fix: count recipients by Intended Recipient Fingerprints

Fixes <https://github.com/chatmail/core/issues/7987>

deltachat-rpc-client/tests/test_multitransport.py

@@ -1,7 +1,7 @@
 import pytest
 
 from deltachat_rpc_client import EventType
-from deltachat_rpc_client.const import DownloadState
+from deltachat_rpc_client.const import ChatType, DownloadState
 from deltachat_rpc_client.rpc import JsonRpcError
 
 
@@ -357,7 +357,7 @@ def test_message_info_imap_urls(acfactory) -> None:
     assert f"{new_alice_addr}/INBOX" in msg_info
 
 
-def test_remove_primary_transport(acfactory) -> None:
+def test_remove_primary_transport(acfactory, log) -> None:
     """Test that after removing the primary relay, Alice can still receive messages."""
     alice, bob = acfactory.get_online_accounts(2)
     qr = acfactory.get_account_qr()
@@ -368,7 +368,7 @@ def test_remove_primary_transport(acfactory) -> None:
     bob_chat = bob.create_chat(alice)
     alice.create_chat(bob)
 
-    # Alice changes the transport.
+    log.section("Alice sets up second transport")
     [transport1, transport2] = alice.list_transports()
     alice.set_config("configured_addr", transport2["addr"])
 
@@ -376,7 +376,7 @@ def test_remove_primary_transport(acfactory) -> None:
     msg1 = alice.wait_for_incoming_msg().get_snapshot()
     assert msg1.text == "Hello!"
 
-    # Alice deletes the first transport.
+    log.section("Alice removes the primary relay")
     alice.delete_transport(transport1["addr"])
     alice.stop_io()
     alice.start_io()
@@ -384,3 +384,5 @@ def test_remove_primary_transport(acfactory) -> None:
     bob_chat.send_text("Hello again!")
     msg2 = alice.wait_for_incoming_msg().get_snapshot()
     assert msg2.text == "Hello again!"
+    assert msg2.chat.get_basic_snapshot().chat_type == ChatType.SINGLE
+    assert msg2.chat == alice.create_chat(bob)

src/receive_imf.rs

@@ -1322,6 +1322,25 @@ async fn decide_chat_assignment(
     // no database row and ChatId yet.
     let mut num_recipients = 0;
     let mut has_self_addr = false;
+
+    if let Some((sender_fingerprint, intended_recipient_fingerprints)) = mime_parser
+        .signature
+        .as_ref()
+        .filter(|(_sender_fingerprint, fps)| !fps.is_empty())
+    {
+        // The message is signed and has intended recipient fingerprints.
+
+        // If the message has intended recipient fingerprint and is not trashed already,
+        // then it is intended for us.
+        has_self_addr = true;
+
+        num_recipients = intended_recipient_fingerprints
+            .iter()
+            .filter(|fp| *fp != sender_fingerprint)
+            .count();
+    } else {
+        // Message has no intended recipient fingerprints
+        // or is not signed, count the `To` field recipients.
         for recipient in &mime_parser.recipients {
             has_self_addr |= context.is_self_addr(&recipient.addr).await?;
             if addr_cmp(&recipient.addr, &mime_parser.from.addr) {
@@ -1332,6 +1351,7 @@ async fn decide_chat_assignment(
         if from_id != ContactId::SELF && !has_self_addr {
             num_recipients += 1;
         }
+    }
     let mut can_be_11_chat_log = String::new();
     let mut l = |cond: bool, s: String| {
         can_be_11_chat_log += &s;