For whatever reason, the default view of a new folder is set to a ListView matching all jobs. It would be more appropriate to use an actual AllView, like Jenkins root does; the user can always add other views if they need them.
The ListView upgrade for an old existing folder (prior to folders being a ViewGroup) also seems to be unreliable; does not even log reflection failures if setting the regex fails.
On a related note, currently a newly created folder shows in its "All" view a hint to use configure to add some existing jobs (and as of
JENKINS-9330 also a hint to use newJob to create a new job). This makes no sense since there are no jobs in the folder yet. (Would be nice to have an extension point so that cloudbees-folders-plus could add a link to use "Move" from an existing job to physically move it into this folder.)
Not possible when using a ListView since we can only override noJob.jelly for a custom view type. AllView/noJob.jelly is not much better in this case.
Better would be to define a custom View type for the default view of a folder, either AllView or a subclass.
For compatibility, if old metadata actually defined nontrivial columns and/or filters we would perhaps want to create an additional "Custom" ListView.