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https://issues.apache.org/jira/browse/WICKET-6877?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Tzvetanov Grigorov resolved WICKET-6877.
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Fix Version/s: 8.13.0
9.4.0
Resolution: Fixed
> Removing component's MetaData during detach phase from within a Behavior
> causes issue
> -------------------------------------------------------------------------------------
>
> Key: WICKET-6877
> URL: https://issues.apache.org/jira/browse/WICKET-6877
> Project: Wicket
> Issue Type: Bug
> Affects Versions: 9.3.0, 8.12.0
> Reporter: Daniel Radünz
> Assignee: Martin Tzvetanov Grigorov
> Priority: Minor
> Fix For: 9.4.0, 8.13.0
>
> Attachments: quickstart.zip
>
>
> When removing a component's MetaData entry from within a Behavior's
> {{detach(Component component)}} method, Wicket can run into issues due to a
> loop index being out of sync with the array it is iterating over.
> The attached quickstart shows the problem in the log when the HomePage is
> opened.
> Explanation:
> The included VisibilityBehavior class adds a MetaData entry to the component
> it is attached to. Upon detaching the Behavior this MetaData entry is set to
> null again. Setting a MetaData entry to null removes it from the component's
> data array, moving all elements following it further up in the array.
> State captured in {{org.apache.wicket.Behaviors.detach(Component)}}:
> Right before detaching the Behavior:
> Loop index "i" = 2
> Content of the component's "data" array:
> - [0] the component's Model
> - [1] the MetaDataEntry belonging to the described Behavior
> - [2] the Behavior itself
> - [3] an AttributeModifier with a StringResourceModel
> Start of next iteration after the Behavior was detached
> Loop index "i" = 3
> Content of the component's "data" array:
> - [0] the component's Model
> - [1] the Behavior itself
> - [2] an AttributeModifier with a StringResourceModel
> Result:
> The AttributeModifier is skipped and doesn't get detached, resulting in the
> NotDetachedModelChecker reporting a not detached model in the
> AttributeModifier, when the HomePage gets opened.
> This might be fixable with the suggested separation of Models, Behaviors and
> MetaData from WICKET-6774. Alternatively Wicket could maybe raise an
> exception or log a warning if the size of the data field changed during
> detaching.
> The problem was first discovered in 8.10.0 and reproduced with 9.3.0 in the
> quickstart.
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