Fix cross-provider season deduplication

Resolve missing Season TVDB IDs from cached parent TV rows and add Calendar regressions.

Fixes #938

Author: dannyvfilms

src/app/services/item_merge.py

@@ -252,10 +252,10 @@ def dedupe_cross_provider_items(items: list[Item], preferred_source: str) -> lis
     reconciles them (#620), and a user may legitimately track a show under
     both identities on purpose - in which case both trees stay, and only the
     non-preferred one should be hidden from render-time listings (#639).
-    This hides the item the user doesn't prefer using only the already-cached
-    `provider_external_ids["tvdb_id"]` mapping - never a title match, and
-    never a network call, so it can't misfire on unrelated shows and can't
-    slow down rendering.
+    This hides the item the user doesn't prefer using only verified, cached
+    `provider_external_ids["tvdb_id"]` mappings - never a title match, and
+    never a network call. Season rows that lack their own mapping inherit the
+    cached mapping from the matching TMDB TV row through one bulk lookup.
     """
     tvdb_by_key = {
         (
@@ -271,6 +271,28 @@ def dedupe_cross_provider_items(items: list[Item], preferred_source: str) -> lis
     if not tvdb_by_key:
         return items
 
+    season_parent_tvdb_ids = {}
+    tmdb_season_media_ids = {
+        item.media_id
+        for item in items
+        if item.source == Sources.TMDB.value
+        and item.media_type == MediaTypes.SEASON.value
+        and not (item.provider_external_ids or {}).get("tvdb_id")
+    }
+    if tmdb_season_media_ids:
+        for parent in (
+            Item.objects.filter(
+                media_id__in=tmdb_season_media_ids,
+                source=Sources.TMDB.value,
+                media_type=MediaTypes.TV.value,
+            )
+            .order_by("media_id", "id")
+            .values("media_id", "provider_external_ids")
+        ):
+            tvdb_id = (parent["provider_external_ids"] or {}).get("tvdb_id")
+            if tvdb_id and parent["media_id"] not in season_parent_tvdb_ids:
+                season_parent_tvdb_ids[parent["media_id"]] = str(tvdb_id)
+
     hidden_ids = set()
     for item in items:
         if item.source != Sources.TMDB.value or item.media_type not in (
@@ -279,6 +301,8 @@ def dedupe_cross_provider_items(items: list[Item], preferred_source: str) -> lis
         ):
             continue
         tvdb_id = (item.provider_external_ids or {}).get("tvdb_id")
+        if not tvdb_id and item.media_type == MediaTypes.SEASON.value:
+            tvdb_id = season_parent_tvdb_ids.get(item.media_id)
         if not tvdb_id:
             continue
         counterpart = tvdb_by_key.get(

src/app/tests/test_item_merge.py

@@ -240,6 +240,92 @@ def test_playback_progress_collision_keeps_keepers_row(self):
         self.assertEqual(keeper_progress.position_seconds, 900)
 
 
+class DedupeCrossProviderItemsTests(TestCase):
+    """Render-time dedupe uses verified provider identity without network calls."""
+
+    def _season_pair(self, *, parent_tvdb_id="81189"):
+        tmdb_show = Item.objects.create(
+            media_id="1396",
+            source=Sources.TMDB.value,
+            media_type=MediaTypes.TV.value,
+            title="Breaking Bad",
+            image="",
+            provider_external_ids={"tvdb_id": parent_tvdb_id},
+        )
+        tvdb_show = Item.objects.create(
+            media_id=parent_tvdb_id,
+            source=Sources.TVDB.value,
+            media_type=MediaTypes.TV.value,
+            title="Breaking Bad",
+            image="",
+        )
+        tmdb_season = Item.objects.create(
+            media_id=tmdb_show.media_id,
+            source=Sources.TMDB.value,
+            media_type=MediaTypes.SEASON.value,
+            season_number=1,
+            title="Breaking Bad",
+            image="",
+        )
+        tvdb_season = Item.objects.create(
+            media_id=tvdb_show.media_id,
+            source=Sources.TVDB.value,
+            media_type=MediaTypes.SEASON.value,
+            season_number=1,
+            title="Breaking Bad",
+            image="",
+        )
+        return tmdb_season, tvdb_season
+
+    def test_season_falls_back_to_parent_tvdb_id_and_honors_preference(self):
+        tmdb_season, tvdb_season = self._season_pair()
+
+        with self.assertNumQueries(1):
+            tmdb_result = item_merge.dedupe_cross_provider_items(
+                [tmdb_season, tvdb_season],
+                Sources.TMDB.value,
+            )
+        tvdb_result = item_merge.dedupe_cross_provider_items(
+            [tmdb_season, tvdb_season],
+            Sources.TVDB.value,
+        )
+
+        self.assertEqual(tmdb_result, [tmdb_season])
+        self.assertEqual(tvdb_result, [tvdb_season])
+
+    @patch("app.services.item_merge.tmdb.resolve_tvdb_id_for_tmdb_show")
+    def test_missing_parent_id_does_not_match_same_title(self, mock_resolve):
+        tmdb_season, tvdb_season = self._season_pair(parent_tvdb_id="81189")
+        Item.objects.filter(pk=tmdb_season.pk).update(provider_external_ids={})
+        Item.objects.filter(media_id="1396", source=Sources.TMDB.value).update(
+            provider_external_ids={},
+        )
+
+        result = item_merge.dedupe_cross_provider_items(
+            [tmdb_season, tvdb_season],
+            Sources.TMDB.value,
+        )
+
+        self.assertCountEqual(result, [tmdb_season, tvdb_season])
+        mock_resolve.assert_not_called()
+
+    def test_explicit_season_id_takes_precedence_over_parent(self):
+        tmdb_season, tvdb_season = self._season_pair()
+        Item.objects.filter(
+            media_id="1396",
+            source=Sources.TMDB.value,
+            media_type=MediaTypes.TV.value,
+        ).update(provider_external_ids={"tvdb_id": "99999"})
+        tmdb_season.provider_external_ids = {"tvdb_id": tvdb_season.media_id}
+
+        result = item_merge.dedupe_cross_provider_items(
+            [tmdb_season, tvdb_season],
+            Sources.TVDB.value,
+        )
+
+        self.assertEqual(result, [tvdb_season])
+
+
 class FindCrossProviderDuplicateTests(TestCase):
     """Verified-identity lookup only - never title matching."""
 

src/events/models.py

@@ -105,8 +105,9 @@ def _cross_provider_hidden_season_item_ids(self, user, enabled_types):
         TVDB identity (the #620 dual-identity model); each identity gets its
         own independent Season `Item`s and `Event`s. Without this, the
         calendar shows the same real episode twice - once per identity
-        (#639). Uses the same verified `provider_external_ids["tvdb_id"]`
-        based dedup already used for Home rows.
+        (#639). Uses the same verified cached cross-provider mapping already
+        used for Home rows; Season rows fall back to their matching TMDB TV
+        item's mapping when the child row has no `tvdb_id` of its own.
         """
         if not (
             MediaTypes.TV.value in enabled_types

src/events/tests/test_models.py

@@ -345,7 +345,6 @@ def _tv_pair(self, tvdb_id="81189"):
             source=Sources.TMDB.value,
             image="",
             season_number=1,
-            provider_external_ids={"tvdb_id": tvdb_id},
         )
         tvdb_season = Item.objects.create(
             title="Breaking Bad",