**Steps to reproduce**
* Well currently there is not possible to reproduce since this is a feature request please see below.
**Actual results**
* Currently we have to either do for example
if ( ( !defined( 'WIKIBASE_DATAMODEL_VERSION' ) || !defined( 'Diff_VERSION' ) || !defined( 'DATAVALUES_VERSION' ) )
&& file_exists( __DIR__ . '/../vendor/autoload.php' ) ) {
include_once __DIR__ . '/../vendor/autoload.php';
}
and set it either in the main php file which should be deprecated if extension.json is supported or load it through a callback in extension.json but that wont work properly.
**Expected results**
* I propose the we create something like
"vendor": "VendorAutoload.php" field in extension.json that will be loaded before anything else if set.
Currently it wont be possible to set stuff like class exists or defined in that field so it would load it from a separate file which would host the code for example like
if ( ( !defined( 'WIKIBASE_DATAMODEL_VERSION' ) || !defined( 'Diff_VERSION' ) || !defined( 'DATAVALUES_VERSION' ) )
&& file_exists( __DIR__ . '/../vendor/autoload.php' ) ) {
include_once __DIR__ . '/../vendor/autoload.php';
}
it should be loaded before anything else since we carn't use a callbackfor everything. So I suggest if that field is detected then that file should have to be loaded before anything continues.
I would consider this a blocker for Converting wikibase.