WP Importer should warn if WXR format is newer than it nows about

[lloydbudd]

WP Importer should warn and recommend upgrade if WXR format is newer than it is aware of.

Background

I noticed that the WP 3.1 export (deployed to WordPress.com) didn't assign categories if imported into 3.0.

Worked if importing using the new importer though, right?

Attached patches for two different approaches:

• 15634.warn-on-wxr-version.diff will hardcode a maximum supported version into the importer plugin. A warning is then displayed if a file is uploaded which has a greater version specified in the ​wp:wxr_version tag.

• 15634.warn-on-update.diff will display a warning if there is an update available for the WordPress importer. This works on the assumption that if the export file format is bumped then a new plugin will also be pushed to support the extra features.

It may also be possible to block operation instead of just displaying a warning, but this seems rather extreme. It could also be the case that the export format version number gets bumped but old importers are still compatible (don't know of a such a scenario off the top of my head), in this case I think the warn-on-update might be better.

Attached a patch to combine both approaches and also what is seen if both triggers are set off. The 'warn-on-update' note shows on every screen for the importer, the 'warn-on-wxr-version' will only show on the screen immediately after uploading a WXR file (the assign authors screen).

​http://plugins.trac.wordpress.org/changeset/344748/wordpress-importer

Only some minor tweaks to the last patch.