I'm helping out with MDL-81376 which is a fairly typical export / import features. It exports some table of data using the dataformat api for free via tablelib, and then accepts an upload of a csv file.

Technically this is a slight mismatch - in theory the site admin could turn off the csv dataformat plugin so you would be downloading in say json, and then accepting an upload in csv. I think in practice it's not a big deal, but the proper solution would:

• Allow each dataformat plugin to declare if it supports import
• Have a helper function which takes an arbitrary uploaded file, infers its type, hands it off to the right dataformat and gets back a format agnostic list of records
• Possibly we could also add a custom formslib element of a 'dataformatfileupload' which handles everything and the form handler just gets nice data without knowing how it got it.
• When exporting have an optional flag in code which filters the exports to only those which can be imported, or at least give a clear indication in the download widget that only some would be supported for import