[CAUSEWAY-2107] Allow enums to implement interfaces for choices (also fixed in "v1 maintenance")

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.17.0
• Fix Version/s: v1 maintenance, 2.0.0-M3
• Component/s: Core, Viewer Wicket
• Assignee: Daniel Keir Haywood
• Reporter: Daniel Keir Haywood
• Created: 29/Apr/19 11:57
• Updated: 19/Mar/20 10:57
• Resolved: 14/May/19 14:40

Description

The code we wanted to write was equivalent to:

    public Object act(
            final INflLeague nflLeague,
            final NflRegion nflRegion,
            final NflTeamEntity nflTeam) {
        nflPlayer.updateUsingEntity((NflLeague)nflLeague, nflRegion, nflTeam);
        return this.nflPlayer;
    }

    public List<? extends INflLeague> choices0Act() {
        return Arrays.asList(NflLeague.values());
    }
    ...

where NflLeague is an enum that implements INflLeague :

public interface INflLeague {
    String getName();
}

and

public enum NflLeague implements INflLeague {
    AFC,
    NFC;

    @Override
    public String getName() {
        return name();
    }
}

There are two issues:

• first, in the metamodel we don't introspect enums to recognise that a list of NflLeague enum instances can be returned in the choices method returning List<INflLeague>

• second, in the Wicket viewer the selection of the choicesPanel is based on the type, and if an interface is used then it guesses a referencePanel rather than ValueSelect2Panel that is normally used for enums. The marshalling logic for ReferencePanel assumes entities, and fails when handed a bunch of scalar enums.