Topic on Project:Support desk

When trying to upgrade to Mediawiki 1.38 from 1.36, I'm getting a fatal error:

Fatal error: Wikibase\DataModel\Entity\SerializableEntityId cannot implement Wikibase\DataModel\Entity\EntityId - it is not an interface in /var/www/vhosts/mediawiki_1_38/w/extensions/Wikibase/lib/packages/wikibase/data-model/src/Entity/SerializableEntityId.php on line 11

I have tried running composer update --no-dev multiple times, I have made sure that all extensions are included in the root composer.local.json, I have tried running git submodule update --init --recursive, but nothing seems to be helping. Arghhh.

In September 2021, EntityId became an interface, instead of an abstract class: https://github.com/wmde/WikibaseDataModel/commit/b79abc69c6d3b524a354ca395554c4dabeafcf08#diff-9864105673f0094bd8bd3b3b1b6e33088e93a96b5fc8d2297d869e1facb1a13d .

I have verified in my Wikibase source code that EntityId is in fact defined as an interface. I don't see why SerializableEntityId is tripping up on this...

I found the problem, thanks to a heads up on phabricator. I had run composer update --no-dev in each extension's folder other than in the root directory. I had to remove any vendor folders under the extension folders, and make sure composer update --no-dev was ONLY run in the root folder.