fix(tui): ignore a queued PinChanged once the thread is gone

src/pepper_cli/tui/app.py

@@ -1556,6 +1556,10 @@ def on_thread_view_at_top(self, _event: ThreadView.AtTop) -> None:
     def on_thread_view_pin_changed(self, _event: ThreadView.PinChanged) -> None:
         """Reached the end (the newest row is on screen, so it is read) or scrolled away from
         it (rows below are unseen: the open topic shows as unread)."""
+        if not self.query(ThreadView):
+            # A message queued as the app tears down is dispatched after the screen's widgets
+            # are gone; there is no thread left to read or mark (#139).
+            return
         self._note_viewed()
         self._run("publish")
         self.refresh_chrome()

tests/test_tui_live.py

@@ -18,6 +18,7 @@
 
 from pepper_cli.tui import app as tui_app
 from pepper_cli.tui import state, stream
+from pepper_cli.tui.thread import ThreadView
 from tests import tui_support as ts
 from tests.tui_support import body_text, until
 
@@ -292,6 +293,18 @@ async def test_nothing_is_marked_read_while_the_thread_is_scrolled_up(
         await until(pilot, lambda: (ts.TOPIC_A1, arrived) in server.puts)
 
 
+async def test_a_pin_change_delivered_after_the_thread_is_gone_is_ignored() -> None:
+    """The cue can be dispatched during teardown, once the thread is gone (#139): no crash."""
+    server = ts.standard_server()
+    app = tui_app.PepperApp(server.client())
+    async with app.run_test(size=(120, 20)) as pilot:
+        await until(pilot, lambda: len(app.rooms) == 2)
+        app.open_conversation(state.Conversation(ts.ROOM_A, ts.TOPIC_A1))
+        await until(pilot, lambda: app.loaded_topic)
+        await app.thread.remove()
+        app.on_thread_view_pin_changed(ThreadView.PinChanged(True))
+
+
 async def test_reaching_the_end_marks_the_newest_row_read(monkeypatch: pytest.MonkeyPatch) -> None:
     server = ts.standard_server()
     _long_topic(server)