Feature: #92457 - Improved Extension Repository API

Description

In previous TYPO3 Installations, connecting to a different repository type than the "official" TER (TYPO3 Extension Repository), for downloading publicly available third-party extensions, the Extension Manager component of TYPO3 Core used a non-documented API to connect to this endpoint.

In the past, there were even mirrors available, which is not practical in the current internet world anymore.

In order to be more flexible in the future, all functionality has now been encapsulated into a single API called "Extension Remotes". These are adapters to fetch a list of extensions via the ListableRemoteInterface, or to download an extension via the ExtensionDownloaderRemoteInterface.

This way it is possible to adapt any kind of remote, where as the existing concrete implementation is now built into a configuration, rather than the database for "repositories".

It is also still possible to add new remotes, disable registered remotes or change the default remote.

Custom remote configuration can be added in the Configuration/Services.yaml of the corresponding extension.

extension.remote.myremote:
  class: 'TYPO3\CMS\Extensionmanager\Remote\TerExtensionRemote'
  arguments:
    $identifier: 'myremote'
    $options:
       remoteBase: 'https://my_own_remote/'
  tags:
    - name: 'extension.remote'
      default: true

Using default: true, "myremote" will be used as the default remote.

To disable an already registered remote, enabled: false can be set.

It is also possible to use custom remote implementations to not have to deal with t3x files anymore.

extension.remote.myremote:
  class: 'Vendor\SitePackage\Remote\MyRemote'
  arguments:
    $identifier: 'myremote'
  tags:
    - name: 'extension.remote'
      default: true

Please note that \Vendor\SitePackage\Remote\MyRemote must implement ExtensionDownloaderRemoteInterface to be registered as remote.

Furthermore setting default: true only works if the defined service implements ListableRemoteInterface.

Impact

Because of the removed mirror functionality and the encapsulation of the TER API into one concrete implementation, it is much easier to extend the Extension Manager functionality for third-party usages.

This is only relevant for non-composer-mode installations, as composer-based installations use the download functionality of composer.