[jira] [Commented] (ISIS-2575) PanelAbstract found to be suspectious generic by the IDE because of erasure clash.

["Andi Huber (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ISIS-2575?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17300438#comment-17300438 ] 

Andi Huber commented on ISIS-2575:
----------------------------------

Very high level quality feedback. Thanks for that! Certainly going to look into it, if it can be fixed that easily.

> PanelAbstract found to be suspectious generic by the IDE because of erasure clash.
> ----------------------------------------------------------------------------------
>
>                 Key: ISIS-2575
>                 URL: https://issues.apache.org/jira/browse/ISIS-2575
>             Project: Isis
>          Issue Type: Improvement
>          Components: Isis Viewer Wicket
>    Affects Versions: 2.0.0-M3, 2.0.0-M4
>         Environment: IntelliJ IDEA 2020.3.2 (Ultimate Edition)
> Build #IU-203.7148.57, built on January 26, 2021
> Runtime version: 11.0.9.1+11-b1145.77 amd64
> VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
> Linux 5.8.0-44-generic
> GC: ParNew, ConcurrentMarkSweep
> Memory: 8083M
> Cores: 16
> Current Desktop: ubuntu:GNOME
>            Reporter: Miklós Győrfi
>            Priority: Minor
>             Fix For: 2.0.0-M5
>
>
> Due to the generic handling of Wicket and Isis, there is an annoying error message in IDE (IntelliJ (IntelliJ IDEA 2020.3.2 (Ultimate Edition) Build #IU-203.7148.57) and Eclipse as well):
> {{'setDefaultModel(IModel model)' in 'org.apache.wicket.MarkupContainer' clashes with 'setDefaultModel(IModel model)' in 'org.apache.wicket.IGenericComponent'; both methods have same erasure yet neither overrides the other}}
> It is displayed on every class which is PanelAbstract descendant. The root cause is the generic-raw-generic inheritance tree branch: PanelAbstract is a generic parametrized by IModel, and its ancestor, PanelBase is originally  a generic parametrized by the content of the IModel.  Basically PanelAbstract should be declared as 
> {code:java}
> class PanelAbstract<U, T extends IModel<U>> extends PanelBase<U>  ...
> {code}
> Of course, this is inconvenient and repetitive, but Java can't infer U from T. 
>  
> So it is fair cause to use raw type in-the-middle to change, "unbox" the parameter. But this cause a huge mess in the IDE. Two ancestors of PanelAbstract  has the same method: setDefaultModel in IGenericComponent<T, GenericPanel<T>> (which is generic, and the method is default) and MarkupContainer (which is NOT a generic) won't match any more, although their erasure won't be different: the compiler complains.
> There is a comment in PanelAbstract about this solution describing it suspectious.
> My suggestion to solve this problem:
> Simply make the PanelBase to be raw, using Panel instead of GenericPanel<T>:
> {code:java}
> public class PanelBase extends Panel implements HasCommonContext {
> {code}
>  
>  
> This simply solves the problem, and removes the generic-raw-generic ancestor tree mess (Panel and its ancestors are raw types), makes the inheritance cleaner.
> There are some places where PanelBase is used directly, but these can be solve easily as most of them are PanelBase<Void>.
>  
> Other solution is to keep the generic:
> {code:java}
> public abstract class PanelAbstract<T extends IModel<?>> 
> extends PanelBase<Object>
> {code}
> but getModel will return IModel<Object> which is not compatible to T of course, so we need another method, for example getPanelModel() which returns T. This need more refactoring, so I suggest the first.
>  
>  
> It is a minor problem, but very annoying to develop new PanelAbstract descendant, so I would be happy to see a solution.
>  
> Some links, in connection with this problem:
> https://issues.apache.org/jira/browse/WICKET-6804
> https://stackoverflow.com/questions/51931500/wicket-8-wicket-setdefaultmodel-clashes-with-setdefaultmodel
>  
>  



--
This message was sent by Atlassian Jira
(v8.3.4#803005)