fix: surface all calendar sync failures, not just Google

CalDAV and Home Assistant sync failures were previously only logged
server-side, leaving clients unable to distinguish an empty calendar
from a broken sync. Unify error reporting across CalDAV, Home
Assistant, and Google into a single errors list on GET
/api/caldav/events, shaped as {source, name, message}. Messages are
fixed generic strings, never raw exception text, to avoid leaking
URLs or credential fragments. get_ha_events and get_google_events now
return (events, errors) tuples so per-calendar failures propagate to
the caller in addition to account-level failures. Frontend toast now
picks its label from err.source instead of assuming Google/err.email.

backend/routers/caldav_router.py

@@ -300,6 +300,7 @@ def get_events(
         end_dt = end_dt.replace(tzinfo=timezone.utc)
 
     all_events = []
+    sync_errors = []
     accounts = (
         db.query(models.CalDAVAccount)
         .filter(
@@ -333,6 +334,11 @@ def get_events(
                 logger.error(
                     "Error fetching calendar %s: %s", calendar.id, exc
                 )
+                sync_errors.append({
+                    "source": "caldav",
+                    "name": f"{account.username} – {calendar.name}",
+                    "message": "Sync fehlgeschlagen",
+                })
 
     # ── Local calendar events (own + shared + group calendars) ─────────────
     readable_ids = permissions.readable_local_calendar_ids(db, current_user)
@@ -414,13 +420,18 @@ def get_events(
         .filter(models.GoogleAccount.user_id == current_user.id)
         .all()
     )
-    google_errors = []
     for g_acc in google_accounts:
         try:
-            all_events.extend(get_google_events(g_acc, start_dt, end_dt, db))
+            g_events, g_errors = get_google_events(g_acc, start_dt, end_dt, db)
+            all_events.extend(g_events)
+            sync_errors.extend(g_errors)
         except Exception as exc:
             logger.error("Error fetching Google Calendar for %s: %s", g_acc.email, exc)
-            google_errors.append({"email": g_acc.email})
+            sync_errors.append({
+                "source": "google",
+                "name": g_acc.email,
+                "message": "Sync fehlgeschlagen",
+            })
 
     # ── Home Assistant events ─────────────────────────────
     from routers.homeassistant_router import get_ha_events
@@ -431,11 +442,18 @@ def get_events(
     )
     for ha_acc in ha_accounts:
         try:
-            all_events.extend(get_ha_events(ha_acc, start_dt, end_dt, db))
+            ha_events, ha_errors = get_ha_events(ha_acc, start_dt, end_dt, db)
+            all_events.extend(ha_events)
+            sync_errors.extend(ha_errors)
         except Exception as exc:
             logger.error("Error fetching HA events for %s: %s", ha_acc.name, exc)
+            sync_errors.append({
+                "source": "homeassistant",
+                "name": ha_acc.name,
+                "message": "Sync fehlgeschlagen",
+            })
 
-    return {"events": all_events, "errors": google_errors}
+    return {"events": all_events, "errors": sync_errors}
 
 
 @router.post("/events")

backend/routers/google_router.py

@@ -382,8 +382,13 @@ def update_calendar(
 
 # ── Events ───────────────────────────────────────────────
 
-def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt: datetime, db: Session) -> list:
-    """Fetch events from all enabled Google calendars for an account."""
+def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt: datetime, db: Session) -> tuple:
+    """Fetch events from all enabled Google calendars for an account.
+
+    Returns (events, errors) — errors is a list of
+    {"source": "google", "name": ..., "message": ...} dicts for any
+    calendar that failed to sync. Never includes raw exception text.
+    """
     try:
         token = _refresh_access_token(account, db)
     except Exception as exc:
@@ -391,6 +396,7 @@ def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt:
         raise
 
     all_events = []
+    errors = []
     for gcal in account.calendars:
         if not gcal.enabled or gcal.sidebar_hidden:
             continue
@@ -409,8 +415,13 @@ def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt:
                 all_events.append(_parse_google_event(ev, gcal.id, gcal.name, gcal.color or "#4285f4"))
         except Exception as exc:
             logger.error("Error fetching events for calendar %s (%s): %s", gcal.name, gcal.cal_id, exc)
+            errors.append({
+                "source": "google",
+                "name": f"{account.email} – {gcal.name}",
+                "message": "Sync fehlgeschlagen",
+            })
 
-    return all_events
+    return all_events, errors
 
 
 class GoogleEventCreate(BaseModel):

backend/routers/homeassistant_router.py

@@ -313,8 +313,15 @@ def _parse_ha_event(ev: dict, cal_db_id: int, cal_name: str, cal_color: str) ->
     }
 
 
-def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_dt: datetime, db: Session) -> list:
+def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_dt: datetime, db: Session) -> tuple:
+    """Fetch events from all enabled HA calendars for an account.
+
+    Returns (events, errors) — errors is a list of
+    {"source": "homeassistant", "name": ..., "message": ...} dicts for any
+    calendar that failed to sync. Never includes raw exception text.
+    """
     all_events = []
+    errors = []
     try:
         token = _get_valid_token(account, db)
     except Exception as exc:
@@ -330,7 +337,12 @@ def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_
                 all_events.append(_parse_ha_event(ev, cal.id, cal.name, color))
         except Exception as exc:
             logger.error("HA event fetch error %s (%s): %s", cal.entity_id, account.name, exc)
-    return all_events
+            errors.append({
+                "source": "homeassistant",
+                "name": f"{account.name} – {cal.name}",
+                "message": "Sync fehlgeschlagen",
+            })
+    return all_events, errors
 
 
 # ── Serialization ─────────────────────────────────────────