[evolution] I#2043 - prefer-plain: 'related' under 'alternative' shows 'html' part

[Milan Crha <mcrha src gnome org>]

commit e558a8b42b3573d74ff94ccee1a90b73831e921c
Author: Milan Crha <mcrha redhat com>
Date:   Mon Sep 26 18:54:19 2022 +0200

    I#2043 - prefer-plain: 'related' under 'alternative' shows 'html' part
    
    Closes https://gitlab.gnome.org/GNOME/evolution/-/issues/2043

 .../prefer-plain/e-mail-parser-prefer-plain.c      | 30 +++++++++++++++-------
 1 file changed, 21 insertions(+), 9 deletions(-)
---
diff --git a/src/modules/prefer-plain/e-mail-parser-prefer-plain.c 
b/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
index af6acb0644..ad3fccdb0c 100644
--- a/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
+++ b/src/modules/prefer-plain/e-mail-parser-prefer-plain.c
@@ -562,9 +562,9 @@ empe_prefer_plain_parse (EMailParserExtension *extension,
                /* Multiparts can represent a text/html message
                 * with other things like embedded images, etc. */
                } else if (camel_content_type_is (ct, "multipart", "*")) {
+                       EMailPart *html_mail_part = NULL;
                        GQueue inner_queue = G_QUEUE_INIT;
                        GList *head, *link;
-                       gboolean multipart_has_html = FALSE;
 
                        e_mail_parser_parse_part (
                                parser, sp, part_id, cancellable, &inner_queue);
@@ -575,21 +575,33 @@ empe_prefer_plain_parse (EMailParserExtension *extension,
                        for (link = head; link != NULL; link = g_list_next (link)) {
                                EMailPart *mail_part = link->data;
 
-                               if (e_mail_part_id_has_substr (mail_part, ".text_html")) {
-                                       multipart_has_html = TRUE;
+                               if (e_mail_part_id_has_substr (mail_part, ".text_html") ||
+                                   /* The HTML part as an HTML source code */
+                                   (emp_pp->mode == PREFER_SOURCE && e_mail_part_id_has_suffix (mail_part, 
".alternative-prefer-plain.-1")) ||
+                                   /* The HTML part converted into text/plain */
+                                   (emp_pp->mode == ONLY_PLAIN && e_mail_part_id_has_suffix (mail_part, 
".alternative-prefer-plain.-1.converted"))) {
+                                       html_mail_part = mail_part;
                                        break;
                                }
                        }
 
-                       if (multipart_has_html && !prefer_html) {
+                       if (html_mail_part && !prefer_html) {
                                if (emp_pp->show_suppressed) {
                                        GQueue suppressed_queue = G_QUEUE_INIT;
+                                       CamelMimePart *inner_part;
 
-                                       e_mail_parser_wrap_as_attachment (
-                                               parser, sp, part_id,
-                                               &suppressed_queue);
+                                       html_mail_part->is_hidden = TRUE;
+                                       inner_part = e_mail_part_ref_mime_part (html_mail_part);
 
-                                       mark_parts_not_printable (&suppressed_queue);
+                                       if (inner_part) {
+                                               e_mail_parser_wrap_as_attachment (
+                                                       parser, inner_part, part_id,
+                                                       &suppressed_queue);
+
+                                               mark_parts_not_printable (&suppressed_queue);
+
+                                               g_clear_object (&inner_part);
+                                       }
 
                                        e_queue_transfer (&suppressed_queue, &inner_queue);
                                } else {
@@ -599,7 +611,7 @@ empe_prefer_plain_parse (EMailParserExtension *extension,
 
                        e_queue_transfer (&inner_queue, &work_queue);
 
-                       has_html |= multipart_has_html;
+                       has_html |= html_mail_part != NULL;
 
                /* Parse other than 'X' (those are custom types) as an attachment */
                } else if (ct && ct->subtype && ct->subtype[0] && ct->subtype[0] != 'x' && ct->subtype[0] != 
'X') {