How to add categories to WordPress block patterns?

I'm trying to create categories for WP block patterns. So far I have:

// Custom taxonomy for wp_block post type
function register_patterns_taxonomy() {
$labels = array(
'name' => 'Pattern category',
'singular_name' => 'Pattern category',
'search_items' => 'Search Patterns categories',
'all_items' => 'All Patterns categories',
'parent_item' => 'Parent Pattern category',
'parent_item_colon' => 'Parent Pattern category:',
'edit_item' => 'Edit Pattern category',
'update_item' => 'Update Pattern category',
'add_new_item' => 'Add New Pattern category',
'new_item_name' => 'New Pattern category Name',
'menu_name' => 'Patterns categories',
);
$args = array(
'labels' => $labels,
'hierarchical' => true,
'public' => true,
'show_ui' => true,
'show_admin_column' => true,
'query_var' => true,
'show_in_rest' => true,
'rewrite' => array( 'slug' => 'patterns_categories' ),
);
register_taxonomy( 'patterns_categories', array( 'wp_block' ), $args );
}
add_action( 'init', 'register_patterns_taxonomy' );
// creating patters categories by taxonomy terms
function create_block_pattern_category_for_terms() {
$taxonomy = 'patterns_categories'; // Zmień na nazwę swojej taksonomii
$terms = get_terms( array(
'taxonomy' => $taxonomy,
'hide_empty' => false, // Pobierz wszystkie termy, także te puste
) );
foreach ( $terms as $term ) {
$pattern_category = sanitize_title( $term->name ); // Tworzenie unikalnej nazwy kategorii
$pattern_category_exists = get_terms( 'patterns_categories', array( 'slug' => $pattern_category ) );
register_block_pattern_category(
$term->slug,
array( 'label' => __( $term->name, 'wpdocs-my-plugin' ) )
);
}
}
add_action( 'init', 'create_block_pattern_category_for_terms' );

and that works fine, I have custom taxonomy visible in block pattern post, also I successfully created blocks pattern categories based on custom taxonomy terms.

But now, I need to add somehow these terms to blocks patterns.

My idea is using register_block_pattern() for each post in wp_block post type, and add properly: title, content and categories. So I've tried:

// trying to create patterns
$args = array(
'post_type' => 'wp_block',
'posts_per_page' => -1,
);
$posts = get_posts($args);
foreach ($posts as $post) {
setup_postdata($post);
$title = get_the_title();
$content = get_the_content();
// Fetch terms associated with this post
$terms = wp_get_post_terms($post->ID, 'patterns_categories', array('fields' => 'slugs'));
// Create block pattern
register_block_pattern(
'handy-options/' . $title,
array(
'title'       => $title,
'description' => _x('Two horizontal buttons, the left button is filled in, and the right button is outlined.', 'Block pattern description', 'theme-slug'),
'categories'  => $terms,
'content'     => wp_json_encode($content),
)
);
}
wp_reset_postdata(); 

but I don't know is this a good way - although new block patters are created with correct title, I can't add terms and content correctly.

Any advice, idea?

When you come to register your block pattern, it's best to add that to a hook which loads the patterns only when editing or adding a post/page etc.

The main error is the JSON-encoded content. Just add the post_content, and it'll display just fine.

add_action( 'load-post.php', 'register_theme_patterns' );
add_action( 'load-post-new.php', 'register_theme_patterns' );

function register_theme_patterns()
{

	if ( !function_exists( 'register_block_pattern' ) )
	{
		return;
	}

	// Query all published patterns.
	$patterns = new WP_Query( [ 
		'post_type' => 'wp_block',
		'number_posts' => -1
	] );

	if ( $patterns->have_posts() )
	{

		while ( $patterns->have_posts() )
		{
			$patterns->the_post();
			global $post;

			$terms = wp_get_post_terms( $post->ID, 'patterns_categories', array( 'fields' => 'slugs' ) );

			register_block_pattern(
				sprintf( 'theme-patterns/%s', sanitize_key( $post->post_name ) ),
				[ 
					'title' => wp_strip_all_tags( $post->post_title ),
					'content' => $post->post_content,
					'categories' => $terms
				]
			);
		}
	}

	wp_reset_postdata();
}

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