fix: validate segment durations with _safe_segment_duration + upgrade fallback logs to warning

- Add _safe_segment_duration() to handle None/invalid/negative/NaN values
- Swap dur_min/dur_max if dirty data has min > max
- Change fallback exception logs from DEBUG to WARNING for observability
- Add 7 unit tests for _safe_segment_duration
- 47 tests passing

apps/api/app/api/routes/templates_editor/clips.py

@@ -360,6 +360,22 @@ def batch_delete_editor_clips(
 
 
 
+def _safe_segment_duration(value, default: float) -> float:
+    """安全地将数据库中的时长值转换为正浮点数.
+
+    处理 None、无效类型、负数、NaN 等异常情况。
+    """
+    if value is None:
+        return default
+    try:
+        result = float(value)
+    except (ValueError, TypeError):
+        return default
+    if result != result or result <= 0:  # NaN check or non-positive
+        return default
+    return result
+
+
 def _get_template_segments(
     template_id: str,
     tpl_svc: EditTemplateService,
@@ -377,38 +393,35 @@ def _get_template_segments(
     try:
         clip_configs = tpl_svc.list_clip_configs(template_id)
         if clip_configs:
-            return sorted(
-                [
-                    (
-                        cc.order,
-                        float(cc.min_duration or _DEFAULT_EDITOR_CLIP_DURATION),
-                        float(
-                            cc.max_duration
-                            or cc.min_duration
-                            or _DEFAULT_EDITOR_CLIP_DURATION
-                        ),
-                    )
-                    for cc in clip_configs
-                ],
-                key=lambda x: x[0],
-            )
+            result = []
+            for cc in clip_configs:
+                dur_min = _safe_segment_duration(
+                    cc.min_duration, _DEFAULT_EDITOR_CLIP_DURATION
+                )
+                dur_max = _safe_segment_duration(
+                    cc.max_duration or cc.min_duration,
+                    _DEFAULT_EDITOR_CLIP_DURATION,
+                )
+                dur_min, dur_max = min(dur_min, dur_max), max(dur_min, dur_max)
+                result.append((cc.order, dur_min, dur_max))
+            return sorted(result, key=lambda x: x[0])
     except Exception:
-        logger.debug("新模板系统查询clip_configs失败，回退到旧系统", exc_info=True)
+        logger.warning("新模板系统查询clip_configs失败，回退到旧系统", exc_info=True)
 
     # 回退到旧模板系统（template_segments表）
     try:
         old_repo = SQLAlchemyTemplateRepository(db)
         segments = old_repo.list_segments(template_id)
         if segments:
-            return sorted(
-                [
-                    (s.segment_order, float(s.duration_min), float(s.duration_max))
-                    for s in segments
-                ],
-                key=lambda x: x[0],
-            )
+            result = []
+            for s in segments:
+                dur_min = _safe_segment_duration(s.duration_min, 0.0)
+                dur_max = _safe_segment_duration(s.duration_max, 0.0)
+                dur_min, dur_max = min(dur_min, dur_max), max(dur_min, dur_max)
+                result.append((s.segment_order, dur_min, dur_max))
+            return sorted(result, key=lambda x: x[0])
     except Exception:
-        logger.debug("旧模板系统查询segments失败", exc_info=True)
+        logger.warning("旧模板系统查询segments失败", exc_info=True)
 
     return []
 

tests/unit/test_mediakit_smart_clips.py

@@ -618,3 +618,45 @@ class TestFromAssetsByTemplateSegments:
         assert clips_data[0]["start_time"] == 15.0
         # 第二个片段（同一素材）不应使用推荐时间
         assert clips_data[1]["start_time"] != 15.0
+
+# ── _safe_segment_duration 单元测试 ─────────────────────────────────────────
+
+
+class TestSafeSegmentDuration:
+    """测试片段时长安全转换。"""
+
+    def test_normal_float(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration(3.5, 1.0) == 3.5
+
+    def test_none_returns_default(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration(None, 5.0) == 5.0
+
+    def test_string_number(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration("4.2", 1.0) == 4.2
+
+    def test_invalid_string_returns_default(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration("abc", 5.0) == 5.0
+
+    def test_negative_returns_default(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration(-1.0, 5.0) == 5.0
+
+    def test_zero_returns_default(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration(0, 5.0) == 5.0
+
+    def test_integer_value(self):
+        from app.api.routes.templates_editor.clips import _safe_segment_duration
+
+        assert _safe_segment_duration(10, 1.0) == 10.0
+