feat: Remove subject prefix from ad-hoc group names (#5385)

Delta Chat -style groups have names w/o prefixes like "Re: " even if the user is added to an already
existing group, so let's remove prefixes from ad-hoc group names too. Usually it's not very
important that the group is a classic email thread existed before, this info just eats up screen
space. Also this way a group name is likely to preserve if the first message was missed.

src/receive_imf.rs

@@ -40,7 +40,7 @@ use crate::simplify;
 use crate::sql;
 use crate::stock_str;
 use crate::sync::Sync::*;
-use crate::tools::{self, buf_compress};
+use crate::tools::{self, buf_compress, remove_subject_prefix};
 use crate::{chatlist_events, location};
 use crate::{contact, imap};
 use iroh_net::NodeAddr;
@@ -1936,8 +1936,9 @@ async fn create_group(
  let grpname = mime_parser
  .get_header(HeaderDef::ChatGroupName)
  .context("Chat-Group-Name vanished")?
- // W/a for "Space added before long group names after MIME serialization/deserialization
- // #3650" issue. DC itself never creates group names with leading/trailing whitespace.
+ // Workaround for the "Space added before long group names after MIME
+ // serialization/deserialization #3650" issue. DC itself never creates group names with
+ // leading/trailing whitespace.
  .trim();
  let new_chat_id = ChatId::create_multiuser_record(
  context,
@@ -2127,12 +2128,10 @@ async fn apply_group_changes(
  }
  } else if let Some(old_name) = mime_parser
  .get_header(HeaderDef::ChatGroupNameChanged)
- // See create_or_lookup_group() for explanation
  .map(|s| s.trim())
  {
  if let Some(grpname) = mime_parser
  .get_header(HeaderDef::ChatGroupName)
- // See create_or_lookup_group() for explanation
  .map(|grpname| grpname.trim())
  .filter(|grpname| grpname.len() < 200)
  {
@@ -2547,9 +2546,9 @@ async fn create_adhoc_group(
  return Ok(None);
  }
 
- // use subject as initial chat name
  let grpname = mime_parser
  .get_subject()
+ .map(|s| remove_subject_prefix(&s))
  .unwrap_or_else(|| "Unnamed group".to_string());
 
  let new_chat_id: ChatId = ChatId::create_multiuser_record(

src/receive_imf/tests.rs

@@ -4228,6 +4228,33 @@ async fn test_keep_member_list_if_possibly_nomember() -> Result<()> {
  Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_adhoc_grp_name_no_prefix() -> Result<()> {
+ let mut tcm = TestContextManager::new();
+ let alice = &tcm.alice().await;
+ let chat_id = receive_imf(
+ alice,
+ b"Subject: Re: Once upon a time this was with the only Re: here\n\
+ From: <[email protected]>\n\
+ To: <[email protected]>, <[email protected]>\n\
+ Date: Mon, 12 Dec 3000 14:32:39 +0000\n\
+ Message-ID: <[email protected]>\n\
+ In-Reply-To: <[email protected]>\n\
+ \n\
+ Adding Alice the Delta Chat lover",
+ false,
+ )
+ .await?
+ .unwrap()
+ .chat_id;
+ let chat = Chat::load_from_db(alice, chat_id).await.unwrap();
+ assert_eq!(
+ chat.get_name(),
+ "Once upon a time this was with the only Re: here"
+ );
+ Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_download_later() -> Result<()> {
  let mut tcm = TestContextManager::new();