Concept: Utils\DateTime deprecation & replacement

[Majkl578]

Hi,

this is an attempt to phase out Nette\Utils\DateTime and replace it by a new helper class.
The current DateTime makes date & time manipulation easier since it enhances \DateTime, yet it has some major flaws: mutability and inheritance.

Why should we want the new helper class?

• current DateTime contains some useful methods to ease manipulation with DateTime instance, these are moved to this new class;
• supports both mutable \DateTime and immutable \DateTimeImmutable variants, through \DateTimeInterface;
• inheritance-free, does not extend mutable \DateTime;
• does not provide magical __toString (which by the way drops the time zone information).

This PR is a draft, not a final proposal yet. It consists of new tests for existing DateTIme class as well as the actual replacement with tests as well.

I'd like to hear some feedback -- whether is it really what we want (I hope so) and what & how could be eventually changed.

(This depends on #79 which bumps composer.json & Travis versions. Hence Travis fails.)

[pavelkouril]

I definitely like the idea. 👍

[fprochazka]

Good job 👍

[dg]

createMutable() vs createImmutable() makes users think…

[JanTvrdik]

👍 For immutable only. The only good use-case for mutable DateTime is compatibility with old libraries which accepts DateTime only. Unfortunately there is no easy way in PHP core to convert DateTimeImmutable to DateTime.

[Majkl578]

createMutable() vs createImmutable() makes users think…

Agreed, maybe it could be create() vs. createMutable() or something. But I'd like to keep both for the reasons below.

The only good use-case for mutable DateTime is compatibility with old libraries which accepts DateTime only.

Exactly. And I think that is very good reason for supporting it. As an example, whole Doctrine stack still does not natively support DateTimeImmutable/DateTimeInterface (or probably any other library following semver until they bump major version).

Unfortunately there is no easy way in PHP core to convert DateTimeImmutable to DateTime.

Actually, I really thought it was in (I used it in this PR, didn't even realize), but it was reverted afterwards, because Derick was against it. :( php/php-src#1145
This is imho yet another reason to have createMutable, which could handle this stupid boilerplate internally.

[Majkl578]

What to do with this? Still doable for 3.0 where DateTime with inheritance sadly still exists, or should I just close it?