Buildkit treats invalid image "successfully" if corresponding digest has already been pulled

[dubo-dubon-duponey]

This is not a dagger issue, but a buildkit one.

Basically, if busybox@sha256:e2af53705b841ace3ab3a44998663d4251d33ee8a9acaf71b66df4ae01c3bbe7 has previously been retrieved and cached by buildkit, any subsequent call to
WHATEVERLALAL@sha256:e2af53705b841ace3ab3a44998663d4251d33ee8a9acaf71b66df4ae01c3bbe7 will succeed (unexpectedly).

This should be reported to buildkit eventually.

This will make one the test fail (fetch-container/nonexistent/image-with-valid-digest), which is currently disabled.

[dubo-dubon-duponey]

Reproducer:

bk: #up: [
	op.#FetchContainer & {
		ref: "busybox@sha256:e2af53705b841ace3ab3a44998663d4251d33ee8a9acaf71b66df4ae01c3bbe7"
	},
	op.#FetchContainer & {
		ref: "whatever@sha256:e2af53705b841ace3ab3a44998663d4251d33ee8a9acaf71b66df4ae01c3bbe7"
	}
]

[shykes]

@aluzzardi is this still relevant in Europa?