fix: Assign encrypted partially downloaded group messages to 1:1 chat (#4757)

Before they were trashed. Note that for unencrypted ones DC works as expected creating the requested
group immediately because Chat-Group-Id is duplicated in the Message-Id header and Subject is
fetched.

src/mimeparser.rs

@@ -110,7 +110,7 @@ pub(crate) struct MimeMessage {
 
     /// The decrypted, raw mime structure.
     ///
-    /// This is non-empty only if the message was actually encrypted.  It is used
+    /// This is non-empty iff `is_mime_modified` and the message was actually encrypted. It is used
     /// for e.g. late-parsing HTML.
     pub decoded_data: Vec<u8>,
 

src/receive_imf.rs

@@ -596,6 +596,7 @@ async fn add_parts(
             if let Some((new_chat_id, new_chat_id_blocked)) = create_or_lookup_group(
                 context,
                 mime_parser,
+                is_partial_download.is_some(),
                 if test_normal_chat.is_none() {
                     allow_creation
                 } else {
@@ -822,6 +823,7 @@ async fn add_parts(
                 if let Some((new_chat_id, new_chat_id_blocked)) = create_or_lookup_group(
                     context,
                     mime_parser,
+                    is_partial_download.is_some(),
                     allow_creation,
                     Blocked::Not,
                     from_id,
@@ -1518,6 +1520,7 @@ async fn is_probably_private_reply(
 async fn create_or_lookup_group(
     context: &Context,
     mime_parser: &mut MimeMessage,
+    is_partial_download: bool,
     allow_creation: bool,
     create_blocked: Blocked,
     from_id: ContactId,
@@ -1648,7 +1651,7 @@ async fn create_or_lookup_group(
 
     if let Some(chat_id) = chat_id {
         Ok(Some((chat_id, chat_id_blocked)))
-    } else if mime_parser.decrypting_failed {
+    } else if is_partial_download || mime_parser.decrypting_failed {
         // It is possible that the message was sent to a valid,
         // yet unknown group, which was rejected because
         // Chat-Group-Name, which is in the encrypted part, was

src/receive_imf/tests.rs

@@ -3725,3 +3725,87 @@ async fn test_download_later() -> Result<()> {
 
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_create_group_with_big_msg() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = tcm.alice().await;
+    let bob = tcm.bob().await;
+    let ba_contact = Contact::create(
+        &bob,
+        "alice",
+        &alice.get_config(Config::Addr).await?.unwrap(),
+    )
+    .await?;
+    let file_bytes = include_bytes!("../../test-data/image/screenshot.png");
+
+    let bob_grp_id = create_group_chat(&bob, ProtectionStatus::Unprotected, "Group").await?;
+    add_contact_to_chat(&bob, bob_grp_id, ba_contact).await?;
+    let mut msg = Message::new(Viewtype::Image);
+    msg.set_file_from_bytes(&bob, "a.jpg", file_bytes, None)
+        .await?;
+    let sent_msg = bob.send_msg(bob_grp_id, &mut msg).await;
+    assert!(!msg.get_showpadlock());
+
+    alice.set_config(Config::DownloadLimit, Some("1")).await?;
+    assert_eq!(alice.download_limit().await?, Some(MIN_DOWNLOAD_LIMIT));
+    let msg = alice.recv_msg(&sent_msg).await;
+    assert_eq!(msg.download_state, DownloadState::Available);
+    let alice_grp = Chat::load_from_db(&alice, msg.chat_id).await?;
+    assert_eq!(alice_grp.typ, Chattype::Group);
+    assert_eq!(alice_grp.name, "Group");
+    assert_eq!(
+        chat::get_chat_contacts(&alice, alice_grp.id).await?.len(),
+        2
+    );
+
+    alice.set_config(Config::DownloadLimit, None).await?;
+    let msg = alice.recv_msg(&sent_msg).await;
+    assert_eq!(msg.download_state, DownloadState::Done);
+    assert_eq!(msg.state, MessageState::InFresh);
+    assert_eq!(msg.viewtype, Viewtype::Image);
+    assert_eq!(msg.chat_id, alice_grp.id);
+    let alice_grp = Chat::load_from_db(&alice, msg.chat_id).await?;
+    assert_eq!(alice_grp.typ, Chattype::Group);
+    assert_eq!(alice_grp.name, "Group");
+    assert_eq!(
+        chat::get_chat_contacts(&alice, alice_grp.id).await?.len(),
+        2
+    );
+
+    let ab_chat_id = tcm.send_recv_accept(&alice, &bob, "hi").await.chat_id;
+    // Now Bob can send encrypted messages to Alice.
+
+    let bob_grp_id = create_group_chat(&bob, ProtectionStatus::Unprotected, "Group1").await?;
+    add_contact_to_chat(&bob, bob_grp_id, ba_contact).await?;
+    let mut msg = Message::new(Viewtype::Image);
+    msg.set_file_from_bytes(&bob, "a.jpg", file_bytes, None)
+        .await?;
+    let sent_msg = bob.send_msg(bob_grp_id, &mut msg).await;
+    assert!(msg.get_showpadlock());
+
+    alice.set_config(Config::DownloadLimit, Some("1")).await?;
+    let msg = alice.recv_msg(&sent_msg).await;
+    assert_eq!(msg.download_state, DownloadState::Available);
+    // Until fully downloaded, an encrypted message must sit in the 1:1 chat.
+    assert_eq!(msg.chat_id, ab_chat_id);
+
+    alice.set_config(Config::DownloadLimit, None).await?;
+    let msg = alice.recv_msg(&sent_msg).await;
+    assert_eq!(msg.download_state, DownloadState::Done);
+    assert_eq!(msg.state, MessageState::InFresh);
+    assert_eq!(msg.viewtype, Viewtype::Image);
+    assert_ne!(msg.chat_id, ab_chat_id);
+    let alice_grp = Chat::load_from_db(&alice, msg.chat_id).await?;
+    assert_eq!(alice_grp.typ, Chattype::Group);
+    assert_eq!(alice_grp.name, "Group1");
+    assert_eq!(
+        chat::get_chat_contacts(&alice, alice_grp.id).await?.len(),
+        2
+    );
+
+    // The big message must go away from the 1:1 chat.
+    assert_eq!(alice.get_last_msg_in(ab_chat_id).await.text, "hi");
+
+    Ok(())
+}