pub fn non_empty<T>(items: Vec<T>) -> Option<Vec<T>>Expand description
The Option sibling of require_non_empty: None for an empty list,
Some(items) otherwise.
This is the one home for the “an empty list means absent” rule, wherever a
list is being placed into an Option-shaped slot (an optional response
content, an optional message) rather than validated. The same whole-list
rule applies: never decide emptiness per item.