Breaking: #92532 - Support for extension-in-extension installation in Extension Manager removed

See Issue #92532

Description

The installation process within the Extension Manager allowed extensions to be installed having custom dependencies to other extensions in EXT:my_extension/Initialisation/Extensions/third_party_ext.

This feature was originally introduced for the Introduction Package, which had a few more dependencies until TYPO3 v9.

As this (undocumented) feature was not used in public for any other extensions, and since Extension Manager can fetch dependencies from TER directly as well, this feature is removed.

Impact

If an extension is installed which contains other extensions as dependencies in Initialisation/Extensions/* they are now ignored on installation, and instead looked up in the remote TYPO3 Extension Repository, as with any other depending extension.

Affected Installations

TYPO3 extensions using this dependency management as “Extension-in-Extension” functionality.

Migration

Upload the proper extension into https://extensions.typo3.org and remove the folder Initialisation/Extensions from any custom extensions.