Use npm cache with Yarn 1 (Classic)

Learn how to use npm cache by overriding the registry in Yarn 1 (Classic).

By default, the EAS npm cache won't work with Yarn 1 (Classic) because yarn.lock files contain URLs to registries for every library. Yarn 1 does not provide any way to override it and Yarn team does not plan to support it in Yarn 1. However, this issue is fixed in Yarn 2+.

If you want to take advantage of the npm cache with Yarn 1, add the eas-build-pre-install npm hook in package.json to override the registry in the yarn.lock:

{
  "scripts": {
    "eas-build-pre-install": "bash -c \"[ ! -z \\\"$EAS_BUILD_NPM_CACHE_URL\\\" ] && sed -i -e \\\"s#https://registry.yarnpkg.com#$EAS_BUILD_NPM_CACHE_URL#g\\\" yarn.lock\" || true"
  }
}