Update optional_dependencies.rst

[hbgamra]

Update optional Dependency param

[xabbuh]

What is the reason for this change? I mean why should one pass null to a setLogger() method?

[hbgamra]

You are right, but ultimately the parameter can accept null and is likely to be null

[xabbuh]

Why is that likely? I’d argue that if you don’t want to set a logger, don’t call this method. For now, I don’t see a reason why we should change the docs, but you can of course do it differently in your code if you prefer to.

[OskarStark]

Why should I call an optional method with an optional parameter? I would Justinian the setLogger() method call

[hbgamra]

You raise a valid point. Calling an optional method with an optional parameter may seem redundant and it's not good

[javiereguiluz]

This example is part of this section:

Ignoring Missing Dependencies
-----------------------------

The behavior of ignoring missing dependencies is the same as the "null" behavior
except when used within a method call, in which case the method call itself
will be removed.

[...]

So, in this example, the argument of public function setLogger(LoggerInterface $logger): void doesn't have to be nullable because, if $logger is null, the method will never be called. So, the method will never receive a null argument.

If you use this method in other parts of the app, then the argument could be nullable depending on your code. But, for the code example of this doc section, is not strictly needed. That's why I'0m closing this PR as won't fix. @hbgamra if you think I missed something, please tell me and we'll reopen this. Thanks!