feat: retain live snapshots while revalidating (#139)

tests/test_live_snapshot.py

@@ -9,8 +9,12 @@ from src import main
 @pytest.fixture(autouse=True)
 def reset_live_snapshot_task():
     main._live_snapshot_task = None
+    main._live_snapshot_value = None
+    main._live_snapshot_created_at = None
     yield
     main._live_snapshot_task = None
+    main._live_snapshot_value = None
+    main._live_snapshot_created_at = None
 
 
 def payload(response):
@@ -147,7 +151,7 @@ async def test_live_snapshot_keeps_fresh_activity_when_work_fails(monkeypatch):
 
 
 @pytest.mark.anyio
-async def test_live_snapshot_coalesces_only_simultaneous_requests(monkeypatch):
+async def test_live_snapshot_reuses_completed_snapshot_inside_freshness_window(monkeypatch):
     user_calls = 0
     release = asyncio.Event()
 
@@ -183,7 +187,47 @@ async def test_live_snapshot_coalesces_only_simultaneous_requests(monkeypatch):
     await asyncio.gather(first, second)
     await main.live_snapshot()
 
-    assert user_calls == 2
+    assert user_calls == 1
+
+
+@pytest.mark.anyio
+async def test_stale_snapshot_returns_immediately_while_one_refresh_revalidates(monkeypatch):
+    now = 100.0
+    refresh_started = asyncio.Event()
+    release_refresh = asyncio.Event()
+    builds = 0
+
+    async def snapshot():
+        nonlocal builds
+        builds += 1
+        if builds == 2:
+            refresh_started.set()
+            await release_refresh.wait()
+        return {
+            "context": {"generation": builds},
+            "events": [],
+            "notifications": [],
+            "sections": {},
+        }
+
+    monkeypatch.setattr(main.time, "monotonic", lambda: now)
+    monkeypatch.setattr(main, "_build_live_snapshot", snapshot)
+
+    first = payload(await main.live_snapshot())
+    now += main.LIVE_SNAPSHOT_FRESHNESS_SECONDS + 1
+    stale_request = asyncio.create_task(main.live_snapshot())
+    await refresh_started.wait()
+    await asyncio.sleep(0)
+    returned_immediately = stale_request.done()
+    release_refresh.set()
+    stale = payload(await stale_request)
+
+    assert returned_immediately is True
+    assert first["context"]["generation"] == 1
+    assert stale["context"]["generation"] == 1
+    assert stale["freshness"]["stale"] is True
+    assert stale["freshness"]["revalidating"] is True
+    assert builds == 2
 
 
 @pytest.mark.anyio

tests/test_notification_read.py

@@ -1,3 +1,5 @@
+import asyncio
+
 import httpx
 import pytest
 
@@ -45,3 +47,62 @@ async def test_mark_notification_read_api_is_bounded_and_never_cacheable(monkeyp
     assert response.headers["cache-control"] == "no-store"
     assert invalid.status_code == 422
     assert marked == [42]
+
+
+@pytest.mark.anyio
+async def test_mark_notification_read_removes_thread_from_retained_live_snapshot(monkeypatch):
+    async def mark(_thread_id):
+        return None
+
+    monkeypatch.setattr(main, "mark_notification_read", mark)
+    monkeypatch.setattr(
+        main,
+        "_live_snapshot_value",
+        {
+            "context": {},
+            "events": [],
+            "notifications": [{"id": 42}, {"id": 43}],
+            "sections": {"notifications": "fresh"},
+        },
+    )
+
+    response = await main.read_notification(42)
+
+    assert response.status_code == 200
+    assert main._live_snapshot_value is not None
+    assert main._live_snapshot_value["notifications"] == [{"id": 43}]
+
+
+@pytest.mark.anyio
+async def test_inflight_refresh_cannot_restore_a_notification_marked_read(monkeypatch):
+    refresh_started = asyncio.Event()
+    release_refresh = asyncio.Event()
+
+    async def mark(_thread_id):
+        return None
+
+    async def stale_upstream_snapshot():
+        refresh_started.set()
+        await release_refresh.wait()
+        return {
+            "context": {},
+            "events": [],
+            "notifications": [{"id": 42}, {"id": 43}],
+            "sections": {"notifications": "fresh"},
+        }
+
+    monkeypatch.setattr(main, "mark_notification_read", mark)
+    monkeypatch.setattr(
+        main, "_build_live_snapshot_before_deadline", stale_upstream_snapshot
+    )
+    monkeypatch.setattr(main, "_live_snapshot_task", None)
+    monkeypatch.setattr(main, "_live_snapshot_value", {"notifications": [{"id": 42}]})
+
+    refresh = main._start_live_snapshot_refresh()
+    await refresh_started.wait()
+    await main.read_notification(42)
+    release_refresh.set()
+    await refresh
+
+    assert main._live_snapshot_value is not None
+    assert main._live_snapshot_value["notifications"] == [{"id": 43}]

tests/test_shared_context_snapshot.py

@@ -26,4 +26,12 @@ async def test_one_live_snapshot_updates_work_and_activity_on_one_timer():
     assert "renderContextSnapshot(snapshot.context)" in html
     assert "paintEventStream(snapshot.events)" in html
     assert "loadEventStream" not in html
-    assert "5000" not in html
+    assert "5000" not in html
+
+
+@pytest.mark.anyio
+async def test_dashboard_announces_when_recent_snapshot_is_revalidating():
+    html = await dashboard()
+
+    assert "snapshot.freshness?.revalidating" in html
+    assert "Refreshing · showing recent snapshot" in html