add a test that fails if 'References:'-header is missing

src/chat.rs

@@ -3072,6 +3072,7 @@ mod tests {
     use crate::chatlist::Chatlist;
     use crate::constants::{DC_GCL_ARCHIVED_ONLY, DC_GCL_NO_SPECIALS};
     use crate::contact::Contact;
+    use crate::dc_receive_imf::dc_receive_imf;
     use crate::test_utils::TestContext;
 
     #[async_std::test]
@@ -3844,4 +3845,65 @@ mod tests {
         assert!(chat_id.is_self_talk(&ctx).await.unwrap());
         assert_eq!(blocked, Blocked::Not);
     }
+
+    #[async_std::test]
+    async fn test_group_with_removed_message_id() {
+        // Alice creates a group with Bob, sends a message to bob
+        let alice = TestContext::new_alice().await;
+        let bob = TestContext::new_bob().await;
+        alice
+            .set_config(Config::ShowEmails, Some("2"))
+            .await
+            .unwrap();
+        bob.set_config(Config::ShowEmails, Some("2")).await.unwrap();
+
+        let (contact_id, _) =
+            Contact::add_or_lookup(&alice, "", "bob@example.net", Origin::ManuallyCreated)
+                .await
+                .unwrap();
+        let alice_chat_id = create_group_chat(&alice, ProtectionStatus::Unprotected, "grp")
+            .await
+            .unwrap();
+        let alice_chat = Chat::load_from_db(&alice, alice_chat_id).await.unwrap();
+        add_contact_to_chat(&alice, alice_chat_id, contact_id).await;
+        assert_eq!(get_chat_contacts(&alice, alice_chat_id).await.len(), 2);
+        send_text_msg(&alice, alice_chat_id, "hi!".to_string())
+            .await
+            .ok();
+        assert_eq!(get_chat_msgs(&alice, alice_chat_id, 0, None).await.len(), 1);
+
+        // Alice has an SMTP-server replacing the `Message-ID:`-header (as done eg. by outlook.com).
+        let msg = alice.pop_sent_msg().await.payload();
+        assert_eq!(msg.match_indices("Gr.").count(), 2);
+        let msg = msg.replace("Message-ID: <Gr.", "Message-ID: <XXX");
+        assert_eq!(msg.match_indices("Gr.").count(), 1);
+
+        // Bob receives this message, he may detect group by `References:`- or `Chat-Group:`-header
+        dc_receive_imf(&bob, msg.as_bytes(), "INBOX", 1, false)
+            .await
+            .unwrap();
+        let msg = bob.get_last_msg().await;
+
+        let bob_chat = Chat::load_from_db(&bob, msg.chat_id).await.unwrap();
+        assert_eq!(bob_chat.grpid, alice_chat.grpid);
+
+        // Bob answers - simulate a normal MUA by not setting `Chat-*`-headers;
+        // moreover, Bob's SMTP-server also replaces the `Message-ID:`-header
+        send_text_msg(&bob, bob_chat.id, "ho!".to_string())
+            .await
+            .ok();
+        let msg = bob.pop_sent_msg().await.payload();
+        let msg = msg.replace("Message-ID: <Gr.", "Message-ID: <XXX");
+        let msg = msg.replace("Chat-", "XXXX-");
+        assert_eq!(msg.match_indices("Chat-").count(), 0);
+
+        // Alice receives this message - she can still detect the group by the `References:`-header
+        dc_receive_imf(&alice, msg.as_bytes(), "INBOX", 2, false)
+            .await
+            .unwrap();
+        let msg = alice.get_last_msg().await;
+        assert_eq!(msg.chat_id, alice_chat_id);
+        assert_eq!(msg.text, Some("ho!".to_string()));
+        assert_eq!(get_chat_msgs(&alice, alice_chat_id, 0, None).await.len(), 2);
+    }
 }