Nixpkgs: yarn package pins nodes 8 and ignores node 10 installed via default.nix

[JohannesRudolph]

Issue description

Beware, new nix user here so this may be entirely my fault. Apparently, the "yarn" package gets its own nodes version and ignores the nodejs version configured in the default.nix file.

I have tried finding docs on how to control a possible "indirect" dependency but couldn't figure this out.

Steps to reproduce

I have this default.nix file

with import <nixpkgs> {};
stdenv.mkDerivation rec {
  name = "env";
  env = buildEnv { name = name; paths = buildInputs; };
  buildInputs = [
    yarn
    nodejs-10_x
  ];
}

Running yarn however for a package.json that restricts

  "engines": {
    "node": "^10.12.0"
  }

results in an error.

[nix-shell:~/dev/mc/meshfed-release/panel]$ yarn
yarn install v1.12.3
[1/5] 🔍  Validating package.json...
error [email protected]: The engine "node" is incompatible with this module. Expected version "^10.12.0". Got "8.14.1"
error Found incompatible module
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
[nix-shell:~/dev/mc/meshfed-release/panel]$ node --version
v10.12.0

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

 - system: `"x86_64-darwin"`
 - host os: `Darwin 18.2.0, macOS 10.14.1`
 - multi-user?: `no`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.1.3`
 - channels(jrudolph): `"nixpkgs-19.03pre165281.7d864c6bd63"`
 - nixpkgs: `/Users/jrudolph/.nix-defexpr/channels/nixpkgs`

[marsam]

you need to override the nodejs version used by yarn https://nixos.org/nixos/nix-pills/nixpkgs-overriding-packages.html

--- i/shell.nix
+++ w/shell.nix
@@ -3,7 +3,7 @@ stdenv.mkDerivation rec {
   name = "env";
   env = buildEnv { name = name; paths = buildInputs; };
   buildInputs = [
-    yarn
+    (yarn.override { nodejs = nodejs-10_x; })
     nodejs-10_x
   ];
 }

[JohannesRudolph]

Thanks @marsam, that did the job! Looks like there's some good stuff in nix-pills that's not immediately apparent from the main docs.

[jaredramirez]

For anyone else using nvm:
With nvm, you can't have any version of node to be installed with yarn. To solve this, you can do: (pkgs.yarn.override { nodejs = null; })