Check for nextpage to display page links for paginated posts

[alberto-marin]

Hi,
The "core/nextpage" it's a child of "core/post-content" but within the post-content there's no reference to it.

After getting the value for $post_id we could see that the block core/nextpage exists by using something like this:

$blocks = parse_blocks( get_post($post_id)->post_content );
var_dump($blocks);

What is missing here is the ability to detect this "child" block. After applying the filter to the_content we could check and call the function that displays page links:

	// Check for nextpage to display page links for paginated posts
	$nextpage = has_block('nextpage') ? wp_link_pages(['echo' => 0]) : false;
	if ( false !== $nextpage ) {
		$content = get_the_content() . $nextpage;
	}

I have tested it with the official wordpress themes from twentytwentynine to twentytwentytwo, and it works well.

This fix is related to this issue: #29484

Note that get_the_content() doesn't need the null and false attributes because those are the function defaults.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[github-actions]

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[Mamaduka]

Thanks for contributing, @alberto-marin.

I'm wondering if this should be a separate block. @carolinan, @kjellr, what do you think?

[carolinan]

@Mamaduka I did not understand; the page break is already a block.

From the issue:
#29484

I have confirmed that if I add a page break block to a theme that supports full site editing, the block shows correctly in the site editor and post editor, but not the front.

The page break block also does not work with traditional/PHP based themes that does not add wp_link_pages(). See https://developer.wordpress.org/reference/functions/wp_link_pages/

Looks like without wp_link_pages, <!‐‐nextpage‐‐> which is saved in https://github.com/WordPress/gutenberg/blob/trunk/packages/block-library/src/nextpage/save.js#L7 is not understood?

[carolinan]

Don't we need to add this in a new .php file for nextpage?
https://github.com/WordPress/gutenberg/tree/trunk/packages/block-library/src/nextpage

[Mamaduka]

@carolinan, sorry for the confusion.

I meant "Page Links" as a separate/new block. The block will give theme authors more flexibility in displaying these links + styling options.

[kjellr]

I meant "Page Links" as a separate/new block. The block will give theme authors more flexibility in displaying these links + styling options.

I think eventually, we should just follow the lead of what we do for standard query pagination. In that case, there are three separate blocks:

• Previous Page
• Page Numbers
• Next Page

[Mamaduka]

@kjellr, this is slightly different from Query pagination blocks.

You have separate methods (get_next_posts_link, paginate_links, etc.) handling each part of the functionality for Query blocks. While for the post's pages, we have a single method that handles all the above. It is the reason I was suggesting one new block.

[kjellr]

That sounds like a technical reason, not a UX reason though — I think there's value in making pagination consistent wherever it's available so users don't have to re-learn it every time.

For the near term though, I don't have a strong preference about whether that's a separate block or not. That seems like a decent idea, but as long as this is showing up again for block themes I think we're good for now.

[Mamaduka]

Changes look good. Thanks, @alberto-marin.

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[Mamaduka]

@noisysocks, I'm adding a backport label for this PR. It's a small change and adds missing behavior.