Custom queries for the posts and query loop blocks

<?php

/**
 * Filter the query for either the Posts block or the Query loop block depending on the ID of the query in question
 * For available query parameters, see https://developer.wordpress.org/reference/classes/wp_query/
 * 
 * Note 1: This is executed AFTER any other query parameters have been set by the block, including post type, inclusions, exclusions, and taxonomies.
 *
 * Note 2: If you're not getting the query results you want, it's possible other plugins are filtering this query as well, as the `pre_get_posts` hook is used here.
 *
 * @param WP_Query $query the query for the block
 * @param array    $block the raw parameters of the block itself
 *
 * @return void
 */
function filter_custom_block_query( WP_Query &$query, array $block ) {

	$query->set( 'post_type', 'my_custom_post_type' );

	// you can use the_email() to get the email that this query is being generated for
	$email = \Groundhogg\the_email();

	// from the email you can get the current contact as well
	$contact = $email->get_contact();

	// Example 1: use contact custom field data to modify the query, such as any post IDs stored in their meta
	$liked_posts = wp_parse_id_list( $contact->get_meta( 'like_posts' ) );
	$query->set( 'post__in', $liked_posts );

	// Example 2: we can get the user ID from the contact record, if there's one linked, and from that we can filter based on author
	$user_id = $contact->get_user_id();
	// if there is a linked user
	if ( $user_id ){
		$query->set( 'author', $user_id );
	}

	// Example 3: retrieve posts that have a custom field equal to the value of a custom field in the contact record
	$custom_field = $contact->get_meta( 'custom_field' );
	$query->set( 'meta_query', [
		[
			'key'     => 'custom_field',
			'compare' => '=',
			'value'   => $custom_field,
		]
	] );

	// Example 4: retrieve posts that have the same tags as the contact has, given that the tags have the same slugs
	$tags = $contact->get_tags(true );
	$tag_slugs = \Groundhogg\parse_tag_list( $tags, 'slug' );
	$query->set( 'tag_slug__in', $tag_slugs ); // or 'tag_slug__and'
}

add_action( 'groundhogg/block_query/my_custom_query', 'filter_custom_block_query', 10, 2 );