perf: skip unchanged live snapshot sections (#285)

tests/test_context_polling.py

@@ -63,3 +63,54 @@ const poller = createContextPoller({{
         "callsWhileHidden": 1,
         "callsAfterResume": 2,
     }
+
+
+def test_context_poller_sends_revisions_and_merges_changed_sections():
+    script = f"""
+const createContextPoller = require({json.dumps(str(POLLER))});
+const requested = [];
+const rendered = [];
+const responses = [
+  {{ context: {{ user: {{ login: 'timmy' }} }}, events: [{{ id: 1 }}], notifications: [],
+     sections: {{ context: 'fresh', events: 'fresh', notifications: 'fresh' }},
+     revisions: {{ context: 1, events: 1, notifications: 1 }}, freshness: {{ age_seconds: 0 }} }},
+  {{ sections: {{ context: 'fresh', events: 'fresh', notifications: 'fresh' }},
+     revisions: {{ context: 1, events: 2, notifications: 1 }}, events: [{{ id: 2 }}],
+     freshness: {{ age_seconds: 1 }} }},
+  {{ sections: {{ context: 'fresh', events: 'fresh', notifications: 'fresh' }},
+     revisions: {{ context: 1, events: 2, notifications: 1 }}, freshness: {{ age_seconds: 2 }} }},
+];
+const poller = createContextPoller({{
+  fetchContext: revisions => {{ requested.push({{ ...revisions }}); return Promise.resolve(responses.shift()); }},
+  onSnapshot: (snapshot, changed) => rendered.push({{
+    context: snapshot.context.user.login,
+    event: snapshot.events[0].id,
+    age: snapshot.freshness.age_seconds,
+    changed,
+  }}),
+  onError: error => {{ throw error; }},
+  setTimer: () => 1,
+  clearTimer: () => {{}},
+}});
+(async () => {{
+  await poller.refresh();
+  await poller.refresh();
+  await poller.refresh();
+  process.stdout.write(JSON.stringify({{ requested, rendered }}));
+}})();
+"""
+
+    assert run_node(script) == {
+        "requested": [
+            {},
+            {"context": 1, "events": 1, "notifications": 1},
+            {"context": 1, "events": 2, "notifications": 1},
+        ],
+        "rendered": [
+            {"context": "timmy", "event": 1, "age": 0,
+             "changed": ["context", "events", "notifications"]},
+            {"context": "timmy", "event": 2, "age": 1,
+             "changed": ["events"]},
+            {"context": "timmy", "event": 2, "age": 2, "changed": []},
+        ],
+    }

tests/test_live_snapshot.py

@@ -21,6 +21,9 @@ def reset_live_snapshot_task():
         section: None for section in main.LIVE_SNAPSHOT_SECTIONS
     }
     main._live_snapshot_refreshing_sections = set()
+    main._live_section_revisions = {
+        section: 0 for section in main.LIVE_SNAPSHOT_SECTIONS
+    }
     yield
     main._live_snapshot_task = None
     main._live_snapshot_value = None
@@ -35,6 +38,9 @@ def reset_live_snapshot_task():
         section: None for section in main.LIVE_SNAPSHOT_SECTIONS
     }
     main._live_snapshot_refreshing_sections = set()
+    main._live_section_revisions = {
+        section: 0 for section in main.LIVE_SNAPSHOT_SECTIONS
+    }
 
 
 def payload(response):
@@ -84,6 +90,43 @@ async def test_live_snapshot_fetches_user_once_and_updates_work_and_activity(mon
     assert result["sections"] == {
         "context": "fresh", "events": "fresh", "notifications": "fresh"
     }
+    assert result["revisions"] == {
+        "context": 1, "events": 1, "notifications": 1
+    }
+
+
+@pytest.mark.anyio
+async def test_live_snapshot_omits_section_bodies_at_known_revisions(monkeypatch):
+    async def user():
+        return {"id": 1, "login": "timmy"}
+
+    async def empty():
+        return []
+
+    async def events(_authenticated_user):
+        return [{"type": "push"}]
+
+    monkeypatch.setattr(main, "current_user", user)
+    monkeypatch.setattr(main, "repos", empty)
+    monkeypatch.setattr(main, "issues", empty)
+    monkeypatch.setattr(main, "pull_requests", empty)
+    monkeypatch.setattr(main, "activity_events", events)
+    monkeypatch.setattr(main, "notifications", empty)
+
+    first = payload(await main.live_snapshot())
+    second = payload(await main.live_snapshot(
+        context_revision=first["revisions"]["context"],
+        events_revision=first["revisions"]["events"],
+        notifications_revision=first["revisions"]["notifications"],
+    ))
+
+    assert "context" not in second
+    assert "events" not in second
+    assert "notifications" not in second
+    assert "notification_pagination" not in second
+    assert second["sections"] == first["sections"]
+    assert second["revisions"] == first["revisions"]
+    assert "freshness" in second
 
 
 @pytest.mark.anyio

tests/test_offline_work.py

@@ -112,4 +112,5 @@ async def test_initial_http_outage_hydrates_saved_work_and_recovers_on_live_snap
     assert "Outage · saved " in html
     assert "Server unavailable · showing private My Work saved " in html
     assert "Live details and actions will return automatically." in html
-    assert "function renderLiveSnapshot(snapshot) {\n    setOfflineWorkMode(false);\n    offlineStatus.hidden = true;" in html
+    assert "function renderLiveSnapshot(snapshot, changedSections" in html
+    assert "setOfflineWorkMode(false);\n    offlineStatus.hidden = true;" in html

tests/test_service_worker.py

@@ -91,10 +91,10 @@ async function dispatchNotificationClick(route) {{
     return json.loads(completed.stdout)
 
 
-def test_edited_issue_retry_ships_in_a_new_shell_cache():
+def test_live_section_revisions_ship_in_a_new_shell_cache():
     source = WORKER.read_text()
 
-    assert "stackchain-dashboard-shell-v22" in source
+    assert "stackchain-dashboard-shell-v23" in source
     assert "BASE + 'static/today-work.js'" in source
 
 

tests/test_shared_context_snapshot.py

@@ -22,7 +22,9 @@ async def test_one_live_snapshot_updates_work_and_activity_on_one_timer():
     html = await dashboard()
 
     assert "fetch('api/v1/live'" in html
-    assert "renderLiveSnapshot(snapshot)" in html
+    assert "onSnapshot: renderLiveSnapshot" in html
+    assert "section + '_revision'" in html
+    assert "workChanged = contextChanged || notificationsChanged" in html
     assert "renderContextSnapshot(snapshot.context)" in html
     assert "paintEventStream(snapshot.events)" in html
     assert "loadEventStream" not in html