PHP warning in filter_graph when post is not in Yoast index

[mattwatsoncodes]

When a post type is excluded from the Yoast SEO index using the wpseo_indexable_excluded_post_types filter, the post may not have a proper indexable object or ID when passed into Yoast’s filter_graph hook (using the $context argument). Co-Authors Plus currently assumes that a valid post object within the $context and therefore the ID will be available within this filter, which can trigger warnings.

The problematic function is here:

Co-Authors-Plus/php/integrations/yoast.php

Lines 149 to 223 in 14725a6

	/**
	* Filters the graph output to add authors.
	*
	* @param array $data The schema graph.
	* @param Meta_Tags_Context $context Context object.
	*
	* @return array The (potentially altered) schema graph.
	*/
	public static function filter_graph( $data, $context ): array {
	if ( ! is_singular() ) {
	return $data;
	}
	if ( ! function_exists( 'get_coauthors' ) ) {
	return $data;
	}
	/**
	* Contains the authors from the Co-Authors Plus plugin.
	*
	* @var WP_User[] $author_objects
	*/
	$author_objects = get_coauthors( $context->post->ID );
	$ids = [];
	$authors = [];
	// Add the authors to the schema.
	foreach ( $author_objects as $author ) {
	$author_generator = new CoAuthor();
	$author_generator->context = $context;
	$author_generator->helpers = YoastSEO()->helpers;
	if ( $author instanceof WP_User ) {
	$author_data = $author_generator->generate_from_user_id( $author->ID );
	} elseif ( ! empty( $author->type ) && $author->type === 'guest-author' ) {
	$author_data = $author_generator->generate_from_guest_author( $author );
	}
	if ( ! empty( $author_data ) ) {
	$ids[] = [ '@id' => $author_data['@id'] ];
	$authors[] = $author_data;
	}
	}
	$schema_types = new Schema_Types();
	$article_types = array_column( $schema_types->get_article_type_options(), 'value' );
	// Change the author reference to reference our multiple authors.
	$add_to_graph = false;
	foreach ( $data as $key => $piece ) {
	if ( in_array( $piece['@type'], $article_types, true ) ) {
	$data[ $key ]['author'] = $ids;
	$add_to_graph = true;
	break;
	}
	}
	if ( $add_to_graph ) {
	// Clean all Persons from the schema, as the user stored as post owner might be incorrectly added if the post has only guest authors as authors.
	$data = array_filter(
	$data,
	function( $piece ) {
	return empty( $piece['@type'] ) || $piece['@type'] !== 'Person';
	}
	);
	if ( ! empty( $author_data ) ) {
	if ( $context->site_represents !== 'person' || $author->ID !== $context->site_user_id ) {
	$data = array_merge( $data, $authors );
	}
	}
	}
	return $data;
	}

This issue was observed with a custom post type that is excluded via:

add_filter( 'wpseo_indexable_excluded_post_types', function( $post_types ) {
    $post_types[] = 'example-post-type';
    return $post_types;
});

The filter_graph filter still runs for this post type, even though it is not Yoast-indexable. However, Co-Authors tries to access get_coauthors( $context->post->ID ), which can result in an error if $context->post is missing due to the post not being indexed.

Proposed Solution

I propose adding a check to ensure the post and the post->ID exist within the $context that is passed to the filter, before trying to attach co-authors to it.