fix: DST-aware calendar and ghost recurrence guard

backend/mvp.py

@@ -4,6 +4,7 @@ import re
 from datetime import UTC, date, datetime, time, timedelta
 from pathlib import Path
 from uuid import UUID
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
 from fastapi import APIRouter, Depends, File, HTTPException, Query, Response, UploadFile
 from fastapi.responses import FileResponse
@@ -120,6 +121,69 @@ def occurrences(rule: str, starts: datetime, start: datetime, end: datetime, cut
     return result
 
 
+def is_occurrence(rule: str, starts: datetime, at: datetime) -> bool:
+    """Return True when `at` is an occurrence this rule actually generates."""
+    parts = parse_rrule(rule)
+    interval = int(parts.get("INTERVAL", 1))
+    if starts.tzinfo is None:
+        starts = starts.replace(tzinfo=UTC)
+    if at.tzinfo is None:
+        at = at.replace(tzinfo=UTC)
+    if at < starts:
+        return False
+    if "UNTIL" in parts:
+        until = datetime.fromisoformat(parts["UNTIL"])
+        until = until.replace(tzinfo=UTC) if until.tzinfo is None else until
+        if at > until:
+            return False
+    if "COUNT" in parts:
+        count = int(parts["COUNT"])
+        match = 0
+        cursor = starts
+        guard = 0
+        while cursor <= at and guard < 40000:
+            if parts["FREQ"] == "DAILY":
+                include = (cursor.date() - starts.date()).days % interval == 0
+            elif parts["FREQ"] == "WEEKLY":
+                days = {_WEEKDAYS[x] for x in parts.get("BYDAY", list(_WEEKDAYS)[starts.weekday()]).split(",")}
+                include = cursor.weekday() in days and ((cursor.date() - starts.date()).days // 7) % interval == 0
+            elif parts["FREQ"] == "MONTHLY":
+                month_delta = (cursor.year - starts.year) * 12 + cursor.month - starts.month
+                month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
+                include = month_delta % interval == 0 and cursor.day in month_days
+            else:
+                years = cursor.year - starts.year
+                months = {int(x) for x in parts.get("BYMONTH", str(starts.month)).split(",")}
+                month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
+                include = years % interval == 0 and cursor.month in months and cursor.day in month_days
+            if include and cursor >= starts:
+                match += 1
+                if cursor == at:
+                    return True
+                if match >= count:
+                    return False
+            guard += 1
+            cursor += timedelta(days=1)
+        return False
+    if parts["FREQ"] == "DAILY":
+        return (at.date() - starts.date()).days % interval == 0
+    if parts["FREQ"] == "WEEKLY":
+        days = {_WEEKDAYS[x] for x in parts.get("BYDAY", list(_WEEKDAYS)[starts.weekday()]).split(",")}
+        return at.weekday() in days and ((at.date() - starts.date()).days // 7) % interval == 0
+    if parts["FREQ"] == "MONTHLY":
+        month_delta = (at.year - starts.year) * 12 + at.month - starts.month
+        month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
+        return month_delta % interval == 0 and at.day in month_days
+    years = at.year - starts.year
+    months = {int(x) for x in parts.get("BYMONTH", str(starts.month)).split(",")}
+    month_days = {int(x) for x in parts.get("BYMONTHDAY", str(starts.day)).split(",")}
+    return years % interval == 0 and at.month in months and at.day in month_days
+
+
+def is_occurrence_utc(rule: str, starts: datetime, at: datetime) -> bool:
+    return is_occurrence(rule, starts, at)
+
+
 async def owned_task(db, user_id, task_id):
     task = await db.scalar(select(Task).where(Task.id == task_id, Task.user_id == user_id, Task.deleted_at.is_(None)))
     if not task:
@@ -134,6 +198,12 @@ async def owned_recurrence(db, user_id, recurrence_id):
     return row
 
 
+def ensure_real_occurrence(template: RecurrenceTemplate, occurrence_at: datetime) -> None:
+    """Reject occurrence_at values that are not valid occurrences of this recurrence rule."""
+    if not is_occurrence(template.rrule, template.starts_at, occurrence_at):
+        raise HTTPException(422, "occurrence_at 不是该重复规则的有效发生时刻")
+
+
 @router.post("/recurrences", status_code=201)
 async def create_recurrence(payload: RecurrenceCreate, user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
     task = await owned_task(db, user.id, payload.task_id)
@@ -149,12 +219,15 @@ async def create_recurrence(payload: RecurrenceCreate, user: User = Depends(curr
 
