[GROOVY-11146] Support flattening of Optionals in flatten/flattenMany

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.0.0-alpha-1
• Assignee: Paul King
• Reporter: Paul King
• Created: 03/Aug/23 02:23
• Updated: 23/Aug/23 09:11
• Resolved: 07/Aug/23 02:39

Description

The functional idiom of map/collect then flatten is so common that we normally have a shorthand for combining them: flatMap, bind, collectMany.

We have that for streams (piggybacking on Java) and collections but not optionals.

var items = ["1", "2", "foo", "3", "bar"]

var toInt1 = s -> s.number ? Stream.of(s.toInteger()) : Stream.empty()
println items.stream().flatMap(toInt1).toList()

var toInt2 = s -> s.number ? [s.toInteger()] : []
println items.collectMany(toInt2)

var toInt3 = s -> s.number ? Optional.of(s.toInteger()) : Optional.empty()
println items.collect(toInt3).flatten{ it -> it.orElse([]) }
println items.collect(toInt3).findResults{ it -> it.orElse(null) }
println items.collect(toInt3).grep()*.get()

This issue will explore options for adding that.

Issue Links

• links to: GitHub Pull Request #1926