Breaking: #78581 - Hook getFlexFormDSClass no longer called 

See forge#78581

Description 

With the deprecation of BackendUtility::getFlexFormDS() the hook getFlexFormDSClass is no longer called and there is no substitution available.

Impact 

The hook is no longer called and flex form field manipulation by extensions does not happen anymore.

Affected Installations 

Extensions that extension flex form data structure definitions and use the hook getFlexFormDSClass for that purpose.

Migration 

Method BackendUtility::getFlexFormDS() has been split into the methods FlexFormTools->getDataStructureIdentifier() and FlexFormTools->parseDataStructureByIdentifier().

Those two new methods now provide four hooks to allow manipulation of the flex form data structure location and parsing. The methods and hooks are documented well, read their description for a deeper insight on which combination is the correct one for a specific extension need.

The new hooks are very powerful and must be used with special care to be as future proof as possible.

Since the old hook is used by some widespread extensions, the core team prepared a transition for some of them beforehand:

  • EXT:news: The extension used the old hook to only remove a couple of fields from the flex form definition. This has been moved over to a "FormEngine" data provider: news
  • EXT:flux: Flux implements a completely own way of locating and pointing to the flex form data structure that is needed in a specific context. The default core resolving does not work here. Flux now implements the hooks getDataStructureIdentifierPreProcess and parseDataStructureByIdentifierPreProcess to specify an own "identifier" syntax and to resolve that syntax to a data structure later: flux
  • EXT:gridelements: Similar to flux, gridelements has an own logic to choose which specific data structure should be used. However, the data structures are located in database row fields, so the "record" syntax of the core can be re-used to refer to those. gridelements uses the hook getDataStructureIdentifierPreProcess together with a small implementation in parseDataStructureByIdentifierPreProcess for a fallback scenario: gridelements
  • EXT:powermail: Powermail allows extending and changing existing flex form data structure definition depending on page TS. To do that, it now implements hook getDataStructureIdentifierPostProcess to add the needed pid to the existing identifier, and then implements hook parseDataStructureByIdentifierPostProcess to manipulate the resolved data structure: powermail