fix: Don't resort re-sent message to the bottom (#8145)

We shouldn't just revert ad7f873c68 because then we won't be able to
normally transfer a backup from a device having clock a bit in the future.

INDEXED BY msgs_index7 is to prevent SQLite from downgrading to using msgs_index2 which has less
ordering.

src/chat.rs

@@ -2947,17 +2947,19 @@ pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -
             "
 UPDATE msgs SET
     timestamp=(
-        SELECT MAX(timestamp) FROM msgs WHERE
+        SELECT MAX(timestamp) FROM msgs INDEXED BY msgs_index7 WHERE
             -- From `InFresh` to `OutMdnRcvd` inclusive except `OutDraft`.
             state IN(10,13,16,18,20,24,26,28) AND
             hidden IN(0,1) AND
-            chat_id=?
+            chat_id=? AND
+            id<=?
     ),
     pre_rfc724_mid=?, subject=?, param=?
 WHERE id=?
             ",
             (
                 msg.chat_id,
+                msg.id,
                 &msg.pre_rfc724_mid,
                 &msg.subject,
                 msg.param.to_string(),

src/chat/chat_tests.rs

@@ -2692,6 +2692,49 @@ async fn test_resend_own_message() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_resend_doesnt_resort_msg() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+    let alice_grp = create_group(alice, "").await?;
+    let sent1 = alice.send_text(alice_grp, "hi").await;
+    let sent1_ts = Message::load_from_db(alice, sent1.sender_msg_id)
+        .await?
+        .timestamp_sort;
+
+    SystemTime::shift(Duration::from_secs(60));
+    add_contact_to_chat(alice, alice_grp, alice.add_or_lookup_contact_id(bob).await).await?;
+    let sent2 = alice
+        .send_text(
+            alice_grp,
+            "Let's test resending, there are very few tests on it",
+        )
+        .await;
+    let resent_msg_id = sent1.sender_msg_id;
+    resend_msgs(alice, &[resent_msg_id]).await?;
+    assert_eq!(
+        resent_msg_id.get_state(alice).await?,
+        MessageState::OutPending
+    );
+    alice.pop_sent_msg().await;
+    assert_eq!(
+        resent_msg_id.get_state(alice).await?,
+        MessageState::OutDelivered
+    );
+    assert_eq!(
+        Message::load_from_db(alice, sent1.sender_msg_id)
+            .await?
+            .timestamp_sort,
+        sent1_ts
+    );
+    assert_eq!(
+        alice.get_last_msg_id_in(alice_grp).await,
+        sent2.sender_msg_id
+    );
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_resend_foreign_message_fails() -> Result<()> {
     let mut tcm = TestContextManager::new();

src/test_utils.rs

@@ -834,17 +834,24 @@ ORDER BY id"
         assert_eq!(received.chat_id, DC_CHAT_ID_TRASH);
     }
 
+    /// Gets the most recent message ID of a chat.
+    ///
+    /// Panics on errors or if the most recent message is a marker.
+    pub async fn get_last_msg_id_in(&self, chat_id: ChatId) -> MsgId {
+        let msgs = chat::get_chat_msgs(&self.ctx, chat_id).await.unwrap();
+        if let ChatItem::Message { msg_id } = msgs.last().unwrap() {
+            *msg_id
+        } else {
+            panic!("Wrong item type");
+        }
+    }
+
     /// Gets the most recent message of a chat.
     ///
     /// Panics on errors or if the most recent message is a marker.
     pub async fn get_last_msg_in(&self, chat_id: ChatId) -> Message {
-        let msgs = chat::get_chat_msgs(&self.ctx, chat_id).await.unwrap();
+        let msg_id = self.get_last_msg_id_in(chat_id).await;
-        let msg_id = if let ChatItem::Message { msg_id } = msgs.last().unwrap() {
+        Message::load_from_db(&self.ctx, msg_id).await.unwrap()
-            msg_id
-        } else {
-            panic!("Wrong item type");
-        };
-        Message::load_from_db(&self.ctx, *msg_id).await.unwrap()
     }
 
     /// Gets the most recent message over all chats.