TYPO3 Core

The deprecation log has been disabled by default with issue #22613 and committed in r7616.
However, by disabling the deprecation log by default there's no chance for regular users to know when extensions are using deprecated APIs. When these APIs are going to be removed eventually with a later release, these users may experience crashes and fatal errors which could have been avoided if they had seen the deprecation log messages. This is bad in regards of user experience.

The deprecation log was created to allow for cleaning up and eventually removing old APIs and to still stick with backwards compatibility by letting users and developers know when they are using APIs that are subject to removal. Thus when not indicating use of these APIs to users and developers, disabling the deprecation log is like throwing over board our responsibility for backwards compatibility we have been so proud of the last years.

It is true however, that the deprecation log can grow to quite some size. Therefor a new status report entry will be added by the attached patch to let the user know whether the deprecation log is enabled, whether certain file sizes are reached, and what the current log file's size is.

Depending on the size of the log file the status will be OK for disabled deprecation log, NOTICE for enabled deprecation log, WARNING for 10MB+, and ERROR for 100MB+

(issue imported from #M14729)