nix-yarn-devshell

.envrc

use flake

NODE_DIR="${PWD}/.direnv/node"
NODE_MODULES_DIR="${PWD}/node_modules"

export NODE_OPTIONS="--max_old_space_size=65536"
export NODE_PATH="${NODE_DIR}:${NODE_MODULES_DIR}"
export NPM_CONFIG_PREFIX="${NODE_DIR}"
export PATH="${NODE_DIR}/bin:${NODE_MODULES_DIR}/.bin:${PATH}"

NODE_INSTALL_HASH=`cat flake.lock yarn.lock | md5sum | cut -f 1 -d " "`
NODE_INSTALL_MARKER="${PWD}/.direnv/node-install"

if [[ ! -e "${NODE_INSTALL_MARKER}" || ( `cat ${NODE_INSTALL_MARKER}` != ${NODE_INSTALL_HASH} ) ]]; then
    ( yarn install )
    echo "${NODE_INSTALL_HASH}" > "${NODE_INSTALL_MARKER}"
fi

flake.nix

{
  description = "yarn development shell";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.11";
  };

  outputs = { self, nixpkgs }:
    let
      system = "x86_64-linux";
      pkgs = (import nixpkgs { inherit system; }).pkgs;
    in
    {
      devShell.${system} = pkgs.mkShell
        {
          nativeBuildInputs = with pkgs; [
            nodejs
            yarn
          ];
        };
    };
}