fix: Emit MsgsNoticed on receipt of an IMAP-seen message

`imap::Session::sync_seen_flags()` emits `MsgsNoticed` for existing messages seen on other devices,
so `receive_imf` should do the same when it receives a seen message. Otherwise a multi-device user
may see a new message notification on device A, just swipe it, then see another new message
notification and mark it as read, and when a device B goes online, it will show a notification for
the first message, and it won't be removed because `MsgsNoticed` isn't emitted. I have checked this
with my DC Android and Desktop. With this fix the notification can be removed if UIs handle
`MsgsNoticed` accordingly, though currently i can't achieve this behaviour in Desktop.

Also add blocked chat's messages and silent group changes messages as `InNoticed` instead of
`InSeen`, they don't need to cause `MsgsNoticed` events. This doesn't change any UX, checked this in
Desktop.

src/chat/chat_tests.rs

@@ -747,7 +747,7 @@ async fn test_leave_group() -> Result<()> {
 
     assert_eq!(get_chat_contacts(&alice, alice_chat_id).await?.len(), 1);
 
-    assert_eq!(rcvd_leave_msg.state, MessageState::InSeen);
+    assert_eq!(rcvd_leave_msg.state, MessageState::InNoticed);
 
     alice.emit_event(EventType::Test);
     alice

src/imap.rs

@@ -1281,6 +1281,9 @@ impl Session {
             context.on_archived_chats_maybe_noticed();
         }
         for updated_chat_id in updated_chat_ids {
+            // NB: There are no other events that remove notifications at least for messages seen on
+            // other devices, so while we may also remove useful notifications for newer messages,
+            // we have no other choice.
             context.emit_event(EventType::MsgsNoticed(updated_chat_id));
             chatlist_events::emit_chatlist_item_changed(context, updated_chat_id);
         }

src/reaction.rs

@@ -525,6 +525,7 @@ Content-Disposition: reaction\n\
         assert_eq!(bob_reaction.as_str(), "👍");
 
         // Alice receives reaction to her message from Bob with a footer.
+        alice.evtracker.clear_events();
         receive_imf(
             &alice,
             "To: alice@example.org\n\
@@ -546,7 +547,11 @@ Here's my footer -- bob@example.net"
             false,
         )
         .await?;
-
+        let ev = alice
+            .evtracker
+            .get_matching_opt(&alice, |e| matches!(e, EventType::MsgsNoticed { .. }))
+            .await;
+        assert!(ev.is_none());
         let reactions = get_msg_reactions(&alice, msg.id).await?;
         assert_eq!(reactions.to_string(), "😀1");
 
@@ -590,6 +595,32 @@ Content-Disposition: reaction\n\
         let reactions = get_msg_reactions(&alice, msg.id).await?;
         assert_eq!(reactions.to_string(), "👍1");
 
+        // Alice receives a seen reaction to her message from Bob. If a reaction is seen, that's a
+        // result of an explicit user action and also means that the user has noticed notifications
+        // for earlier messages.
+        alice.evtracker.clear_events();
+        let seen = true;
+        receive_imf(
+            &alice,
+            "To: alice@example.org\n\
+From: bob@example.net\n\
+Date: Today, 29 February 2021 00:00:10 -800\n\
+Message-ID: 56792@example.net\n\
+In-Reply-To: 12345@example.org\n\
+Subject: Meeting\n\
+Mime-Version: 1.0 (1.0)\n\
+Content-Type: text/plain; charset=utf-8\n\
+Content-Disposition: reaction\n\
+\n\
+\u{1F44D}"
+                .as_bytes(),
+            seen,
+        )
+        .await?;
+        let _ev = alice
+            .evtracker
+            .get_matching(|e| matches!(e, EventType::MsgsNoticed { .. }))
+            .await;
         Ok(())
     }
 

src/receive_imf.rs

@@ -1014,6 +1014,9 @@ pub(crate) async fn receive_imf_inner(
             chat_id.emit_msg_event(context, *msg_id, mime_parser.incoming && fresh);
         }
     }
+    if !chat_id.is_trash() && received_msg.state == MessageState::InSeen {
+        context.emit_event(EventType::MsgsNoticed(chat_id));
+    }
     context.new_msgs_notify.notify_one();
 
     mime_parser
@@ -1751,10 +1754,12 @@ async fn add_parts(
 
     let state = if !mime_parser.incoming {
         MessageState::OutDelivered
-    } else if seen || is_mdn || chat_id_blocked == Blocked::Yes || group_changes.silent
+    } else if seen || is_mdn
     // No check for `hidden` because only reactions are such and they should be `InFresh`.
     {
         MessageState::InSeen
+    } else if chat_id_blocked == Blocked::Yes || group_changes.silent {
+        MessageState::InNoticed
     } else {
         MessageState::InFresh
     };

src/receive_imf/receive_imf_tests.rs

@@ -271,6 +271,31 @@ async fn test_adhoc_groups_merge() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_msgs_noticed_on_seen_msg() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let seen = true;
+    let rcvd_msg = receive_imf(
+        alice,
+        b"From: bob@example.net\n\
+        To: alice@example.org\n\
+        Message-ID: <3333@example.net>\n\
+        Date: Sun, 22 Mar 2020 22:37:57 +0000\n\
+        \n\
+        This is a seen message.\n",
+        seen,
+    )
+    .await?
+    .unwrap();
+    let ev = alice
+        .evtracker
+        .get_matching(|e| matches!(e, EventType::MsgsNoticed { .. }))
+        .await;
+    assert_eq!(ev, EventType::MsgsNoticed(rcvd_msg.chat_id));
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_mdn_and_alias() -> Result<()> {
     let mut tcm = TestContextManager::new();
@@ -2687,6 +2712,35 @@ async fn test_read_receipts_dont_unmark_bots() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_no_msgs_noticed_on_seen_mdn() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+
+    let received_msg = tcm.send_recv_accept(alice, bob, "hi").await;
+
+    let mdn_mimefactory = crate::mimefactory::MimeFactory::from_mdn(
+        bob,
+        received_msg.from_id,
+        received_msg.rfc724_mid,
+        vec![],
+    )
+    .await?;
+    let rendered_mdn = mdn_mimefactory.render(bob).await?;
+    let mdn_body = rendered_mdn.message;
+
+    let seen = true;
+    alice.evtracker.clear_events();
+    receive_imf(alice, mdn_body.as_bytes(), seen).await?;
+    let ev = alice
+        .evtracker
+        .get_matching_opt(alice, |e| matches!(e, EventType::MsgsNoticed { .. }))
+        .await;
+    assert!(ev.is_none());
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_gmx_forwarded_msg() -> Result<()> {
     let t = TestContext::new_alice().await;