Suppress errors for requested session stops

server/src/session/mod.rs

@@ -1652,6 +1652,7 @@ impl SessionManager {
                 cwd.display(),
                 record.pid
             );
+            process::mark_stopping(&dir)?;
             process::stop(&record, process::STOP_GRACE);
         }
         Ok(())
@@ -1714,6 +1715,7 @@ impl SessionManager {
                 effort.unwrap_or("default"),
                 record.pid
             );
+            process::mark_stopping(&dir)?;
             process::stop(&record, process::STOP_GRACE);
         }
         Ok(())
@@ -1761,6 +1763,7 @@ impl SessionManager {
             }
         };
         tracing::info!("stopping session {id} (pid {})", record.pid);
+        process::mark_stopping(&self.data_dir.join(id))?;
         process::stop(&record, process::STOP_GRACE);
         Ok(())
     }
@@ -4329,6 +4332,52 @@ mod tests {
         ));
     }
 
+    /// Stderr is a log of the process's whole lifetime, not necessarily why it
+    /// ended. A requested Stop used to paste its oldest surviving diagnostics
+    /// into the transcript as a fresh failure -- complete with terminal escape
+    /// codes -- even though the process ended only because the person asked.
+    #[tokio::test]
+    async fn stopping_a_session_does_not_report_old_stderr_as_a_failure() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let config_path = dir.path().join("config.ron");
+        let data_dir = dir.path().join("sessions");
+        let provider = seed_stand_in_cli(&config_path, dir.path());
+        let manager = SessionManager::new(config_path, data_dir.clone(), data_dir.join("models"))
+            .expect("manager");
+        let info = manager
+            .spawn_session(stand_in_spec(&provider))
+            .expect("spawn");
+        let mut rx = manager.session(&info.id).expect("live").subscribe();
+        let session_dir = data_dir.join(&info.id);
+
+        std::fs::write(
+            session_dir.join("stderr.log"),
+            "\u{1b}[31mERROR\u{1b}[0m an old tool diagnostic\n",
+        )
+        .expect("seed stderr");
+        manager.stop_session(&info.id).expect("stop");
+
+        let seen = collect_until(&mut rx, |event| {
+            matches!(
+                event,
+                Event::Status {
+                    state: SessionStatus::Exited
+                }
+            )
+        })
+        .await;
+        assert!(
+            !seen
+                .iter()
+                .any(|entry| matches!(entry.event, Event::Error { .. })),
+            "a requested stop was presented as a failure: {seen:?}"
+        );
+        assert!(
+            !process::stopping(&session_dir),
+            "the completed stop left its marker behind"
+        );
+    }
+
     /// A message and a command both mean "now", so neither answers that the
     /// session's process has gone -- they start one and go to it.
     ///