the_excerpt() function return excerpt with different length in page load and ajax request

[Rajinsharwar]

Description

This issue was reported by @sarathlal in WordPress core Trac: https://core.trac.wordpress.org/ticket/59043

Suppose, we are using the_excerpt() function in a post loop that displays posts from a custom WP query for the "Post" post type. Using the same query with pagination parameter and same post loop to display more posts using AJAX.
Recently it was noticed that the excerpt length was different on page load & AJAX load. Another user also raised a related support thread in the support forum.
https://wordpress.org/support/topic/unexpected-behavior-in-post-loop-after-sending-ajax-request/

It was decided that the issue needed to have fixed from Gutenburg at first, on the file:

gutenberg/packages/block-library/src/post-excerpt/index.php

Lines 80 to 95 in d5d8533

	/**
	* If themes or plugins filter the excerpt_length, we need to
	* override the filter in the editor, otherwise
	* the excerpt length block setting has no effect.
	* Returns 100 because 100 is the max length in the setting.
	*/
	if ( is_admin() ||
	defined( 'REST_REQUEST' ) && REST_REQUEST ) {
	add_filter(
	'excerpt_length',
	static function() {
	return 100;
	},
	PHP_INT_MAX
	);
	}

Step-by-step reproduction instructions

Here is the custom code used in theme.

Code in home page template.

<?php
$current_page = get_query_var('paged');
$per_page = get_option('posts_per_page');
$offset = $current_page > 0 ? $per_page * ($current_page-1) : 0;

$blog_args = array(
    'post_type' => 'post',
    'post_status' => 'publish',     
    'posts_per_page' => $per_page,
    'offset' => $offset,
    'order'=>'DESC',
    'orderby'=>'date',
);
$blogs_query = new WP_Query($blog_args);

if ( $blogs_query->have_posts() ) { ?>
        <section class="py-3">
                <div class="container">
                        <p class="section-title">Other Blogs</p>

                        <div id="th-blog-list" class="row posts-grid gx-5 gy-4">
                                <?php 
                while ($blogs_query->have_posts()) : $blogs_query->the_post();
                    $post_id   = get_the_ID();
                    ?>
                    <?php get_template_part('template-parts/post-card'); ?>
                                <?php endwhile; ?>
                        </div>

                        <?php
                        $data = array(
                                'paged' => 2,
                                '_wpnonce' => wp_create_nonce('load-posts'),
                        );
                        global $wp_query;
                        if(isset( $blogs_query->max_num_pages ) && ($blogs_query->max_num_pages > 1)){ ?>
                                <div class="row mb-4 mt-4">
                                        <div class="col-12 text-center">
                                                <span class="spinner-border spinner-border-sm" style="display:none" id="btn-loader" role="status" aria-hidden="true"></span>
                                                <?php
                                                echo '<button type="button" class="btn btn-dark ps-4 pt-2 pe-4 pb-2" id="load-more" '. implode(' ', array_map(
                                                    function ($k, $v) { return "data-" . $k .'="'. htmlspecialchars($v) .'"'; },
                                                    array_keys($data), $data
                                                )) .' />Show more</button>';
                                                ?>
                                        </div>                                          
                                </div>                  
                        <?php } ?>

                </div>
        </section>
<?php } ?>
<?php wp_reset_postdata(); ?>

Code in template-parts/post-card.php

<?php
/**
 * Template part for displaying blog post card
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/
 *
 */
?>

<div class="col-sm-12 col-md-6">
    <div class="post-item">
            <a href="<?php echo get_permalink(get_the_ID()); ?>">
                    <?php echo get_the_post_thumbnail( get_the_ID(), 'full', array( 'class' => 'f-img' ) ); ?>
            </a>
            <p class="title"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></p>
            <p class="short-desc"><?php the_excerpt(); ?></p>
            <p class="author"><?php echo get_the_author(); ?> | <?php echo get_the_date('F j, Y', get_the_ID()); ?></p>
    </div>
</div>
* Code in functions.php for AJAX load more

function th37t_load_more_posts() {
        $req = $_REQUEST;

        if(!isset($_REQUEST['_wpnonce'])){
                 die('stop');
        }

        if(!(wp_verify_nonce( $_REQUEST['_wpnonce'], 'load-posts'))){
                die('stop');
        }

        unset($req["action"]);
        unset($req["_wpnonce"]);

