The Headless Server returns now error messages when an invalid Spring Expression was called from a fetch directive. It enables feedback whether or not an Expression is correct.

Customers who previously used the fetch directive to retrieve values directly from structs without using the SettingsAdapter or the StructAdapter might experience problems.

Previously it was possible to write a Spring Expression which refered to properties which might not even exist in a Struct. This way you could refer to values in Structs and provide default values if the property does not exist.

However this had the drawback of ignoring the difference between properties which exist, but are null and properties which do not exist. The new way enforces referencing properties and functions which actually exist on Objects and Structs.

When a non existing property or function is referenced and the Expression is called, it will result in a logged Exception and a GraphQL-Error which is passed to the client.

In order to still access values from Structs, there exist the SettingsAdapter and the StructAdapter which provide access to values in Structs and the capability to provide default values in case some property in the property path does not exist. The implementation of the TeaserOverlaySettings-Type in blueprint schema provides an example for how the Adapters could be used to access the values.

(CMS-17418)