I’m sorry in advance if this is a basic question, but I can’t figure out how to write a nix flake that outputs my Rust library as WASM.
I started with nix flake init --template "github:DeterminateSystems/zero-to-nix#rust-pkg"
from this guide (flake.nix pasted below). But I don’t know how to target WASM with buildRustPackage
, along the lines of cargo build --target=wasm32-unknown-unknown
.
After searching about online, I found that there was a package in nixpkgs called rustc-wasm32
, which then got merged with rustc
, so I presume the rust compiler I have supports targeting wasm32-unknown-unknown. I think I need to do something like cross-compilation, but I’m not sure.
If there is something else I should be using instead of buildRustPackage, I’d also be interested to know about that. Thank you!
flake.nix
{
description = "Rust example flake for Zero to Nix";
inputs = {
nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.2305.491812.tar.gz";
# Provides helpers for Rust toolchains
rust-overlay.url = "github:oxalica/rust-overlay";
};
outputs = { self, nixpkgs, rust-overlay }:
let
# Systems supported
allSystems = [
"x86_64-linux" # 64-bit Intel/AMD Linux
"aarch64-linux" # 64-bit ARM Linux
"x86_64-darwin" # 64-bit Intel macOS
"aarch64-darwin" # 64-bit ARM macOS
];
# Helper to provide system-specific attributes
forAllSystems = f: nixpkgs.lib.genAttrs allSystems (system: f {
pkgs = import nixpkgs {
inherit system;
overlays = [
# Provides Nixpkgs with a rust-bin attribute for building Rust toolchains
rust-overlay.overlays.default
# Uses the rust-bin attribute to select a Rust toolchain
self.overlays.default
];
};
});
in
{
overlays.default = final: prev: {
# The Rust toolchain used for the package build
rustToolchain = final.rust-bin.stable.latest.default;
};
packages = forAllSystems ({ pkgs }: {
default =
let
rustPlatform = pkgs.makeRustPlatform {
cargo = pkgs.rustToolchain;
rustc = pkgs.rustToolchain;
};
in
rustPlatform.buildRustPackage {
name = "zero-to-nix-rust";
src = ./.;
cargoLock = {
lockFile = ./Cargo.lock;
};
};
});
};
}