Currently extending the configuration in Magnolia can be done the following way:
One can override parts of an inherited configuration node by using
"Misuse" of extends=override
In Magnolia 4.5 extends=override was often used to "deactivate" inheritance on subnodes.
In Magnolia 5, if used like this, the Node2BeanTransformer will provide the default implementation from the type-mapping, which may cause errors in the new UI.
Example of stkPromo component in standard templating kit:
In this example stkPromo will inherit from /modules/standard-templating-kit/dialogs/generic/master/baseTeaserInternal while adding a new field "inheritable" to the tab "tabTeaser" and overriding the field "hideTeaserImage". Overriding the field "hideTeaserImage" will result in the Node2BeanTransformer using the default ConfiguredFieldDefinition (defined in magnolia-ui-form: /META-INF/magnolia/ui-form.xml). Thus causing
RegistrationException: Could not find fieldType for definition info.magnolia.ui.form.field.definition.ConfiguredFieldDefinition
as there is no FieldBuilder available for that definition. See:
Something similar happens, when extending actions and overriding parts of them:
We should introduce another value for the extends property
to fully remove subnodes from the resulting node (after inheritance).
"Normal" use of extends should be handled as is, but simply overriding configuration nodes should not result in errors that make the UI unusable. Therefore some of the default type-mapping would have to be adjusted, e.g. in the above stkPromo example, extends=override should result in a functioning dialog: the type-mapping might be adjusted to TextFieldDefinition or ConfiguredFieldDefinition should be supplied with working defaults.