How to properly install dependencies in symfony 3 via composer?

Question

symfony

Good afternoon!
I apologize for the question, but I just started to master symphony, I never had such problems with Yii 2.
Essence of the question, I have dependencies in composer.json, in the next pull I got a new extension that I need to install, all configs are already registered for this extension (in AppJernel.php and config.yml
) that a plug-in was not found in the AppKernel, this is of course reasonable, it does not exist yet, but why does it climb into this file at all?
How can I get rid of such problems, of course, if I remove this component from the appkernel and in cofigs, then everything will be installed, but I don’t think that such a powerful tool has such a drawback, please share your experience)