[xwiki-devs] [Proposal] Define XClass property types using components

Hi devs, Currently, the available XClass property types are hard-coded in MetaClass [1]. So in order to add a new property type you need to recompile the XWiki old core. I'd like to be able to create new property types using components so I created this branch [2] that includes the following important changes: (A) Use the value of the "classType" XML element from the XAR as a property type hint If you look at the XML export of an XClass you'll see that each property has a "classType" element whose content is the full name of the Java class used to implement that property type: <classType>com.xpn.xwiki.objects.classes.DBTreeListClass</classType> I think this is bad because: * it exposes an implementation detail * you cannot change the property type implementation without breaking backwards compatibility So I'm proposing to use the "classType" as a hint for the property type. Well, technically it will be a hint, but semantically it will specify the data type of the property value (e.g. String, Date, Number). For backwards compatibility, the existing property types will have hints that can be extracted from the value of the 'classType' (i.e. the full Java class name): String hint = StringUtils.removeEnd(StringUtils.substringAfterLast(classType, "."), "Class"); So both: <classType>com.xpn.xwiki.objects.classes.DBTreeListClass</classType> <classType>DBTreeList</classType> will point to the property type with hint "DBTreeList". Of course, when exporting an XClass with the new version of the core you'll only see the property type hint. The only issue with this approach is that XClasses exported with the new version will not work on an older version but this is acceptable IMO. (B) Add a PropertyClassProvider [3] role to retrieve an instance of a property class and to access its meta class Currently, in order to define a new property type you need to create two Java classes: * one extending PropertyMetaClass, to define the list of meta properties of the new property type (e.g. displayType, dateFormat, multiSelect, etc.) * one extending ProperyClass, to define setters and getters for the meta properties and maybe some custom display. This is the property type itself. So I added a PropertyClassProvider role that has two methods: one to get the meta class and one to get a new instance of the property type (e.g. when adding a property to an XClass). As a quick implementation I transformed all meta classes into implementations of this role. Finally, I modified MetaClass to lookup property class providers instead of hard-coding the property types. WDYT? Note that I've not added any CLIRR excludes and I tested my changes with the default, unchanged, class editor and it works fine. Thanks, Marius [1] https://github.com/xwiki/xwiki-platform/blob/xwiki-platform-4.2/xwiki-platf… [2] https://github.com/xwiki/xwiki-platform/compare/feature-xclass-property-com… [3] https://github.com/xwiki/xwiki-platform/commit/fb9fcc7313ccb16f38c2d17dd7ed…