Bad HQL query in the 'colorTheme' property of XWikiPreferences in a subwiki after an upgrade from 6.1 to 6.2

• In 6.1, we did not bundle XWiki.XWikiPreferences in subwikis' XARs. As a result, XWiki used the document initializer to create the class, and set the HQL query of the property colorTheme.
• In 6.2, we have updated the HQL query of the colorTheme property to handle the new Flamingo themes.
• In 6.2, we have put XWiki.XWikiPreferences in subwikis' XARs back.
• During the upgrade, Distribution Wizard performs a merge between the preferences class previously created by the XWiki initializer and the new one bundled in the XAR.
• Problem: it does not merge the colorTheme property because DW considers that it has been manually created. The HQL query of the property stays the old one.
• Results: issue XE-1422.

Solutions:

• we do not have any solution yet about upgrading mandatory documents that are not present in a XAR, and we cannot rely on DW to upgrade them. Actually, there is an automatic upgrade that checks for the existence of a property in a class, but it does not change its settings (ie: HQL query, custom displayers, etc...)

Workaround:

• There is a new custom displayer for the colorTheme property. To avoid code duplication, it uses the HQL query of the property to display the available color themes. But we can rewrite (and duplicate) the query in the custom displayer so that it will display all the color themes. It will fix the issue but introduces technical debt.

Note:

• it should only concerns wiki upgraded from 6.1, since it is, AFAIK, the only version where subwikis' XAR did not bundle XWiki.XWikiPreferences. See: XWIKI-10772.