feat: make text/calendar alternative available as an attachment

src/mimeparser.rs

@@ -1099,6 +1099,32 @@ impl MimeMessage {
                     }
                 }
 
+                // Explicitly look for a `text/calendar` part.
+                // Messages conforming to <https://datatracker.ietf.org/doc/html/rfc6047>
+                // contain `text/calendar` part as an alternative
+                // to the text or HTML representation.
+                //
+                // While we cannot display `text/calendar` and therefore do not prefer it,
+                // we still make it available by presenting as an attachment
+                // with a generic filename.
+                for cur_data in mail.subparts.iter().rev() {
+                    let mimetype = cur_data.ctype.mimetype.parse::<Mime>()?;
+                    if mimetype.type_() == mime::TEXT && mimetype.subtype() == "calendar" {
+                        let filename = get_attachment_filename(context, cur_data)?
+                            .unwrap_or_else(|| "calendar.ics".to_string());
+                        self.do_add_single_file_part(
+                            context,
+                            Viewtype::File,
+                            mimetype,
+                            &mail.ctype.mimetype.to_lowercase(),
+                            &mail.get_body_raw()?,
+                            &filename,
+                            is_related,
+                        )
+                        .await?;
+                    }
+                }
+
                 if !any_part_added {
                     for cur_part in mail.subparts.iter().rev() {
                         if self

src/receive_imf/receive_imf_tests.rs

@@ -5565,7 +5565,8 @@ async fn test_lookup_key_contact_by_address_self() -> Result<()> {
 /// messages with three parts:
 /// `text/plain`, `text/html` and `text/calendar`.
 ///
-/// We display `text/plain` part in this case.
+/// We display `text/plain` part in this case,
+/// but .ics file is available as an attachment.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_calendar_alternative() -> Result<()> {
     let mut tcm = TestContextManager::new();
@@ -5574,11 +5575,13 @@ async fn test_calendar_alternative() -> Result<()> {
     let msg = receive_imf(t, raw, false).await?.unwrap();
     assert_eq!(msg.msg_ids.len(), 1);
 
-    let text_msg = Message::load_from_db(t, msg.msg_ids[0]).await?;
+    let calendar_msg = Message::load_from_db(t, msg.msg_ids[0]).await?;
-    assert_eq!(text_msg.text, "Subject was here – Hello!");
+    assert_eq!(calendar_msg.text, "Subject was here – Hello!");
-    assert_eq!(text_msg.viewtype, Viewtype::Text);
+    assert_eq!(calendar_msg.viewtype, Viewtype::File);
-    assert!(text_msg.has_html());
+    assert_eq!(calendar_msg.get_filename().unwrap(), "calendar.ics");
-    let html = text_msg.get_id().get_html(t).await.unwrap().unwrap();
+
+    assert!(calendar_msg.has_html());
+    let html = calendar_msg.get_id().get_html(t).await.unwrap().unwrap();
     assert_eq!(html, "<b>Hello!</b>");
 
     Ok(())