fix: do not miss new messages while expunging the folder

This should fix flaky `test_verified_group_vs_delete_server_after`.

Author: link2xt

src/imap.rs

@@ -32,6 +32,7 @@ use crate::contact::{Contact, ContactId, Modifier, Origin};
 use crate::context::Context;
 use crate::events::EventType;
 use crate::headerdef::{HeaderDef, HeaderDefMap};
+use crate::imap::select_folder::NewlySelected;
 use crate::login_param::{CertificateChecks, LoginParam, ServerLoginParam};
 use crate::message::{self, Message, MessageState, MessengerMessage, MsgId, Viewtype};
 use crate::mimeparser;
@@ -548,10 +549,11 @@ impl Imap {
             .await
             .with_context(|| format!("Failed to select folder {folder:?}"))?;
 
-        if !new_emails && !fetch_existing_msgs {
+        if !session.should_fetch && !new_emails && !fetch_existing_msgs {
             info!(context, "No new emails in folder {folder:?}.");
             return Ok(false);
         }
+        session.should_fetch = false;
 
         let uid_validity = get_uidvalidity(context, folder).await?;
         let old_uid_next = get_uid_next(context, folder).await?;
@@ -1131,9 +1133,18 @@ impl Session {
             return Ok(());
         }
 
-        self.select_folder(context, folder)
+        if self
+            .select_folder(context, folder)
             .await
-            .context("failed to select folder")?;
+            .context("failed to select folder")?
+            == NewlySelected::Yes
+        {
+            info!(
+                context,
+                "Folder {folder} was unselected before, should fetch."
+            );
+            self.should_fetch = true;
+        }
 
         let mailbox = self
             .selected_mailbox

src/imap/idle.rs

@@ -31,7 +31,8 @@ impl Session {
 
         self.select_folder(context, folder).await?;
 
-        if self.server_sent_unsolicited_exists(context)? {
+        if self.server_sent_unsolicited_exists(context)? || self.should_fetch {
+            self.should_fetch = false;
             return Ok(self);
         }
 

src/imap/session.rs

@@ -40,6 +40,10 @@ pub(crate) struct Session {
     pub selected_mailbox: Option<Mailbox>,
 
     pub selected_folder_needs_expunge: bool,
+
+    /// Flag that is set to `true`
+    /// when we select a folder and detect that it has new messages.
+    pub should_fetch: bool,
 }
 
 impl Deref for Session {
@@ -67,6 +71,7 @@ impl Session {
             selected_folder: None,
             selected_mailbox: None,
             selected_folder_needs_expunge: false,
+            should_fetch: false,
         }
     }