Re: [xwiki-devs] [VOTE] Change the Class Fan-Out Complexity maximum value in our checkstyle configuration

Hi devs, Short version: I'd like to increase the allowed maximum value for the Class Fan-Out Complexity checkstyle rule from 20 to 25, since a bare component already uses 1 to 4 imports, and the 20 rule was set before we had components. Long version: The Class Fan-Out Complexity metric measures how many other classes are used by a class. Keeping this to a small value is a good goal, since it favors loose-coupling, small and independent classes, and makes it harder to put more than one responsibility in a single class. However, there are several problems: One is that this counts utility classes and interfaces, such as java.util.List, and a fairly complex class uses more than one such utility class; they usually come in pairs (the interface and the implementation). And more and more classes are using apache-commons utilities like StringUtils or IOUtils, which are just shortcut helper methods that could be implemented in a few lines of code, so we're trading one import for reduced code complexity, which is a good thing, even though apparently it's increasing the Fan-Out measure. Another is that a bare Initializable component implementation will import: - its component role interface - Initializable and InitializationException - Logger And since good libraries also follow the "many small classes" paradigm, barely using some of our dependencies will add a lot of imports. For example, the LucenePlugin has 25 org.apache.lucene.* imports just for initializing the server and sending search requests. While the current maximum, 20, is enough for the majority of our classes and interfaces, I've found myself often enough trying to refactor a class to get down from 23 or even 21 imports, and usually I find myself doing ugly tricks, keeping the actual code complexity the same or even worse. Best case is that I extract an extra class that just contains the non-public utility methods that were initially in the component implementation, but that class is meaningless out of the context of its parent class, so that is also a bad decision, IMHO. So, I propose to increase the Fan-Out limit to 25, while keeping the requirement that classes should be kept as small as possible.