From 44e3e886ca9cb5f1755254035917480345c520a6 Mon Sep 17 00:00:00 2001
From: stevejpurves <steve@curvenote.com>
Date: Wed, 22 Nov 2023 11:36:55 +0000
Subject: [PATCH] =?UTF-8?q?=E2=98=9D=F0=9F=8F=BCpromote=20session=20shutdo?=
 =?UTF-8?q?wn=20events=20to=20errors=20for=20thebe=20sessions?=
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---
 .changeset/tender-sloths-battle.md          |  5 +++++
 packages/react/src/ThebeSessionProvider.tsx | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 .changeset/tender-sloths-battle.md

diff --git a/.changeset/tender-sloths-battle.md b/.changeset/tender-sloths-battle.md
new file mode 100644
index 00000000..e1e50b8f
--- /dev/null
+++ b/.changeset/tender-sloths-battle.md
@@ -0,0 +1,5 @@
+---
+'thebe-react': patch
+---
+
+`ThebeSessionProvider` monitors status events for session/kernel shutdown messages and promotes this to an error if the corresponding session has shutdown.
diff --git a/packages/react/src/ThebeSessionProvider.tsx b/packages/react/src/ThebeSessionProvider.tsx
index 820bc0ef..da4916c7 100644
--- a/packages/react/src/ThebeSessionProvider.tsx
+++ b/packages/react/src/ThebeSessionProvider.tsx
@@ -2,6 +2,8 @@ import React, { useContext, useEffect, useState } from 'react';
 import type { ThebeSession } from 'thebe-core';
 import { useThebeServer } from './ThebeServerProvider';
 import { useRenderMimeRegistry } from './ThebeRenderMimeRegistryProvider';
+import { ThebeEventData } from 'thebe-core';
+import { useThebeLoader } from './ThebeLoaderProvider';
 
 interface ThebeSessionContextData {
   path?: string;
@@ -27,6 +29,7 @@ export function ThebeSessionProvider({
   path?: string;
   shutdownOnUnmount?: boolean;
 }>) {
+  const { core } = useThebeLoader();
   const { config, server, ready: serverReady } = useThebeServer();
   const rendermime = useRenderMimeRegistry();
 
@@ -42,6 +45,23 @@ export function ThebeSessionProvider({
     startSession();
   }, [ready, doStart, starting, server, serverReady]);
 
+  // register an event handler to monitor for session status changes
+  useEffect(() => {
+    if (!core || !config || !session) return;
+    const handler = (evt: string, data: ThebeEventData) => {
+      const subjects = [core.EventSubject.session, core.EventSubject.kernel];
+      if (
+        data.subject &&
+        subjects.includes(data.subject) &&
+        data.status === 'shutdown' &&
+        data.id === session.id
+      ) {
+        setError(`session ${path} - ${data.status} - ${data.message}`);
+      }
+    };
+    config.events.on(core.ThebeEventType.status, handler);
+  }, [core, config, session]);
+
   const startSession = () => {
     if (!rendermime) throw new Error('ThebeSessionProvider requires a RenderMimeRegistryProvider');
     setStarting(true);