From 1a707ff179981da7974f35bd0c58663a5c74e9bd Mon Sep 17 00:00:00 2001
From: Kyle Pope <kyle.a.pope@outlook.com>
Date: Sun, 22 Feb 2026 01:50:52 +0800
Subject: [PATCH] Fix weekly recurrence crash: null fields in serialized rule

model_dump() includes None values for optional RecurrenceRule fields.
When serialized to JSON, these become explicit nulls (e.g. "weekday": null).
The recurrence service then does int(None) which raises TypeError.

Fix: strip None values when serializing rule to JSON, and add defensive
None handling in recurrence service for all rule.get() calls.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 backend/app/routers/events.py      |  5 +++--
 backend/app/services/recurrence.py | 10 +++++-----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/backend/app/routers/events.py b/backend/app/routers/events.py
index 6b2b022..a3a655c 100644
--- a/backend/app/routers/events.py
+++ b/backend/app/routers/events.py
@@ -192,8 +192,9 @@ async def create_event(
         data["calendar_id"] = await _get_default_calendar_id(db)
 
     # Serialize RecurrenceRule object to JSON string for DB storage
+    # Exclude None values so defaults in recurrence service work correctly
     rule_obj = data.pop("recurrence_rule", None)
-    rule_json: Optional[str] = json.dumps(rule_obj) if rule_obj else None
+    rule_json: Optional[str] = json.dumps({k: v for k, v in rule_obj.items() if v is not None}) if rule_obj else None
 
     if rule_json:
         # Parent template: is_recurring=True, no parent_event_id
@@ -282,7 +283,7 @@ async def update_event(
     # Serialize RecurrenceRule → JSON string if present in update payload
     rule_obj = update_data.pop("recurrence_rule", None)
     if rule_obj is not None:
-        update_data["recurrence_rule"] = json.dumps(rule_obj) if rule_obj else None
+        update_data["recurrence_rule"] = json.dumps({k: v for k, v in rule_obj.items() if v is not None}) if rule_obj else None
 
     start = update_data.get("start_datetime", event.start_datetime)
     end_dt = update_data.get("end_datetime", event.end_datetime)
diff --git a/backend/app/services/recurrence.py b/backend/app/services/recurrence.py
index 4fcddb1..cb0406d 100644
--- a/backend/app/services/recurrence.py
+++ b/backend/app/services/recurrence.py
@@ -85,7 +85,7 @@ def generate_occurrences(
         )
 
     if rule_type == "every_n_days":
-        interval: int = int(rule.get("interval", 1))
+        interval: int = int(rule.get("interval") or 1)
         if interval < 1:
             interval = 1
         current = parent_start + timedelta(days=interval)
@@ -94,7 +94,7 @@ def generate_occurrences(
             current += timedelta(days=interval)
 
     elif rule_type == "weekly":
-        weekday: int = int(rule.get("weekday", parent_start.weekday()))
+        weekday: int = int(rule.get("weekday") if rule.get("weekday") is not None else parent_start.weekday())
         # Start from the week after the parent
         days_ahead = (weekday - parent_start.weekday()) % 7
         if days_ahead == 0:
@@ -105,8 +105,8 @@ def generate_occurrences(
             current += timedelta(weeks=1)
 
     elif rule_type == "monthly_nth_weekday":
-        week: int = int(rule.get("week", 1))
-        weekday = int(rule.get("weekday", parent_start.weekday()))
+        week: int = int(rule.get("week") or 1)
+        weekday = int(rule.get("weekday") if rule.get("weekday") is not None else parent_start.weekday())
         # Advance month by month
         year, month = parent_start.year, parent_start.month
         # Move to the next month from the parent
@@ -139,7 +139,7 @@ def generate_occurrences(
                 break
 
     elif rule_type == "monthly_date":
-        day: int = int(rule.get("day", parent_start.day))
+        day: int = int(rule.get("day") or parent_start.day)
         year, month = parent_start.year, parent_start.month
         month += 1
         if month > 12: