[Plugin: Flexible Recent Posts] Basic support for polylang

Polylang is one of the plugins that add to a WordPress blog the multilingual capability. Have translations of posts, pages, etc. Unfortunately, FRP does not filter posts by language and thus can show post excerpts in a different language than the rest of the blog.
Here is a patch that allows to select languages by typing their slugs.

--- templates/recent-posts-form.php.org2	2012-07-25 14:04:31.000000000 +0600
+++ templates/recent-posts-form.php	2012-10-09 15:10:49.000000000 +0600
@@ -47,6 +47,15 @@
 	<label
 		for="<?php print $this->get_field_id( 'all_posts_link_footer' ); ?>"><?php print __( 'Show after all posts', 'frp' ); ?></label>
 </p>
+<p>
+	<label for="<?php print $this->get_field_id( 'language_filter' ); ?>"><?php print __( 'Filter posts by language(s)' ); ?>:</label>
+	<img src="<?php print $plugin_dir . 'images/help.png'; ?>"
+		 title="<?php _e( 'Filter posts by language. Use the form \'en\' or \'en,ru\' for multiple languages. The list of valid languages is in Settings - Languages. Requires Polylang plugin', 'frp' ); ?>"
+		 class="frp-form-help" alt="<?php _e( 'Help', 'frp' ); ?>">
+	<input class="widefat" id="<?php print $this->get_field_id( 'language_filter' ); ?>"
+		   name="<?php print $this->get_field_name( 'language_filter' ); ?>"
+		   value="<?php print $instance['language_filter']; ?>" type="text">
+</p>
 <h4 class="frp-form-group-title"><?php print __( 'Categories' ); ?><img
 	src="<?php print $plugin_dir . 'images/help.png'; ?>" title="<?php _e( 'Posts categories', 'frp' ); ?>"
 	class="frp-form-help" alt="<?php _e( 'Help', 'frp' ); ?>"></h4>

--- class-recent-posts-widget.php.org2	2012-07-25 14:00:57.000000000 +0600
+++ class-recent-posts-widget.php	2012-10-09 15:09:25.000000000 +0600
@@ -38,7 +38,8 @@
 				'template'                  => '',
 				'theme'				=> 'default',
 				'all_categories'            => true,
-				'categories'                => array()
+				'categories'                => array(),
+				'language_filter'           => ''
 			)
 		);

@@ -71,12 +72,16 @@
 		$instance['all_posts_title'] = htmlspecialchars( $instance['all_posts_title'] );

 		if ( !empty( $instance['categories'] ) || $instance['all_categories'] ) {
-			$posts = get_posts(
-				array(
-					'numberposts' => $instance['number'],
-					'category'    => implode( ',', $instance['categories'] ),
-				)
+			$posts_query = 	array(
+				'numberposts' => $instance['number'],
+				'category'    => implode( ',', $instance['categories'] ),
 			);
+			# Only add the language filter if Polylang is installed
+			if ( function_exists('pll_the_languages') ) {
+			    $posts_query['lang'] = $instance['language_filter'];
+			}
+
+			$posts = get_posts($posts_query);

 			if ( !empty( $posts ) ) {
 				$category_link = ( empty( $instance['all_posts_link'] ) ) ? get_category_link( end( $instance['categories'] ) ) : $instance['all_posts_link'];
@@ -103,6 +108,7 @@
 		$instance['all_posts_link_title'] = isset( $new_instance['all_posts_link_title'] ) ? true : false;
 		$instance['all_posts_link_footer'] = isset( $new_instance['all_posts_link_footer'] ) ? true : false;
 		$instance['all_posts_title'] = strip_tags( $new_instance['all_posts_title'] );
+		$instance['language_filter'] = strip_tags( $new_instance['language_filter'] );
 		$instance['all_posts_link'] = '';

https://www.ads-software.com/extend/plugins/flexible-recent-posts/