feature request: duplication of post slugs

Hello,

I would very much love this feature too.

I was able to find an old topic with this workaround

global $polylang;
// Check if Polylang_Base exists and if $polylang is the right object
if(is_admin() && class_exists('Polylang_Base') && $polylang instanceof Polylang_Base){

	// The wp_unique_post_slug filter is applied only after WordPress checks if the slug is unique and adds suffix otherwise
	// the function returns unique post slug within language
	add_filter('wp_unique_post_slug', 'unique_slug_in_language', 10, 5);
	function unique_slug_in_language($slug, $post_ID, $post_status, $post_type, $post_parent = 0){
		global $polylang, $wpdb;

		// Get language of a post
		$lang = $polylang->get_post_language($post_ID);
		// return the slug if Polylang does not return post language
		if(empty($lang))
			return $slug;

		// Remove suffix if it was added
		// this might remove any dash and number at the end of a slug
		$new_slug = isset($_POST['new_slug'])? sanitize_title($_POST['new_slug']) : preg_replace('@-\d$@', '', $slug);

		// Return slug if it was not changed
		if($new_slug == $slug)
			return $slug;

		// prepare statements to filter by language
		$join = $wpdb->prepare(" INNER JOIN $wpdb->term_relationships AS pll_tr ON pll_tr.object_id = ID");
		$where_lang = $wpdb->prepare(" AND pll_tr.term_taxonomy_id = %d", $lang->term_id);

		$hierarchical_post_types = get_post_types( array('hierarchical' => true) );

		// Polylang does not translate attachements - skip if it is one
		if ( 'attachment' == $post_type ) {
			return $slug;

		} elseif ( in_array( $post_type, $hierarchical_post_types ) ) {
			// Page slugs must be unique within their own trees. Pages are in a separate
			// namespace than posts so page slugs are allowed to overlap post slugs.
			$check_sql = "SELECT post_name FROM $wpdb->posts
			$join
			WHERE post_name = %s AND post_type IN ( '" . implode( "', '", esc_sql( $hierarchical_post_types ) ) . "' ) AND ID != %d AND post_parent = %d
			$where_lang
			LIMIT 1";
			$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $new_slug, $post_ID, $post_parent ) );
			if(!$post_name_check)
				return $new_slug;

		} else {
			// Post slugs must be unique across all posts.
			$check_sql = "SELECT post_name FROM $wpdb->posts
			$join
			WHERE post_name = %s AND post_type = %s AND ID != %d
			$where_lang
			LIMIT 1";
			$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $new_slug, $post_type, $post_ID ) );
			if(!$post_name_check)
				return $new_slug;
		}
		return $slug;
	}

}

But it’s not working with new versions of Polylang and i’m not capable of modifying it by myself.

Could it even work with current / 1.4.2 version of Polylang? And if so, is someone able to modify it?

Thanks in advance

https://wordpress.org/plugins/polylang/