TYPO3 Core

As topic says, once sibling issues are taken care of, the necessary API to finally migrate core caches to PSR-6 implementations will be in place. The migration then consists of:

• Implementing a PSR-6 delegating cache backend using existing cache backend infrastructure
• Make CacheManager capable of constructing these new types of cache pools, using communicators where needed
• Reduce core cache configurations to minimum and for as much as possible, rely on the shared base cache configuration
• Implement a special "generated PHP code" PSR-6 cache pool allowing saving generated raw PHP code such as Fluid templates (and which is more efficient than normal file based storage; replicating PhpFrontend + *FileBackend performance)

Once migrated, the caching framework will consist exclusively of and everything else will be deprecated:

• VariableFrontend + PhpFrontend + FrontendInterface
• PSR delegating "backend" (for compatibility, this behaves the same as existing backends and is drop-in replaceable with any backend type)
• Custom implementation cache pool which saves raw PHP code and exported plain-value arrays

When deprecation expires and it is time for removal, the following refactoring can then be done:

• Get rid of the PSR-6 delegating backend and let frontends speak directly to the PSR-6 cache pools
• Remove all cache backend classes and entire namespace
• Remove all custom cache backend exceptions