Current and idealised behaviour with respect to category contents, when a category is deleted...

zone:
CURRENT BEHAVIOUR:
deletes pages within
does not allow deletion of welcome zone
IDEAL BEHAVIOUR:
asks whether to delete, or where to reassign to
does not allow deletion of welcome zone

news category:
CURRENT BEHAVIOUR:
reassigns to lowest ID category
does not allow deletion of final category
IDEAL BEHAVIOUR:
asks whether to delete, or where to reassign to
if the final category no choice can be given so UI gives a clear click-through warning that all entries will be deleted

gallery:
CURRENT BEHAVIOUR:
deletes images and videos within
reassigns subgalleries to parent gallery
does not allow deletion of root gallery
IDEAL BEHAVIOUR:
asks whether to delete, or where to reassign to; default to move to parent gallery
does not allow deletion of root gallery

download category
CURRENT BEHAVIOUR:
reassigns downloads to parent category
reassigns subcategories to parent category
does not allow deletion of root category
IDEAL BEHAVIOUR:
asks whether to delete, or where to reassign to; default to move to parent category
does not allow deletion of root category

forum grouping:
CURRENT BEHAVIOUR:
asks where to reassign to
does not allow deletion of final forum grouping
IDEAL BEHAVIOUR:
(no change)

forum:
CURRENT BEHAVIOUR:
asks whether to delete, or where to reassign to
does not allow deletion of root forum
IDEAL BEHAVIOUR:
asks whether to delete, or where to reassign to; default to move to parent forum
does not allow deletion of root forum

catalogue category:
CURRENT BEHAVIOUR:
asks whether to delete; if not:
if in a tree catalogue:
reassigns entries to parent category
reassigns subcategories to parent category
does not allow deletion of root category
if not in tree catalogue:
deletes entries
IDEAL BEHAVIOUR:
asks whether to delete; if not:
if in a tree catalogue:
asks whether to delete, or where to reassign to; default to move to parent category
does not allow deletion of root category
if not in tree catalogue:
asks whether to delete, or where to reassign to
if the final category no choice can be given so UI gives a clear click-through warning that all entries will be deleted

catalogue:
CURRENT BEHAVIOUR:
deletes all categories and entries (necessarily so, not logical to move to another catalogue)
IDEAL BEHAVIOUR:
(no change)


When fixed, this functionality expectation should be generalised and added to the Code Book, and referenced in our standards checklist.

Note also we have these language strings...

DESCRIPTION_DELETE=Tick (check) this if this is to be deleted. This is immediate and irreversible.
DESCRIPTION_DELETE_LOSE_CONTENTS=Tick (check) this if this is to be deleted. This is immediate and irreversible. The contents of this category will also be deleted.
DESCRIPTION_DELETE_PARENT_CONTENTS=Tick (check) this if this is to be deleted. This is immediate and irreversible. The contents of this category will be moved to the parent category.

They should be used/adjusted to be completely accurate.

Also note how galleries currently has an option to leave files on-disk. Probably we should just remove that, as the era of people being expected to mess around with on-disk files to this extent is rather outdated. I'd rather it all be consistent.

Also see the issue reference I'm adding in sources/crud_module.php, relating to the description of the deletion checkbox.

Attached is a patch I wrote to allow configuring (via hidden option) the target news category for news to be moved to when said news' category is deleted.
I don't like how piecemeal this is, so I don't plan to merge it. It should be an option with the delete fields on the edit form.