datasets should not be written to disk if the policy marks the dataset as input only.
Nate Pease, a quick look at the diff against master makes me wonder if that's the wrong diff for this review. Could you please create the PRs that would make it clear what's on this ticket vs. others (and the same for DM-8016)?
Jim Bosch - sorry, I meant to create the PRs. It's done now.
the obs_base PR isn't showing up for some reason. It's this one https://github.com/lsst/obs_base/pull/7
My review complete. Everything looks fine. I was originally unconvinced that the right behavior for an input-only dataset was a silent no-op, but your test example with a input-only component of a composite helped me think of a use-case for which that probably is the right behavior (camera geometry in an Exposure).