s https://raw.githubusercontent.com/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)

v0.11.1

Operating system/version

macOS 15.5 (24F74)

Output of :checkhealth rustaceanvim

# NOTE: This is the output when using the minimum reproduction above.

Checking for Lua dependencies ~
- ✅ OK optional dependency nvim-dap not installed. Needed for debugging features [mfussenegger/nvim-dap](https://github.com/mfussenegger/nvim-dap)

Checking external dependencies ~
- ✅ OK rust-analyzer: found rust-analyzer 0.0.0 (e464ff8c75 2025-05-18)
- ✅ OK Cargo: found cargo 1.87.0 (Homebrew)
- ✅ OK rustc: found rustc 1.87.0 (17067e9ac 2025-05-09) (Homebrew)

Checking config ~
- ✅ OK No errors found in config.

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

Checking for tree-sitter parser ~
- ⚠️ WARNING No tree-sitter parser for Rust detected. Required by 'Rustc unpretty' command.
- ✅ OK .vscode/settings.json loaded without errors.

# NOTE: I just realised the above mentions `.vscode/settings.json`, however, in the repository I am using, no `rust-analyzer` settings are set in this.

[mrcjkb]

Hey 👋

I can't reproduce this with the steps you've provided.
On NixOS, after running :RustAnalyzer target aarch64-pc-windows-msvc, checkhealth vim.lsp gives me:

vim.lsp: Active Clients ~
- rust-analyzer (id: 2)
  - Version: 2025-05-12
  - Root directory: ~/git/github/nvim-neorocks/lux
  - Command: { "/nix/store/sr211r4bssa5s2nqqadyhycsi6s1pr8l-rust-analyzer-2025-05-12/bin/rust-analyzer", "--log-file", "/tmp/nvim.mrcjk/nC7WPz/0-rust-analyzer.log" }
  - Settings: {
      ["rust-analyzer"] = {
        cargo = {
          loadOutDirsFromCheck = true,
          runBuildScripts = true,
          target = "aarch64-pc-windows-msvc"
        },
        check = {
          command = "clippy",
          extraArgs = { "--no-deps" }
        },
        checkOnSave = true,
        inlayHints = {
          lifetimeElisionHints = {
            enable = true,
            useParameterNames = true
          }
        },
        procMacro = {
          enable = true
        }
      }
    }
  - Attached buffers: 3

Note: If the target you are trying to set isn't supported by your toolchain, rustaceanvim will give you a Invalid target architecture provided: error message.
You can see which targets are supported with rustc --print target-list.