Use a clock interface for the time service class

[ramsey]

From @heiglandreas:¹

While you're at it... Why not use a predefined clock-interface/implememtation?

I know it's not much to implement. And weighing dependencies and less code to maintain is probably in favour of less dependencies.

See stella-maris/clock.

Footnotes

1. https://twitter.com/heiglandreas/status/1576381463771025408?s=20&t=lj0_dBx0baRQV8N_1fNpbg ↩

[drupol]

I was about to open a discussion about it and it seems that it's already done!

Definitely supporting this.

[ramsey]

I went to try to implement this and realized that ClockInterface doesn't quite fit what's needed in this library. ClockInterface only provides now(), but getting the date-time instance from a clock doesn't always mean getting the current date-time.

For example, if I change the following to adhere to the ClockInterface, then now() no longer makes sense:

identifier/src/Service/DateTime/StaticDateTimeService.php

Lines 21 to 41 in fb7a036

	/**
	* A date-time service that always returns a pre-defined date-time
	*/
	final class StaticDateTimeService implements DateTimeService
	{
	/**
	* @param DateTimeImmutable $dateTime The date-time instance this service
	* should always return
	*/
	public function __construct(private readonly DateTimeImmutable $dateTime)
	{
	}
	/**
	* Returns a pre-defined, static date-time
	*/
	public function getDateTime(): DateTimeImmutable
	{
	return $this->dateTime;
	}
	}

[drupol]

You can implement any type of clock using that new standard interface, like frozenclock.

I will make a snippet during the day.

You could also have your own clock interface, decorating the standard one.

[heiglandreas]

But isn't your DateTimeService already a Clock-implementation? Just with different naming?

DateTimeService => ClockInterface
DateTimeService::getDateTime() => ClockInterface::now()
CurrentDateTimeService => SystemClock
StaticDateTimeService => FrozenClock

Or did I miss something?

And the now does make sense as you always want the current time. In the process of your tests though you want to be "now" at a specific predictable point in time.

[ramsey]

Sounds good. What's the best way to implement a clock interface that's forward-compatible with PSR-20?

[heiglandreas]

stella-maris/clock is implemented by several implementations already and it will extend PSR-20 as soon as it is released.

As there currently isn't a release date for PSR-20 that might be your best bet currently.

If PSR- 20 gets releasee before your initial release here you can always swap out the interface. As the implementations will be PSR-20 compatible from day one that will work without issues.