using rustToolchain variable for creating workspace

[JohnCarterGonzalez]

In the example docs for hello-world the rust workspace is built using:

# the flake.nix file is spliced here for brevity...
# create the workspace & dependencies package set
rustPkgs = pkgs.rustBuilder.makePackageSet {
  rustVersion = "1.75.0";
  packageFun = import ./Cargo.nix;
};
# rest of flake...

I usually create my development environments through a single rustToolchain file like so:

# again the flake is spliced for brevity...
# 👇 note that it refers to the path ./rust-toolchain.toml
rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
in
with pkgs;
{
  devShells.default = mkShell {
    buildInputs = [
     rustToolchain
    ];
};
# rest of flake.nix....

Not saying this is the best approach, I am just curious if something like this is possible in the build dev-env section for cargo2nix? Thanks for your time.

[JohnCarterGonzalez]

an example of what I mean would be like:

rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
rustPkgs = pkgs.rustBuilder.makePackageSet {
  rustupToolchain = rustupToolchain; # not sure what the declaring variable would be here
  packageFun = import ./Cargo.nix;
  # ...

and the rust-toolchain.toml would look like:

[toolchain]
channel = "1.75"
profile = "minimal"
components = [ "rustfmt", "clippy" ]
targets = [ "x86_64-apple-darwin", "aarch64-apple-darwin", "wasm32-wasi" ]

the dev-env would be built using the toml file and the cargo2nix would build the bin rust pkg. I hope the example makes sense!

[psionic-k]

The workspace shell attribute is an augmentation of vanila mkShell. You can put arbitrary things in as needed.

IIRC NIx has some toml reading tools. If you translate that to a toolchain expression, you can read a rust-toolchain.toml like in your example.