ElasticPress - Polylang

elasticpress-polylang.php

<?php
/**
 * Filter Elasticsearch posts by current language.
 */
add_filter( 'ep_formatted_args', function( $formatted_args, $args ) {

	if ( function_exists( 'pll_current_language' ) ) {
		$lang = pll_current_language();

		if ( $lang !== false ) {
			$term = get_term_by( 'slug', $lang, 'language' );

			$formatted_args['post_filter']['bool']['must'][] = [
				'term' => [
					'terms.language.term_taxonomy_id' => $term->term_id
				]
			];
		}
	}

	return $formatted_args;
}, 10, 2);

/**
 * Add language taxonomy to Elasticsearch database.
 */
add_filter( 'ep_sync_taxonomies', function( $selected_taxonomies, $post ) {
	if ( function_exists( 'pll_is_translated_post_type' ) ) {
		if ( pll_is_translated_post_type( $post->post_type ) ) {
			$selected_taxonomies[] = get_taxonomy( 'language' );
		}
	}

	return $selected_taxonomies;
}, 10, 2 );