List related text/html part as attachment in plain text mode (#1488677)

CHANGELOG

@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- List related text/html part as attachment in plain text mode (#1488677)
 - Use IMAP BINARY (RFC3516) extension to fetch message/part bodies
 - Fix folder creation under public namespace root (#1488665)
 - Fix so "Edit as new" on draft creates a new message (#1488687)

program/include/rcube_message.php

@@ -494,9 +494,14 @@ class rcube_message
                     }
 
                     // list as attachment as well
-                    if (!empty($mail_part->filename))
+                    if (!empty($mail_part->filename)) {
+                        $this->attachments[] = $mail_part;
+                    }
+                    // list html part as attachment (here the part is most likely inside a multipart/related part)
+                    else if ($this->parse_alternative && ($secondary_type == 'html' && !$this->opt['prefer_html'])) {
                         $this->attachments[] = $mail_part;
                     }
+                }
                 // part message/*
                 else if ($primary_type == 'message') {
                     $this->parse_structure($mail_part, true);