Yarn installs a dependency's optional dependencies by default. You can use --ignore-optional to work around this.

I forget this so often that this repo now exists :|

To verify:

• Clone this repo
• yarn test
  • This will install relevant dependencies, and throw an exception if:
    • The optional dependency is not installed
    • The peer dependency is installed

Expected output:

Is the optional dependency '@goodforonefare/solo-dependency-1' installed?
    true
Is the peer dependency '@goodforonefare/solo-dependency-2' installed?
    false