        $per_page = get_option('posts_per_page');
        $default_data = array(
                'post_type' => 'post',
                'posts_per_page' => $per_page,
                'post_status' => 'publish',
                'order'=>'DESC',
                'orderby'=>'date',
        );
        $args = array_merge($default_data, $req);

        $ajaxposts = new WP_Query($args);

        $html = '';
        if($ajaxposts->have_posts()) {
                while($ajaxposts->have_posts()) : $ajaxposts->the_post();
                    ob_start();
                    get_template_part('template-parts/post-card');
                    $html .= ob_get_contents();
                    ob_end_clean();

                endwhile;
        }

        $next_page = false;
        $max_pages = isset($ajaxposts->max_num_pages) ? $ajaxposts->max_num_pages : false;

        $current_page = isset($_REQUEST['paged']) ? $_REQUEST['paged'] : false;

        if( $current_page && $max_pages && $current_page < $max_pages ){
                $next_page = $current_page + 1;
        }
        
        $data = array(
                'html' => $html,
                'next_page' => $next_page,
        );

        wp_send_json($data);
        exit;
}
add_action('wp_ajax_th_load_more_posts', 'th37t_load_more_posts');
add_action('wp_ajax_nopriv_th_load_more_posts', 'th37t_load_more_posts');

Jquery code for "Load more" button

(function($){
	$('#load-more').on('click', function() {
		$('#btn-loader').show();
		$('#load-more').attr("disabled", true);
		var data = $(this).data();

		data['action'] = 'th_load_more_posts';

		$.ajax({
			type: 'POST',
			url: "<?php echo admin_url('admin-ajax.php'); ?>",
			dataType: 'JSON',
			data: data,
			success: function (res) {
				$('#btn-loader').hide();
				if(res.html){
					$('#th-blog-list').append(res.html);
				}

				if(res.next_page){
					$('#load-more').data('paged', res.next_page);
					$('#load-more').attr("disabled", false);
				}else{
					$('#load-more').attr("disabled", true);
				}
			}
		});
	});
})(jQuery);

Now on the initial page load, the excerpt length will be 50 words if there is no filter. But when I click on the "Load More" button, the length will be 100 words.

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[github-actions]

Hi,
This issue has gone 30 days without any activity. This means it is time for a check-in to make sure it is still relevant. If you are still experiencing this issue with the latest versions, you can help the project by responding to confirm the problem and by providing any updated reproduction steps.
Thanks for helping out.

[hellofromtonya]

Hello all 👋

I've closed the Trac ticket as there's nothing actionable in that ticket as the work has to happen here in Gutenberg. But for context, I'll bring over the history.

1. The bug was introduced in WP 6.3 with changeset 56065, see the code here https://core.trac.wordpress.org/changeset/56065#file90.

2. For Core, the severity has been flagged as major with a high priority. As such, I've added the [Priority] High label to denote these levels of concern.

3. There is a PR opened for it. But discussion, review, and testing need to happen. I've also reached out to @anton-vlasenko who is interesting in helping to resolve the issue.

As this issue has been flagged as important within Core, if it gets resolved before WP 6.4 RC1, please include in the cherry picks for package updates. cc @annezazu @bph (6.4 Editor Triage Leads) for awareness.

[anton-vlasenko]

I'm working on this issue.

[apeatling]

@anton-vlasenko There's a PR opened here #53571

[anton-vlasenko]

@anton-vlasenko There's a PR opened here #53571

@apeatling, in my tests, #53571 doesn't resolve the issue. I still see the wrong excerpt length when loading posts via AJAX requests. I'm about to submit another PR, and I'm currently testing it.

[apeatling]

Okay 👍

[anton-vlasenko]

@apeatling I've submitted my pull request. It's ready for testing. I'll add better testing steps tomorrow (it's deep into the night in my time zone), but it can be tested as is.

UPD: I've updated the testing instructions.

[swissspidy]

In https://core.trac.wordpress.org/changeset/58065 I just added support for the excerpt_length parameter in the REST API.

This can now be used in the post excerpt block to properly modify the excerpt length in a non-hacky way.

[colorful-tones]

Hi folks,
We are only one week away from the Beta 1 cut-off date for WordPress 6.6. This issue hasn’t seen any movement in a while, so we (the editor triage leads of the 6.6 release) have decided to remove it from the WordPress 6.6 Editor Tasks project board.