Add 'wp-block-button__link' to the link selector's ':not' collection

[pbking]

What?

Add wp-block-button__link to the link selector's :not collection

Why?

In #40260 the .wp-element-button class was introduced and link element styles were applied to all a anchor elements but excluded those with that class.
However the class is only introduced on new content (or when old content is re-serialized). So any Button Blocks created prior to that change have the link styles applied.

Expected:

Before:

After:

How?

This adds the .wp-block-button__link to the anchor selector excluding any button that has that class from the anchor styles.

Testing Instructions

Load a site that has content created prior to the #40260 change. (I imported the content from this site and used this page).

Configure your theme with a link color via theme.json :

{
	"styles": {
		"elements": {
			"link": {
				"color": {
					"text": "green"
				}
			}
		}
	}
}	

Note that before this change the button block is rendered with the color assigned to the link element.
Apply the change and note that the button block is no longer rendered with the color assigned to the link element.

[matiasbenedetto]

Thanks for the context in the PR description.
With this change, both legacy and new buttons and links work as expected. LGTM

[pbking]

Looks like some unit tests need to change for this to pass.

[aristath]

Shouldn't this be like this instead? 🤔

Suggested change

	'link' => 'a:not(.wp-element-button, .wp-block-button__link)',
	'link' => 'a:not(.wp-element-button):not(.wp-block-button__link)',

[pbking]

This seems to have been addressed by this change in a simpler/better way. Closing this in preference to that.