wp_filter_wp_template_unique_post_slug( string $override_slug, string $slug, int $post_ID, string $post_status, string $post_type )

Source

File: wp-includes/theme-templates.php

function wp_filter_wp_template_unique_post_slug( $override_slug, $slug, $post_ID, $post_status, $post_type ) {
	if ( 'wp_template' !== $post_type ) {
		return $override_slug;
	}

	if ( ! $override_slug ) {
		$override_slug = $slug;
	}

	/*
	 * Template slugs must be unique within the same theme.
	 * TODO - Figure out how to update this to work for a multi-theme environment.
	 * Unfortunately using `get_the_terms()` for the 'wp-theme' term does not work
	 * in the case of new entities since is too early in the process to have been saved
	 * to the entity. So for now we use the currently activated theme for creation.
	 */
	$theme = wp_get_theme()->get_stylesheet();
	$terms = get_the_terms( $post_ID, 'wp_theme' );
	if ( $terms && ! is_wp_error( $terms ) ) {
		$theme = $terms[0]->name;
	}

	$check_query_args = array(
		'post_name__in'  => array( $override_slug ),
		'post_type'      => $post_type,
		'posts_per_page' => 1,
		'no_found_rows'  => true,
		'post__not_in'   => array( $post_ID ),
		'tax_query'      => array(
			array(
				'taxonomy' => 'wp_theme',
				'field'    => 'name',
				'terms'    => $theme,
			),
		),
	);
	$check_query      = new WP_Query( $check_query_args );
	$posts            = $check_query->posts;

	if ( count( $posts ) > 0 ) {
		$suffix = 2;
		do {
			$query_args                  = $check_query_args;
			$alt_post_name               = _truncate_post_slug( $override_slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
			$query_args['post_name__in'] = array( $alt_post_name );
			$query                       = new WP_Query( $query_args );
			$suffix++;
		} while ( count( $query->posts ) > 0 );
		$override_slug = $alt_post_name;
	}

	return $override_slug;
}