Rust wasm example development environment

flake.nix

{
  inputs = {
    nixpkgs.url = github:nixos/nixpkgs/nixos-unstable;
    flake-utils.url = github:numtide/flake-utils;
    rust-overlay.url = github:oxalica/rust-overlay;
  };

  outputs = { nixpkgs, flake-utils, rust-overlay, ... }:
    flake-utils.lib.eachSystem ["x86_64-linux"] (system: let
      pkgs = import nixpkgs {
        inherit system;
        overlays = [ rust-overlay.overlay ];
      };
    in {
      devShell = pkgs.mkShell {
        nativeBuildInputs = with pkgs; [
          (rust-bin.stable.latest.rust.override {
            targets = [ "wasm32-unknown-unknown" ];
          })
          wasm-pack
          wasm-bindgen-cli
        ];
      };
    }
  );
}

Pre-aggregated package rust is not encouraged for stable channel since it contains almost all and uncertain components.
Consider use default profile like rust-bin.stable.latest.default and override it with extensions you need.

rust-bin.stable.latest.rust.override
   ↓
rust-bin.stable.latest.default.override