2.x Remove Attachment::$caption property in favor of Attachment::caption() method

[gchtr]

Ticket: #2610

• Fixes Caption on thumbnails is empty (2.x) #2607

Issue

This pull request iterates on the work by @xavivars in #2610 (thanks, @xavivars). For 2.x, we missed that the caption of an attachment is set while initializing it. See this excerpt from 1.x:

timber/lib/Image.php

Lines 215 to 217 in 8d9bff2

	if ( isset($basic->post_excerpt) ) {
	$this->caption = $basic->post_excerpt;
	}

Solution

This pull request:

• Adds a test to confirm the bug in Caption on thumbnails is empty (2.x) #2607.
• Removes the Attachment::$caption property and instead adds an Attachment::caption() method. I think this is the approach we choose more and more: Using methods instead of countless properties we have to initialize.
• Updates the Upgrade guide.
• Adds the wp_get_attachment_caption filter, which is used in the equivalent WordPress core function wp_get_attachment_caption().

Impact

This doesn’t break backwards compatibility, even if Timber\Image::$caption is used in PHP, because Timber\Core::__get() will automatically resolve to Timber\Image::caption().

Usage Changes

None.

Considerations

Yes, caption() belongs in Timber\Attachment and not Timber\Image, because you can set captions in all kinds of attachments in WordPress, not just images.

Testing

Yes.

[xavivars]

Much better approach!

[gchtr]

@nlemoine I’d be happy about a quick review here, too 😊, thanks!

[nlemoine]

I didn't know hummingbirds can’t walk! Thanks for that fun fact. Here's another one I just stumbled upon about .ch TLD: https://shkspr.mobi/blog/2022/07/dns-esoterica-why-you-cant-dig-switzerland/

Everything looks good :)

[gchtr]

@nlemoine Yeah right? I found tests are a good place to hide fun facts, favorite movie quotes or other phrases that are stuck in your mind.

Whoa, and every day we learn something new. Didn’t know about the Chaosnet network protocol and how it’s connected to .ch a.k.a "Chaos" domains 😆.

Back on topic: Let’s merge this in, then! 🥂