Open 2.0 - PHP 7.2, change namespace

[Majkl578]

• Open 2.0
• Require PHP 7.2
• Change namespace to Doctrine\Annotations

I'd like to make this PR a starting point for upcoming Annotations 2.0, gradually reviving #75. 🎉
It won't be as easy as it may look, it is not up to date with master, also is a bit older - built back in pre-7.1 era. Thus I would like to split it into smaller chunks - here and in next PRs.

1.7/1.8 would be the last 1.x release shipping compatiiblity layer for 2.0 (similar to ORM 2.7 for 3.0).

[Ocramius]

I feel like this will be a massive BC break. In BetterReflection, we had introduced a shim for this: https://github.com/Roave/BetterReflection/blob/44ef19dc4544a0673a00a080a2d3a1c60d5ce42b/namespace-bc-aliases.php

[Majkl578]

See:

1.7/1.8 would be the last 1.x release shipping compatiiblity layer for 2.0

It will be a BC break, on the other hand this is new major after 5+ years so changes are to be expected, this will not be the only BC issue. Also we want to get rid of the "Common" thing, right? 😉

Either way I am not sure whether the polyfill should go only to 1.x or 2.x too. There is plenty of time to discuss that and do properly before release.

[lcobucci]

PHPUnit's strategy wen't well IMO... namespaces got added in 6.x and compatibility layer added in 5.x.

[lcobucci]

My only concern is if we change the public API so much that the class aliasing might not be that helpful.

[Majkl578]

if we change the public API so much that the class aliasing might not be that helpful

That's true and needs to be considered, but let's keep that for discussion in specific PRs. Nothing apart namespaces is changed here. 😊

[guilhermeblanco]

@Ocramius We've spoken about this before (re: BC on namespace change) back at True North 2016 and we agreed to remove Common. =P

The motivation is that Annotations is a widely spread enough that even though makes it harder to make BC breaks, it's also a project that lives outside of Doctrine\Common umbrella. We originally defined the Common slot as support tools for ORM, but clearly it went further than we imagined. It's time to drop Common namespace.

[stof]

I agree about removing the Common part of the namespace, but only if you provide a BC layer to allow for projects to support both 1.x and 2.x in their code requiring a Reader.
Due to 2.0 supporting only PHP 7.2+, switching to doctrine/annotations 2.0 only for Symfony is not an option (as Symfony 4 supports 7.1+). This means we need to be able to support both 1.x and 2.x in our codebase