The libraries listed here are the only ones we officially depend on. Anything
else is either provided only for development purposes or an implicit dependency
that may be removed in the future, if it is properly decoupled from the packages
depending on it.

doctrine/common
doctrine/annotations
easyrdf/easyrdf
egulias/email-validator
fabpot/goutte
guzzlehttp/guzzle
masterminds/html5
stack/builder
symfony/class-loader
symfony/console
symfony/dependency-injection
symfony/event-dispatcher
symfony/http-foundation
symfony/http-kernel
symfony/routing
symfony/serializer
symfony/validator
symfony/process
symfony/yaml
symfony-cmf/routing
symfony/psr-http-message-bridge
twig/twig
zendframework/zend-diactoros
zendframework/zend-feed

If you are writing code that depends on a library not listed here, you should
add it explicitly as a dependency yourself in your own "composer.json" file.