Nixos: configure R.nvim for read-only plugin directories

[melhindi]

I am using R.nvim on NixOS through a Nix-managed Neovim setup, specifically nixcats.
In this setup, plugins are installed into the Nix store, which is immutable/read-only.
When opening an .R file, R.nvim tries to build runtime artifacts inside its own plugin checkout. Since the checkout is located under /nix/store, this fails with a read-only filesystem error.

  Error making rnvimserver [2].
  stdout:
  gcc -pthread -O2 -Wall complete.c resolve.c hover.c definition.c signature.c rhelp.c chunk.c roxygen.c data_structures.c logging.c
  rnvimserver.c obbr.c tcp.c utilities.c ../nvimcom/src/common.c -o rnvimserver

  stderr:
  /nix/store/...-binutils-2.46/bin/ld.bfd: cannot open output file rnvimserver: Read-only file system
  collect2: error: ld returned 1 exit status
  make: *** [Makefile:17: rnvimserver] Error 1

I also see related errors when R.nvim tries to install/build nvimcom from the plugin directory:

  Why build nvimcom: Nvimcom not installed
  Warning in dir.create(path, showWarnings = TRUE, recursive = TRUE, ...) :
    cannot create dir 'nvimcom/man', reason 'Permission denied'
  Error in mydir.create(name) : failed to create directory ‘nvimcom/man’

Environment

• OS: NixOS
• Neovim setup: nixcats
• Plugin installation model: plugins are stored in /nix/store
• R.nvim source path: read-only Nix store path
• R and build tools are available through Nix

Request/Issue

Would it be possible for R.nvim to support a separate writable build/state directory, independent of the immutable plugin source directory?
For example, something like:

  require("r").setup({
    rnvim_home = "/nix/store/.../R.nvim",      -- immutable plugin source
    build_dir = "~/.cache/R.nvim/build",      -- writable generated files
    nvimcom_lib = "~/.local/share/R/library", -- optional/user-controlled
  })

From looking at the code, config.rnvim_home is derived from the loaded plugin path and is then used for both reading source files and writing build artifacts.
At the moment, R.nvim appears to treat the plugin source directory (rnvim_home) as both the immutable source root and the writable build/state root.
Splitting these would make packaging much cleaner.

Alternatively, is there already a supported way to configure R.nvim for read-only plugin directories that I missed?

Current workaround

The workaround I am using is to copy the R.nvim checkout from the Nix store into a writable cache directory and prepend that copy to Neovim’s runtimepath. Conceptually:

  r_root="$XDG_CACHE_HOME/nvim-bootstrap/r.nvim"
  cp -a "$nix_store_rnvim_source/." "$r_root/"
  chmod -R u+rwX "$r_root"
  nvim --cmd "set runtimepath^=$r_root"

This works because R.nvim then sees config.rnvim_home as the writable cache copy rather than the immutable Nix store path.

Related Issue(s)

This is related to #229, but I believe it is a more specific remaining issue.
#229 discusses NixOS support, runtime dependencies, and packaging nvimcom. In my setup I can provide gcc, make, tar, treesitter, and even build nvimcom through Nix. However, R.nvim still tries to build rnvimserver and other generated artifacts inside config.rnvim_home, which points to the plugin checkout under /nix/store.
Because /nix/store is read-only, this fails even when all dependencies are available.

[PMassicotte]

Hi there, and thank you for your message. Just to let you know, I am also using nix. I will take time to answer your question later today when I am back at the computer.

[melhindi]

Thanks, if you need any more details about my specific setup, please let me know.

[PMassicotte]

Hi there. Are you using flake by chance?

In my workflow, the flake.nix file (see below) includes nvimcom as part of each project's Nix development environment rather than installing it globally on my system. Each R project that uses this template gets its own reproducible environment. In practice, nvimcom is built only if necessary, if an identical build already exists in the Nix store, it is reused instead of being rebuilt.

https://github.com/PMassicotte/nix-templates/blob/main/templates/r-project/flake.nix

Additionaly, the completion directory is unique for each project and is therefore not rebuilt everytime I enter in the shell. In my r.lua I have this:

compldir = vim.fn.stdpath("cache") .. "/R.nvim/" .. vim.fn.sha256(vim.fn.getcwd()),

Is this something like that you are looking for?