fix: preserve unloaded sessions before replacement (#4190)

refs #4125

2 files changed, 24 insertions, 11 deletions

diff --git a/src/app/mod.rs b/src/app/mod.rs
index 4ac109c7..757a7f66 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -138,6 +138,7 @@ pub struct App {
     pub(crate) pending_agent_resume_deadline: Option<Instant>,
     pub(crate) session_save_deadline: Option<Instant>,
     pub(crate) session_save_thread: Option<std::thread::JoinHandle<()>>,
+    session_writer: Arc<std::sync::Mutex<crate::persist::SessionWriter>>,
     pane_exit_checkpoint_pending: bool,
     pub(crate) detached_process_children: Vec<std::process::Child>,
     tab_bar_status_generation: u64,
@@ -370,9 +371,11 @@ impl App {
         // Try to restore previous session
         let mut restored_terminals = std::collections::HashMap::new();
         let mut restored_terminal_runtimes = crate::terminal::TerminalRuntimeRegistry::new();
-        let (workspaces, active, selected) = if !policy.restore_session {
-            (Vec::new(), None, 0)
-        } else if let Some(snap) = crate::persist::load() {
+        let snapshot = policy.restore_session.then(crate::persist::load).flatten();
+        let session_writer = Arc::new(std::sync::Mutex::new(crate::persist::SessionWriter::new(
+            policy.restore_session && snapshot.is_none(),
+        )));
+        let (workspaces, active, selected) = if let Some(snap) = snapshot {
             let history = config
                 .experimental
                 .pane_history
@@ -599,6 +602,7 @@ impl App {
             pending_agent_resume_deadline: None,
             session_save_deadline: None,
             session_save_thread: None,
+            session_writer,
             pane_exit_checkpoint_pending: false,
             detached_process_children: Vec::new(),
             tab_bar_status_generation: 0,
diff --git a/src/app/session.rs b/src/app/session.rs
index 49dca914..08c4cd44 100644
--- a/src/app/session.rs
+++ b/src/app/session.rs
@@ -70,14 +70,15 @@ impl App {
         let job = self.capture_session_save_job();
         self.pane_exit_checkpoint_pending = false;
         self.session_save_deadline = None;
+        let writer = self.session_writer.clone();
         match std::thread::Builder::new()
             .name("herdr-session-save".into())
-            .spawn(move || run_session_save_job(job))
+            .spawn(move || run_session_save_job(job, &writer))
         {
             Ok(thread) => self.session_save_thread = Some(thread),
             Err(err) => {
                 tracing::warn!(err = %err, "failed to spawn session save thread; saving inline");
-                run_session_save_job(self.capture_session_save_job());
+                run_session_save_job(self.capture_session_save_job(), &self.session_writer);
             }
         }
     }
@@ -92,7 +93,7 @@ impl App {
             return;
         }
 
-        run_session_save_job(self.capture_session_save_job());
+        run_session_save_job(self.capture_session_save_job(), &self.session_writer);
         self.pane_exit_checkpoint_pending = false;
         self.session_save_deadline = None;
     }
@@ -124,11 +125,19 @@ impl App {
     }
 }
 
-fn run_session_save_job(job: SessionSaveJob) {
-    match job {
-        SessionSaveJob::Clear => crate::persist::clear(),
-        SessionSaveJob::Save { snapshot, history } => {
-            crate::persist::save(&snapshot, history.as_ref());
+fn run_session_save_job(
+    job: SessionSaveJob,
+    writer: &std::sync::Mutex<crate::persist::SessionWriter>,
+) {
+    let mut writer = match writer.lock() {
+        Ok(writer) => writer,
+        Err(err) => {
+            tracing::warn!(err = %err, "session writer is poisoned; refusing to modify session");
+            return;
         }
+    };
+    match job {
+        SessionSaveJob::Clear => writer.clear(),
+        SessionSaveJob::Save { snapshot, history } => writer.save(&snapshot, history.as_ref()),
     }
 }