Harden multi-user activity fetching

app/main.py

@@ -125,22 +125,47 @@ async def _fetch_source_usernames(
     if not usernames:
         return {}, False
 
-    cache_usernames = hashlib.sha1(",".join(sorted(usernames)).encode("utf-8")).hexdigest()[:12]
-    fetch_tasks: list[asyncio.Task[tuple[dict[str, int], bool]]] = []
+    fetch_tasks: list[asyncio.Task[tuple[str, tuple[dict[str, int], bool] | Exception]]] = []
     for username in usernames:
-        key = f"{source_prefix}_{cache_usernames}_{username}_{from_date}_{to_date}"
-        fetch_tasks.append(asyncio.create_task(_fetch_with_cache(cache, key, fetcher_factory(username))))
+        key = f"{source_prefix}_{username}_{from_date}_{to_date}"
+        fetch_tasks.append(
+            asyncio.create_task(
+                _fetch_source_username(cache, key, username, fetcher_factory(username))
+            )
+        )
 
     combined: dict[str, int] = {}
     stale = False
-    for data, entry_stale in await asyncio.gather(*fetch_tasks):
+    failures: list[Exception] = []
+    for username, result in await asyncio.gather(*fetch_tasks):
+        if isinstance(result, Exception):
+            logger.warning("source fetch failed for %s/%s, skipping user: %s", source_prefix, username, result)
+            failures.append(result)
+            continue
+
+        data, entry_stale = result
         stale = stale or entry_stale
         for day, count in data.items():
             combined[day] = combined.get(day, 0) + int(count)
 
+    if not combined and failures:
+        raise failures[0]
+
     return combined, stale
 
 
+async def _fetch_source_username(
+    cache: FileCache | None,
+    key: str,
+    username: str,
+    fetcher,
+) -> tuple[str, tuple[dict[str, int], bool] | Exception]:
+    try:
+        return username, await _fetch_with_cache(cache, key, fetcher)
+    except Exception as exc:
+        return username, exc
+
+
 async def collect_merged_activity(
     settings: Settings,
     cache: FileCache | None,

tests/test_main.py

@@ -1,9 +1,13 @@
+import tempfile
 from datetime import date
+from pathlib import Path
 
 import pytest
 
-from app.main import QueryOptions, collect_merged_activity
+from app.main import QueryOptions, collect_merged_activity, _fetch_source_usernames
+from app.cache import FileCache
 from app.settings import Settings
+from app.sources import github as github_source
 
 
 @pytest.mark.asyncio
@@ -38,3 +42,65 @@ async def test_collect_merged_activity_combines_multiple_usernames(monkeypatch)
     assert sorted(github_calls) == ["hubot", "octocat"]
     assert sorted(gitea_calls) == ["alice", "bob"]
     assert result.merged["2026-01-01"] == {"github": 3, "gitea": 7, "total": 10}
+
+
+@pytest.mark.asyncio
+async def test_fetch_source_usernames_skips_failed_accounts() -> None:
+    async def ok_fetch():
+        return {"2026-01-01": 2}
+
+    async def bad_fetch():
+        raise github_source.GitHubSourceError("boom")
+
+    result, stale = await _fetch_source_usernames(
+        None,
+        "github",
+        ["octocat", "hubot"],
+        date(2026, 1, 1),
+        date(2026, 1, 1),
+        lambda username: ok_fetch if username == "octocat" else bad_fetch,
+    )
+
+    assert result == {"2026-01-01": 2}
+    assert stale is False
+
+
+@pytest.mark.asyncio
+async def test_fetch_source_usernames_keeps_cache_after_username_list_changes() -> None:
+    with tempfile.TemporaryDirectory(dir=Path.cwd()) as temp_dir:
+        cache = FileCache(cache_dir=temp_dir, default_ttl_seconds=0)
+
+        def prime_fetcher(username):
+            async def fetch():
+                return {"2026-01-01": 1}
+
+            return fetch
+
+        await _fetch_source_usernames(
+            cache,
+            "github",
+            ["octocat"],
+            date(2026, 1, 1),
+            date(2026, 1, 1),
+            prime_fetcher,
+        )
+
+        def fetch_after_change(username):
+            async def fetch():
+                if username == "octocat":
+                    raise github_source.GitHubSourceError("down")
+                return {"2026-01-01": 2}
+
+            return fetch
+
+        result, stale = await _fetch_source_usernames(
+            cache,
+            "github",
+            ["octocat", "hubot"],
+            date(2026, 1, 1),
+            date(2026, 1, 1),
+            fetch_after_change,
+        )
+
+        assert result == {"2026-01-01": 3}
+        assert stale is True