feat(tags): merge repoints image_tag and tag_suggestion_rejection with dedup

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_tag_merge.py

@@ -1,4 +1,5 @@
 import pytest
+from sqlalchemy import select
 
 from backend.app.models import Tag, TagKind, image_tag
 from backend.app.models.tag_allowlist import TagAllowlist
@@ -129,3 +130,79 @@ async def test_merge_empty_tags_returns_result(db):
     assert result.alias_created is False
     assert result.source_deleted is True
     assert await db.get(Tag, a.id) is None
+
+
+@pytest.mark.asyncio
+async def test_merge_moves_image_tags_and_counts(db):
+    svc = TagService(db)
+    a = await svc.find_or_create("SrcIT", TagKind.general)
+    b = await svc.find_or_create("TgtIT", TagKind.general)
+    i1, i2 = await _img(db), await _img(db)
+    await svc.add_to_image(i1, a.id, source="manual")
+    await svc.add_to_image(i2, a.id, source="manual")
+    result = await svc.merge(a.id, b.id)
+    assert result.merged_count == 2
+    rows = (
+        await db.execute(
+            image_tag.select().where(image_tag.c.tag_id == b.id)
+        )
+    ).all()
+    assert {r.image_record_id for r in rows} == {i1, i2}
+    assert (
+        await db.execute(
+            image_tag.select().where(image_tag.c.tag_id == a.id)
+        )
+    ).first() is None
+
+
+@pytest.mark.asyncio
+async def test_merge_dedups_image_tag_when_image_has_both(db):
+    svc = TagService(db)
+    a = await svc.find_or_create("SrcDup", TagKind.general)
+    b = await svc.find_or_create("TgtDup", TagKind.general)
+    img = await _img(db)
+    await svc.add_to_image(img, a.id, source="manual")
+    await svc.add_to_image(img, b.id, source="manual")
+    result = await svc.merge(a.id, b.id)
+    # The image already had the target → that source row is dropped, not moved.
+    assert result.merged_count == 0
+    rows = (
+        await db.execute(
+            image_tag.select().where(
+                image_tag.c.image_record_id == img
+            )
+        )
+    ).all()
+    assert [r.tag_id for r in rows] == [b.id]
+
+
+@pytest.mark.asyncio
+async def test_merge_dedups_suggestion_rejections(db):
+    from backend.app.models.tag_suggestion_rejection import (
+        TagSuggestionRejection,
+    )
+
+    svc = TagService(db)
+    a = await svc.find_or_create("SrcRej", TagKind.general)
+    b = await svc.find_or_create("TgtRej", TagKind.general)
+    i1, i2 = await _img(db), await _img(db)
+    db.add(TagSuggestionRejection(image_record_id=i1, tag_id=a.id))
+    db.add(TagSuggestionRejection(image_record_id=i2, tag_id=a.id))
+    db.add(TagSuggestionRejection(image_record_id=i1, tag_id=b.id))
+    await db.flush()
+    await svc.merge(a.id, b.id)
+    rej = (
+        await db.execute(
+            select(TagSuggestionRejection).where(
+                TagSuggestionRejection.tag_id == b.id
+            )
+        )
+    ).scalars().all()
+    assert {r.image_record_id for r in rej} == {i1, i2}
+    assert (
+        await db.execute(
+            select(TagSuggestionRejection).where(
+                TagSuggestionRejection.tag_id == a.id
+            )
+        )
+    ).first() is None