Missing doctrine/common requirement ?

[MelvinLoos]

I might be missing something so correct me if I am wrong but I found the following issue:
serializer/src/JMS/Serializer/Handler/ArrayCollectionHandler.php contains a use statement,

use Doctrine\Common\Collections\ArrayCollection;

however the Doctrine\Common library is not included in the composer.json file requirements so this results in a class not found message.

This is for a production environment installed by composer install --no-dev, the development does not have this problem as it is apparently installed through one of the dev dependencies:

>> composer depends doctrine/common
doctrine/dbal requires doctrine/common (>=2.3.0,<2.5-dev)
doctrine/phpcr-odm requires doctrine/common (~2.4.0)

Include doctrine/common as requirement?

[goetas]

Doctrine is an optional requirement, so if you want to use ArrayCollection you have to include it by your self.

A similar case to use as example is the symfony dependency componenent. that uses the YAML dumper
https://github.com/symfony/dependency-injection/blob/master/Dumper/YamlDumper.php#L14 but the component it self is not part of requirements as is visible in https://github.com/symfony/dependency-injection/blob/master/composer.json#L18

[MelvinLoos]

I don't totally agree on the reason of use being the same in the case you provide. In the case of the symfony dependency component the YamlDumper class is purely used for development/testing (like the var_dump function) therefore justifying the dev requirement of said repository . Maybe @fabpot can even confirm this.
In the case of JMS this might be an optional component but even so it is enable by default through the builder at SerializerBuilder::addDefaultHandlers ([https://github.com/schmittjoh/serializer/blob/master/src/JMS/Serializer/SerializerBuilder.php]). And if it were optional wouldn't it be handier to add it to the "suggest" section of composer.json? Because now you will not find the missing dependency until you run composer without dev requirements.