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Use npm cache with Yarn Classic

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

By default, the EAS npm cache won't work with Yarn 1 (Classic), because yarn.lock files contain URLs to registries for every package and Yarn does not provide any way to override it. The issue is fixed in Yarn 2+ (Berry), but the Yarn team does not plan to backport it to Yarn v1.

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

package.json
{
  "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"
  }
}