Render error state when agent binary exits unexpectedly (#35651)

This PR adds handling for the case where an agent binary exits
unexpectedly after successfully establishing a connection.

Release Notes:

- N/A

---------

Co-authored-by: Agus <agus@zed.dev>

crates/agent_ui/src/acp/thread_view.rs

@@ -5,6 +5,7 @@ use audio::{Audio, Sound};
 use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::path::Path;
+use std::process::ExitStatus;
 use std::rc::Rc;
 use std::sync::Arc;
 use std::time::Duration;
@@ -90,6 +91,9 @@ enum ThreadState {
     Unauthenticated {
         connection: Rc<dyn AgentConnection>,
     },
+    ServerExited {
+        status: ExitStatus,
+    },
 }
 
 impl AcpThreadView {
@@ -229,7 +233,7 @@ impl AcpThreadView {
         let connect_task = agent.connect(&root_dir, &project, cx);
         let load_task = cx.spawn_in(window, async move |this, cx| {
             let connection = match connect_task.await {
-                Ok(thread) => thread,
+                Ok(connection) => connection,
                 Err(err) => {
                     this.update(cx, |this, cx| {
                         this.handle_load_error(err, cx);
@@ -240,6 +244,20 @@ impl AcpThreadView {
                 }
             };
 
+            // this.update_in(cx, |_this, _window, cx| {
+            //     let status = connection.exit_status(cx);
+            //     cx.spawn(async move |this, cx| {
+            //         let status = status.await.ok();
+            //         this.update(cx, |this, cx| {
+            //             this.thread_state = ThreadState::ServerExited { status };
+            //             cx.notify();
+            //         })
+            //         .ok();
+            //     })
+            //     .detach();
+            // })
+            // .ok();
+
             let result = match connection
                 .clone()
                 .new_thread(project.clone(), &root_dir, cx)
@@ -308,7 +326,8 @@ impl AcpThreadView {
             ThreadState::Ready { thread, .. } => Some(thread),
             ThreadState::Unauthenticated { .. }
             | ThreadState::Loading { .. }
-            | ThreadState::LoadError(..) => None,
+            | ThreadState::LoadError(..)
+            | ThreadState::ServerExited { .. } => None,
         }
     }
 
@@ -318,6 +337,7 @@ impl AcpThreadView {
             ThreadState::Loading { .. } => "Loading…".into(),
             ThreadState::LoadError(_) => "Failed to load".into(),
             ThreadState::Unauthenticated { .. } => "Not authenticated".into(),
+            ThreadState::ServerExited { .. } => "Server exited unexpectedly".into(),
         }
     }
 
@@ -647,6 +667,9 @@ impl AcpThreadView {
                     cx,
                 );
             }
+            AcpThreadEvent::ServerExited(status) => {
+                self.thread_state = ThreadState::ServerExited { status: *status };
+            }
         }
         cx.notify();
     }
@@ -1383,7 +1406,29 @@ impl AcpThreadView {
             .into_any()
     }
 
-    fn render_error_state(&self, e: &LoadError, cx: &Context<Self>) -> AnyElement {
+    fn render_server_exited(&self, status: ExitStatus, _cx: &Context<Self>) -> AnyElement {
+        v_flex()
+            .items_center()
+            .justify_center()
+            .child(self.render_error_agent_logo())
+            .child(
+                v_flex()
+                    .mt_4()
+                    .mb_2()
+                    .gap_0p5()
+                    .text_center()
+                    .items_center()
+                    .child(Headline::new("Server exited unexpectedly").size(HeadlineSize::Medium))
+                    .child(
+                        Label::new(format!("Exit status: {}", status.code().unwrap_or(-127)))
+                            .size(LabelSize::Small)
+                            .color(Color::Muted),
+                    ),
+            )
+            .into_any_element()
+    }
+
+    fn render_load_error(&self, e: &LoadError, cx: &Context<Self>) -> AnyElement {
         let mut container = v_flex()
             .items_center()
             .justify_center()
@@ -2494,7 +2539,13 @@ impl Render for AcpThreadView {
                     .flex_1()
                     .items_center()
                     .justify_center()
-                    .child(self.render_error_state(e, cx)),
+                    .child(self.render_load_error(e, cx)),
+                ThreadState::ServerExited { status } => v_flex()
+                    .p_2()
+                    .flex_1()
+                    .items_center()
+                    .justify_center()
+                    .child(self.render_server_exited(*status, cx)),
                 ThreadState::Ready { thread, .. } => {
                     let thread_clone = thread.clone();
 

crates/agent_ui/src/agent_diff.rs

@@ -1523,7 +1523,8 @@ impl AgentDiff {
             }
             AcpThreadEvent::Stopped
             | AcpThreadEvent::ToolAuthorizationRequired
-            | AcpThreadEvent::Error => {}
+            | AcpThreadEvent::Error
+            | AcpThreadEvent::ServerExited(_) => {}
         }
     }