 
 @router.get("/calendar")
-async def calendar(start: date, end: date, timezone_offset: int = Query(default=0, ge=-840, le=840), user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
+async def calendar(start: date, end: date, timezone: str = Query(default="UTC", pattern=r"^[A-Za-z_+-]+(/[A-Za-z_+-]+)*$"), user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
     if end < start or (end - start).days > 366:
         raise HTTPException(422, "日期范围无效或超过一年")
-    offset = timedelta(minutes=timezone_offset)
-    start_dt = datetime.combine(start, time.min, tzinfo=UTC) - offset
-    end_dt = datetime.combine(end + timedelta(days=1), time.min, tzinfo=UTC) - offset - timedelta(microseconds=1)
+    try:
+        zone = ZoneInfo(timezone)
+    except ZoneInfoNotFoundError:
+        raise HTTPException(422, "未知时区")
+    start_dt = datetime.combine(start, time.min, tzinfo=zone).astimezone(UTC)
+    end_dt = (datetime.combine(end + timedelta(days=1), time.min, tzinfo=zone)).astimezone(UTC) - timedelta(microseconds=1)
     recurrence_rows = (await db.execute(select(RecurrenceTemplate, Task).join(Task).where(RecurrenceTemplate.user_id == user.id, Task.deleted_at.is_(None)))).all()
     template_ids = [template.id for template, _ in recurrence_rows]
     exception_rows = [] if not template_ids else list((await db.scalars(select(RecurrenceException).where(RecurrenceException.template_id.in_(template_ids)))).all())
@@ -189,23 +262,24 @@ async def calendar(start: date, end: date, timezone_offset: int = Query(default=
     } for task in normal_tasks]
     for template, task in recurrence_rows:
         exceptions = exceptions_by_template.get(template.id, {})
-        generation_start = min(start_dt, *(exceptions.keys() or [start_dt]))
-        generated = occurrences(template.rrule, template.starts_at, generation_start, end_dt, template.ends_at)
-        occurrence_keys = {as_utc(at) for at in generated}
-        for at in generated:
-            exception = exceptions.get(at)
+        # Render events that this recurrence generates: real occurrences
+        # whose displayed (possibly moved) due_at falls inside the window.
+        for at in occurrences(template.rrule, template.starts_at, template.starts_at, end_dt, template.ends_at):
+            exception = exceptions.get(as_utc(at))
             if exception and exception.deleted:
                 continue
             due_at = as_utc(exception.due_at) if exception and exception.due_at else at
             if due_at < start_dt or due_at > end_dt:
                 continue
             output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": at, "title": exception.title if exception and exception.title else task.title, "due_at": due_at, "completed": bool(exception and exception.completed)})
+        # Occurrences moved far enough that their original slot falls before
+        # the start of generation: show them at their moved due_at. Ghost
+        # occurrence_at values are already rejected at write time.
         for occurrence_at, exception in exceptions.items():
-            if occurrence_at in occurrence_keys or exception.deleted or exception.due_at is None:
+            if exception.deleted or exception.due_at is None:
                 continue
-            due_at = as_utc(exception.due_at)
-            if start_dt <= due_at <= end_dt:
-                output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": occurrence_at, "title": exception.title or task.title, "due_at": due_at, "completed": exception.completed})
+            if as_utc(occurrence_at) >= as_utc(template.starts_at) and start_dt <= as_utc(exception.due_at) <= end_dt:
+                output.append({"recurrence_id": template.id, "task_id": task.id, "occurrence_at": occurrence_at, "title": exception.title or task.title, "due_at": as_utc(exception.due_at), "completed": bool(exception.completed)})
     return sorted(output, key=lambda item: item["occurrence_at"].replace(tzinfo=UTC) if item["occurrence_at"].tzinfo is None else item["occurrence_at"])
 
 
@@ -224,11 +298,13 @@ async def edit_recurrence(recurrence_id: UUID, payload: RecurrenceChange, scope:
     task = await owned_task(db, user.id, template.task_id)
     if scope == "this":
         if not occurrence_at: raise HTTPException(422, "需要 occurrence_at")
+        ensure_real_occurrence(template, occurrence_at)
         row = await upsert_exception(db, template.id, occurrence_at)
         if payload.title is not None: row.title = payload.title
         if payload.due_at is not None: row.due_at = payload.due_at
     elif scope == "this-and-future":
         if not occurrence_at: raise HTTPException(422, "需要 occurrence_at")
+        ensure_real_occurrence(template, occurrence_at)
         template.ends_at = occurrence_at - timedelta(microseconds=1)
         if payload.rrule:
             parse_rrule(payload.rrule)
@@ -246,6 +322,7 @@ async def edit_recurrence(recurrence_id: UUID, payload: RecurrenceChange, scope:
 @router.post("/recurrences/{recurrence_id}/complete")
 async def complete_occurrence(recurrence_id: UUID, payload: OccurrenceComplete, user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
     template = await owned_recurrence(db, user.id, recurrence_id)
+    ensure_real_occurrence(template, payload.occurrence_at)
     row = await upsert_exception(db, template.id, payload.occurrence_at); row.completed = True
     audit(db, user.id, "complete", "task", template.task_id, occurrence_at=payload.occurrence_at.isoformat())
     await db.commit(); return {"completed": True}
@@ -256,9 +333,11 @@ async def delete_recurrence(recurrence_id: UUID, scope: str = Query("all", patte
     template = await owned_recurrence(db, user.id, recurrence_id)
     if scope == "this":
         if not occurrence_at: raise HTTPException(422, "需要 occurrence_at")
+        ensure_real_occurrence(template, occurrence_at)
         row = await upsert_exception(db, template.id, occurrence_at); row.deleted = True
     elif scope == "this-and-future":
         if not occurrence_at: raise HTTPException(422, "需要 occurrence_at")
+        ensure_real_occurrence(template, occurrence_at)
         template.ends_at = occurrence_at - timedelta(microseconds=1)
     else: await db.delete(template)
     await db.commit(); return Response(status_code=204)

