fix(system): answer a failed System read only after its other reads finish

CI (py3.10 on ubuntu) crashed with a segfault inside SQLite in
test_statistics_failure_is_an_error_envelope: the statistics and overview
routes used asyncio.gather without return_exceptions, so the 500 answered
on the first failure while get_statistics still ran in the executor, and
the test tore the database down under it. Both routes now await every
read before raising the first failure (failing before, passing after:
TestFailedReadsSettleFirst).

The frontend coverage merge failed on workspace/activity.mjs branches
(86.3 < 87): no test asserted Activity's empty and failed-read states, so
their branch was only reached in passing, depending on timing. A spec now
asserts both.

py/api/system.py

@@ -40,6 +40,19 @@ _HEALTH_STATUS_LINES = {
 _StoredReport = namedtuple("_StoredReport", "generation report")
 
 
+async def _gather_settled(*reads):
+    """Await every read, then raise the first failure.
+
+    Unlike a plain gather, a failure never answers while the other executor
+    reads still run against the database.
+    """
+    results = await asyncio.gather(*reads, return_exceptions=True)
+    for result in results:
+        if isinstance(result, BaseException):
+            raise result
+    return results
+
+
 def _failure(message, status=500, code=None):
     return web.json_response(
         {"success": False, "code": code, "error": message}, status=status
@@ -154,7 +167,7 @@ class SystemRoutesMixin:
         from ..config import GalleryConfig
 
         try:
-            (output_dirs, auto_detected), counts = await asyncio.gather(
+            (output_dirs, auto_detected), counts = await _gather_settled(
                 self._run_in_executor(self._output_dirs_with_origin),
                 self._run_in_executor(self.db.library_counts),
             )
@@ -188,7 +201,7 @@ class SystemRoutesMixin:
 
     async def get_system_statistics(self, request):
         try:
-            by_category, totals, counts = await asyncio.gather(
+            by_category, totals, counts = await _gather_settled(
                 self._run_in_executor(self.db.usage_by_category),
                 self._run_in_executor(self.db.get_statistics),
                 self._run_in_executor(self.db.library_counts),

tests/browser/workspace-activity.spec.mjs

@@ -284,6 +284,19 @@ test('reload during a scan reattaches to the running job', async ({ page, reques
     await expect(pill(page)).toBeHidden();
 });
 
+test('an empty Activity says no job has run, and a list that cannot be read says so', async ({ page }) => {
+    // The empty and failed states were only reached in passing by other tests, so their coverage depended on timing.
+    const empty = main(page).locator('section.surface > p.empty-state');
+    await page.goto(`${workspace}#/activity`);
+    await expect(empty).toHaveText('No jobs have run since ComfyUI started. Scans and other long operations appear here.');
+    await expect(empty).not.toHaveAttribute('role');
+    await expect(items(page)).toHaveCount(0);
+    await page.route(url => url.pathname === '/prompt_manager/jobs', route => route.abort());
+    await page.reload();
+    await expect(empty).toHaveText('Activity could not be read. It is tried again shortly.');
+    await expect(empty).toHaveAttribute('role', 'alert');
+});
+
 test('lost server clears the pill and marks jobs ended', async ({ page, request }) => {
     // A poll interval after the restart, then failed re-reads backing off for 1 + 2 + 4 s.
     test.setTimeout(90_000);

tests/test_system_api.py

@@ -416,6 +416,63 @@ class TestStatisticsRoute(SystemAPITestCase):
         )
 
 
+class TestFailedReadsSettleFirst(SystemAPITestCase):
+    """A failed read answers only after the route's other reads finished.
+
+    Answering on the first failure (``asyncio.gather`` without
+    ``return_exceptions``) left the other executor reads running against a
+    database the caller may already be closing; on Python 3.10 CI that
+    crashed the test process inside SQLite.
+    """
+
+    async def assert_answers_after_reads(self, url, failing, slow, error):
+        raised, release, finished = (threading.Event() for _ in range(3))
+        real = getattr(*slow)
+
+        def fail(*args, **kwargs):
+            raised.set()
+            raise RuntimeError("secret")
+
+        def held(*args, **kwargs):
+            release.wait()
+            try:
+                return real(*args, **kwargs)
+            finally:
+                finished.set()
+
+        with (
+            patch.object(*failing, side_effect=fail),
+            patch.object(*slow, side_effect=held),
+            self.assertLogs("prompt_manager.api", "ERROR"),
+        ):
+            answer = asyncio.ensure_future(self.json("GET", url, 500))
+            try:
+                await asyncio.get_running_loop().run_in_executor(None, raised.wait)
+                done, _ = await asyncio.wait({answer}, timeout=0.5)
+                self.assertEqual(done, set(), "answered while a read still ran")
+            finally:
+                release.set()
+            body = await answer
+        self.assertTrue(finished.is_set())
+        self.assertEqual(body, {"success": False, "code": None, "error": error})
+
+    async def test_statistics(self):
+        await self.assert_answers_after_reads(
+            "/prompt_manager/system/statistics",
+            (self.api.db, "usage_by_category"),
+            (self.api.db, "get_statistics"),
+            "Failed to read statistics",
+        )
+
+    async def test_overview(self):
+        await self.assert_answers_after_reads(
+            "/prompt_manager/system/overview",
+            (self.api.db, "library_counts"),
+            (self.api, "_output_dirs_with_origin"),
+            "Failed to read the overview",
+        )
+
+
 if __name__ == "__main__":
     import unittest