fix(classification): restore legacy alias fields after rule deletion

app/application/classification/migration.py

@@ -209,7 +209,7 @@ def migrate_legacy_category_config(
 def legacy_extension_fields_from_policy(
     policy: ClassificationPolicy,
 ) -> tuple[ClassificationFieldDefinition, ...]:
-    """按策略条件顺序重建可直接注册的 TMDB 旧比较扩展字段声明。"""
+    """按策略条件和别名重建可直接注册的 TMDB 旧比较扩展字段声明。"""
     context = _MigrationContext()
     for rule in policy.rules:
         for field_id in _condition_field_ids(rule.when):
@@ -220,6 +220,15 @@ def legacy_extension_fields_from_policy(
                 continue
             for media_type in rule.media_types:
                 context.register_extension_field(field_name, media_type)
+    # 别名与规则分开保存；删除最后一条规则后仍需恢复字段，避免重启后校验失败。
+    for field_id in policy.field_aliases:
+        if field_id in context.field_media_types or not field_id.startswith(_EXTENSION_PREFIX):
+            continue
+        field_name = field_id.removeprefix(_EXTENSION_PREFIX)
+        if not _SAFE_FIELD_SEGMENT.fullmatch(field_name):
+            continue
+        for media_type in _MEDIA_TYPES.values():
+            context.register_extension_field(field_name, media_type)
     return context.build_field_definitions()
 
 

tests/test_media_classification_legacy.py

@@ -208,6 +208,24 @@ def test_default_style_config_preserves_order_and_uses_safe_standard_fields() ->
     assert origin_country.replacement_field == "media.countries"
 
 
+def test_deleted_legacy_rules_keep_alias_only_fields_registered() -> None:
+    """删除最后一条旧规则后，仍需登记孤立别名字段以通过策略校验。"""
+    migrated = migrate_legacy_category_config(
+        {
+            "movie": {"中文电影": {"original_language": "zh"}},
+            "tv": {},
+        }
+    )
+    policy = migrated.policy.model_copy(deep=True, update={"rules": []})
+
+    fields = legacy_extension_fields_from_policy(policy)
+
+    assert [field.id for field in fields] == [
+        "extensions.themoviedb.original_language"
+    ]
+    assert ClassificationPolicyValidator.validate(policy, fields).valid
+
+
 def test_first_empty_rule_becomes_global_fallback_and_later_entries_are_disabled() -> None:
     """首个全空项应成为媒体类型全局兜底，后续分类和规则保留但永远禁用。"""
     result = migrate_legacy_category_config(

tests/test_media_classification_startup.py

@@ -10,11 +10,14 @@ from typing import Any, TypeVar, cast
 import pytest
 
 from app.api.endpoints import media as media_endpoint
+from app.application.classification.analysis import ClassificationAnalysisService
 from app.application.classification.configuration import (
     ClassificationPolicyConfigurationService,
     build_default_classification_policy,
+    with_default_music_classification,
 )
 from app.application.classification.contract import ClassificationPolicyConflictError
+from app.application.classification.legacy import migrate_legacy_category_config
 from app.application.classification.runtime import ClassificationRuntime
 from app.schemas.category import (
     ClassificationConditionGroup,
@@ -142,6 +145,56 @@ async def test_existing_policy_never_reads_legacy_yaml(
     assert store.write_count == 0
 
 
+@pytest.mark.asyncio  # type: ignore[misc]
+async def test_deleted_legacy_rules_keep_validation_and_impact_analysis_working(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    """重启加载只剩旧别名的策略后，校验和影响分析仍应可用。"""
+    migrated = migrate_legacy_category_config(
+        {
+            "movie": {"中文电影": {"original_language": "zh"}},
+            "tv": {},
+        }
+    )
+    policy = with_default_music_classification(migrated.policy).model_copy(
+        deep=True,
+        update={"rules": []},
+    )
+    state = ClassificationPolicyState(active=policy)
+    store = _MemoryPolicyStore(state)
+    system_config = _SystemConfig(
+        {
+            SystemConfigKey.MediaClassificationPolicy.value: state.model_dump(
+                mode="json"
+            )
+        }
+    )
+    monkeypatch.setattr(
+        classification_composition,
+        "SystemConfigClassificationPolicyStore",
+        lambda *_args: store,
+    )
+
+    composition = await classification_composition.compose_classification(
+        executor=cast(Any, _InlineExecutor()),
+        settings=cast(Any, SimpleNamespace(CONFIG_PATH=tmp_path)),
+        system_config=cast(Any, system_config),
+    )
+    analysis = ClassificationAnalysisService(composition.runtime.service)
+
+    assert analysis.validate(policy).valid
+    impact = await analysis.impact(
+        policy,
+        expected_revision=1,
+        sample_limit=10,
+        example_limit=2,
+    )
+    assert impact.baseline_revision == 1
+    assert impact.candidate_revision == 2
+    assert impact.sample_count == 0
+
+
 @pytest.mark.asyncio  # type: ignore[misc]
 async def test_untouched_legacy_default_policy_gains_music_rules_once(
     monkeypatch: pytest.MonkeyPatch,