frontend/src/MvpPanel.vue

@@ -65,8 +65,8 @@ async function loadCalendar(range?: { startStr?: string; endStr?: string }) {
   endExclusive.setDate(endExclusive.getDate() - 1)
   const end = dateKey(endExclusive)
   await safe(async()=>{
-    const tzOffset = -new Date().getTimezoneOffset()
-    const rows = await request(`/calendar?start=${start}&end=${end}&timezone_offset=${tzOffset}`) as Array<{id?:string;task_id:string;recurrence_id?:string|null;title:string;due_at?:string;occurrence_at:string;version?:number}>
+    const tzName = Intl.DateTimeFormat().resolvedOptions().timeZone || 'UTC'
+    const rows = await request(`/calendar?start=${start}&end=${end}&timezone=${encodeURIComponent(tzName)}`) as Array<{id?:string;task_id:string;recurrence_id?:string|null;title:string;due_at?:string;occurrence_at:string;version?:number}>
     calendarTasks.value = rows.map(row=>({
       id: row.recurrence_id ? `${row.task_id}:${row.occurrence_at}` : (row.id ?? row.task_id),
       title: row.title,

tests/test_mvp_backend.py

@@ -114,7 +114,7 @@ def test_calendar_respects_timezone_boundaries_and_moved_occurrences(client):
 
     calendar = client.get(
         "/api/v1/calendar",
-        params={"start": "2026-09-01", "end": "2026-09-30", "timezone_offset": 480},
+        params={"start": "2026-09-01", "end": "2026-09-30", "timezone": "Asia/Shanghai"},
     ).json()
 
     assert any(row.get("id") == inside["id"] for row in calendar)
@@ -122,6 +122,38 @@ def test_calendar_respects_timezone_boundaries_and_moved_occurrences(client):
     assert any(row.get("recurrence_id") == recurrence["id"] and row["due_at"].startswith("2026-09-20") for row in calendar)
 
 
+def test_calendar_rejects_unknown_timezone(client):
+    boot(client)
+    response = client.get("/api/v1/calendar", params={"start": "2026-09-01", "end": "2026-09-30", "timezone": "Mars/Olympus"})
+    assert response.status_code == 422
+
+
+def test_recurrence_mutations_reject_ghost_occurrences(client):
+    inbox = boot(client)
+    task = client.post(
+        "/api/v1/tasks",
+        json={"title": "每周任务", "list_id": inbox["id"], "due_at": "2026-09-07T09:00:00Z"},
+    ).json()
+    recurrence = client.post(
+        "/api/v1/recurrences", json={"task_id": task["id"], "rrule": "FREQ=WEEKLY;COUNT=3"}
+    ).json()
+    # 9/7 and 9/14 are real occurrences; 9/9 is NOT part of this series.
+    ghost_patch = client.patch(
+        f"/api/v1/recurrences/{recurrence['id']}",
+        params={"scope": "this", "occurrence_at": "2026-09-09T09:00:00Z"},
+        json={"due_at": "2026-09-20T09:00:00Z"},
+    )
+    assert ghost_patch.status_code == 422
+
+    calendar = client.get(
+        "/api/v1/calendar",
+        params={"start": "2026-09-01", "end": "2026-09-30", "timezone": "UTC"},
+    ).json()
+
+    assert not any(row.get("recurrence_id") == recurrence["id"] and row["due_at"].startswith("2026-09-20") for row in calendar)
+    assert len([row for row in calendar if row.get("recurrence_id") == recurrence["id"]]) == 3
+
+
 def test_habit_logs_support_date_range_filter(client):
     boot(client)
     habit = client.post("/api/v1/habits", json={"name": "跑步", "kind": "boolean", "schedule_type": "daily"}).json()