If, for some reason, the package.json file is removed for a local tarball package in the project cache (Library\PackageCache), the project will open with errors, and the package will not be loaded in the project.

This issue goes away if the project is opened again or if a resolve operation is triggered after the failed resolve operation happens. When a resolve operation finishes, we remove from the project cache the packages that were resolved with errors, so next time the package is needed, it is installed again, the package is fully restored, and the problem is not present anymore.

Reproduction steps:

Create/open a project and add a local tarball
Close Unity
Locate in the file system the project. Navigate to the project cache folder Library\PackageCache.
Go to the folder corresponding to the tarball package and delete only the package.json present in the folder.
Open the project again

Expected Result:

The project is opened without errors

Actual Result:

There will be an error while opening the project stating that the package.json from the local tarball in the project cache can not be found.