See #21483 for an example of a user providing an image name that causes a failure in the CNB builder that is difficult to diagnose (upper-case characters in the image name):
[INFO] > Running creator
[INFO] [creator] ERROR: failed to all tags must have the same registry as the exported image: could not parse reference: docker.io/library/SchedulePolling:1.2
If we better understood the rules for an image reference, Boot could do some validation of the image name before invoking the builder to give a better user experience. For comparison, the pack CLI gives a more concise error message, although still missing the details of what isn't acceptable about the image name:
$ pack build docker.io/library/DemoProject:1.0 --builder gcr.io/paketo-buildpacks/builder:base-platform-api-0.3 --path build/libs/demo-0.0.1-SNAPSHOT.jar
ERROR: invalid image name 'docker.io/library/DemoProject:1.0': could not parse reference: docker.io/library/DemoProject:1.0
Comment From: scottfrederick
For reference, the Google go-containerregistry library contains some rules for elements of the image name: