fix(bangumi): inherit year for same-title entries across subtitle groups

When a new bangumi entry is created for an already-known show (same
official_title, different group/quality so no semantic merge), it now
inherits the existing entry's year. The save path is built as
`title (year)/Season N`, so a Mikan-parsed entry (which never fills
year) previously diverged into a separate library folder from a
TMDB-parsed sibling that had one. `_inherit_year` in add()/add_all()
copies the year from any non-deleted same-title row when the incoming
entry has none; a parsed year is never overwritten.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FAxVyRwrY7z5NotTtgnwVs

backend/src/module/database/bangumi.py

@@ -126,6 +126,21 @@ def _find_semantic_match(data: Bangumi, candidates: list[Bangumi]) -> Optional[B
     return None
 
 
+def _inherit_year(data: Bangumi, candidates: list[Bangumi]) -> None:
+    """新条目缺年份时继承同名已有条目的年份。
+
+    save path 由 ``official_title (year)`` 组成（downloader/path.py），同一部
+    番剧的不同订阅条目（不同字幕组/清晰度）若年份不一致，会被拆进两个媒体库
+    目录。Mikan 解析路径不填 year，因此从已有同名条目补齐。
+    """
+    if data.year:
+        return
+    for candidate in candidates:
+        if candidate.year:
+            data.year = candidate.year
+            return
+
+
 def match_bangumi_in_list(
     torrent_name: str, bangumi_list: list[Bangumi]
 ) -> Optional[Bangumi]:
@@ -152,6 +167,17 @@ class BangumiDatabase:
     def __init__(self, session: AsyncSession):
         self.session = session
 
+    async def _same_title_candidates(self, official_title: str) -> list[Bangumi]:
+        """加载与给定 official_title 同名的所有未删除条目。"""
+        statement = select(Bangumi).where(
+            and_(
+                Bangumi.official_title == official_title,
+                Bangumi.deleted == false(),
+            )
+        )
+        result = await self.session.execute(statement)
+        return list(result.scalars().all())
+
     async def find_semantic_duplicate(self, data: Bangumi) -> Optional[Bangumi]:
         """
         Find existing bangumi that semantically matches the new one.
@@ -166,15 +192,7 @@ class BangumiDatabase:
 
         Returns the matching Bangumi if found, None otherwise.
         """
-        statement = select(Bangumi).where(
-            and_(
-                Bangumi.official_title == data.official_title,
-                Bangumi.deleted == false(),
-            )
-        )
-        result = await self.session.execute(statement)
-        candidates = list(result.scalars().all())
-
+        candidates = await self._same_title_candidates(data.official_title)
         match = _find_semantic_match(data, candidates)
         if match:
             logger.debug(
@@ -249,7 +267,8 @@ class BangumiDatabase:
             return False
 
         # Check for semantic duplicate (same anime, different naming pattern)
-        semantic_match = await self.find_semantic_duplicate(data)
+        candidates = await self._same_title_candidates(data.official_title)
+        semantic_match = _find_semantic_match(data, candidates)
         if semantic_match:
             # Add as alias instead of creating new entry
             await self.add_title_alias(semantic_match.id, data.title_raw)
@@ -259,6 +278,7 @@ class BangumiDatabase:
             )
             return False  # Return False since we didn't add a new entry
 
+        _inherit_year(data, candidates)
         self.session.add(data)
         await self.session.commit()
         logger.debug("Insert %s into database.", data.official_title)
@@ -328,6 +348,7 @@ class BangumiDatabase:
                     f"'{semantic_match.title_raw}' (official: {d.official_title})"
                 )
             else:
+                _inherit_year(d, candidates_by_title.get(d.official_title, []))
                 really_to_add.append(d)
 
         # Also deduplicate within the batch itself

backend/src/test/test_database.py

@@ -455,6 +455,106 @@ async def test_add_with_semantic_duplicate_creates_alias(db_session):
     assert "Frieren Beyond Journey's End" in aliases
 
 
+async def test_add_same_title_new_entry_inherits_year(db_session):
+    """A new entry for an already-known anime (same official_title, different
+    group/quality so no semantic merge) must inherit the existing year, so both
+    entries build the same save path (title (year)/Season N)."""
+    db = BangumiDatabase(db_session)
+
+    existing = Bangumi(
+        official_title="躲在超市后门抽烟的两人",
+        year="2026",
+        title_raw="躲在超市后门抽烟的两人",
+        group_name="樱都字幕组",
+        dpi="1080p",
+        source="Baha",
+        subtitle="CHS",
+        rss_link="test1",
+    )
+    await db.add(existing)
+
+    new_entry = Bangumi(
+        official_title="躲在超市后门抽烟的两人",
+        year=None,
+        title_raw="Super no Ura de Yani Suu Futari",
+        group_name="Dynamis One",
+        dpi="1080p",
+        source="ABEMA",
+        subtitle="JPSC",
+        rss_link="test2",
+    )
+    result = await db.add(new_entry)
+
+    assert result is True  # different group/source: a new entry, not a merge
+    assert new_entry.year == "2026"
+
+
+async def test_add_same_title_keeps_own_year(db_session):
+    """An explicitly parsed year must not be overwritten by an existing entry's."""
+    db = BangumiDatabase(db_session)
+
+    await db.add(
+        Bangumi(
+            official_title="Frieren",
+            year="2023",
+            title_raw="Sousou no Frieren",
+            group_name="LoliHouse",
+            dpi="1080p",
+            source="Web",
+            subtitle="CHT",
+            rss_link="test1",
+        )
+    )
+
+    new_entry = Bangumi(
+        official_title="Frieren",
+        year="2024",
+        title_raw="Frieren S2",
+        group_name="OtherGroup",
+        dpi="720p",
+        source="Baha",
+        subtitle="CHS",
+        rss_link="test2",
+    )
+    result = await db.add(new_entry)
+
+    assert result is True
+    assert new_entry.year == "2024"
+
+
+async def test_add_all_same_title_new_entries_inherit_year(db_session):
+    """add_all() applies the same year inheritance as add()."""
+    db = BangumiDatabase(db_session)
+
+    await db.add(
+        Bangumi(
+            official_title="躲在超市后门抽烟的两人",
+            year="2026",
+            title_raw="躲在超市后门抽烟的两人",
+            group_name="樱都字幕组",
+            dpi="1080p",
+            source="Baha",
+            subtitle="CHS",
+            rss_link="test1",
+        )
+    )
+
+    new_entry = Bangumi(
+        official_title="躲在超市后门抽烟的两人",
+        year=None,
+        title_raw="Super no Ura de Yani Suu Futari",
+        group_name="Dynamis One",
+        dpi="1080p",
+        source="ABEMA",
+        subtitle="JPSC",
+        rss_link="test2",
+    )
+    added = await db.add_all([new_entry])
+
+    assert added == 1
+    assert new_entry.year == "2026"
+
+
 async def test_add_all_semantic_duplicates_across_batch_all_merged_as_aliases(
     db_session,
 ):