KirbyTags: `(date: year)` does not reset cache on New Year's Day

[nilshoerrmann]

Description

When using the KirbyTag (date: year), the current year is returned automatically. If the HTML output is cached, it will not be reset on New Year's Day.

Expected behavior
When (date: year) is used on a page, the cache should expire on New Year. This can be achieved by adding the following line before returning the date:

kirby()->response()->expires('midnight first day of next year');

Your setup

Kirby Version
Kirby 5.1 and all versions before.

Additional context
It might be interesting to add an expiry attribute to the tag, to allow for custom expiries set by the author:

	/**
	 * Date
	 */
	'date' => [
		'attr' => [
			'expiry'
		],
		'html' => function (KirbyTag $tag): string {
			kirby()->response()->expires($tag->expiry ?? 'midnight first day of next year');

			if (strtolower($tag->date) === 'year') {
				return date('Y');
			}

			return date($tag->date);
		}
	],

[afbora]

I haven't tested it but I loved the solution 👍 One quick note: I would have made setting the cache expire time optional like that:

if ($tag->expiry !== null) {
  kirby()->response()->expires($tag->expiry);
}

I'm not sure if setting it here alone will work. It might be overwritten if the cache expires are set elsewhere.

[nilshoerrmann]

@afbora Making the expiry optional removes the actual fix in my eyes :D

The default setting is there to make sure that the cache is reset at all. The expiry attribute should only be used if another point in time is needed for resetting (e. g. (date: Y-m-d expiry: tomorrow)). But resetting at a given date is always a requirement, otherwise you would not need the Kirby tag in the first place and could just write the date out by hand.