[jira] [Updated] (WICKET-5772) LoadableDetachableModel caches null value if load() fails, bug in getObject() {attached = true;}

["Sven Meier (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/WICKET-5772?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sven Meier updated WICKET-5772:
-------------------------------
    Assignee: Sven Meier

The fix is trivial indeed.

@devs: any objections against this change on 6.x? Although unlikely, even such a small change could break existing applications.

> LoadableDetachableModel caches null value if load() fails, bug in getObject() {attached = true;}
> ------------------------------------------------------------------------------------------------
>
>                 Key: WICKET-5772
>                 URL: https://issues.apache.org/jira/browse/WICKET-5772
>             Project: Wicket
>          Issue Type: Bug
>          Components: wicket
>    Affects Versions: 1.4.23, 6.18.0, 7.0.0-M4
>            Reporter: Martin Makundi
>            Assignee: Sven Meier
>              Labels: easyfix, easytest, patch
>   Original Estimate: 10m
>  Remaining Estimate: 10m
>
> If you have a LoadableDetachableModel whose load() operation fails at an instance, the LoadableDetachableModel will cache null value because 
> getObject() method sets attached = true; before load() invocation has returned.
> This results in methods trusting LoadableDetachableModel using the null value for their operations which is logically incorrect as null might not be a legal value at all. Such behavior would result in unexpected difficult-to-debug behavior in depending components.
> Easy fix:
> Move:
> attached = true;
> after line:
> transientModelObject = load();
> Test case:
> /**
>    * LoadableDetachableModel must not return null as an attached value if load()
>    * fails.
>    */
>   public void testWhenLoadFails() {
>     final LoadableDetachableModel<Void> loadableDetachableModel = new LoadableDetachableModel<Void>() {
>       /**
>        * @see org.apache.wicket.model.LoadableDetachableModel#load()
>        */
>       @Override
>       protected Void load() {
>         throw new UnsupportedOperationException("Let's assume this fails for some reason.");
>       }
>     };
>     try {
>       loadableDetachableModel.getObject();
>       fail(UnsupportedOperationException.class + " expected.");
>     } catch (final UnsupportedOperationException e) {
>       LoggerFactory.getLogger(LoadableDetachableModel.class).debug("Expected behavior due to " + UnsupportedOperationException.class);
>     }
>     try {
>       assertNotSame(LoadableDetachableModel.class + " should not return null if it's load() has failed\n", null,
>           loadableDetachableModel.getObject());
>     } catch (final UnsupportedOperationException e) {
>       LoggerFactory.getLogger(LoadableDetachableModel.class).debug("Expected behavior due to " + UnsupportedOperationException.class);
>     }
>   }



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