(Feature->Feature), or module, e.g. (Multisite->Multisite), you can see all dependencies contained in the layer/module, including any invalid dependencies. Any entries with the INVALID:... prefix are invalid and will state the reason why the dependency is invalid, as well as the source and target template path information to help you track down the offending template(s).INVALID:... documentation for the dependency that you find on a Layer or Module dependency model.metaball parameter, thus you can create your own custom error handling logic that runs after generation has completed by creating a custom completion handler.