fix: harden mirror material rebuild (empty/invalid frames, dedup, observability)

tests/unit/test_adversarial_mirror.py

@@ -2,7 +2,20 @@
 
 import pytest
 
-from app.question_gen.adversarial_filter import generate_mirror_question
+from app.question_gen.adversarial_filter import (
+    _rebuild_material,
+    generate_mirror_question,
+)
+from app.tree.index import (
+    IndexMeta,
+    L1Card,
+    L1Node,
+    L2Card,
+    L2Node,
+    L3Card,
+    L3Node,
+    TreeIndex,
+)
 from core.types import GeneratedQuestion, LLMResponse
 
 
@@ -73,3 +86,90 @@ async def test_mirror_malformed_response_returns_none():
 class _FakeMaterial:
     subtitle_sentences = ["先炒后蒸"]
     frame_paths = ["/f1.jpg"]
+
+
+class _NoCallVLM:
+    """素材为空时被误调用即失败——断言空素材绝不触达 VLM。"""
+
+    async def chat_with_images(self, *args, **kwargs):
+        raise AssertionError("素材为空时不应调用 VLM")
+
+
+class _EmptyMaterial:
+    subtitle_sentences: list[str] = []
+    frame_paths = ["/does/not/exist/frame_x.jpg"]
+
+
+@pytest.mark.asyncio
+async def test_mirror_empty_material_skips_vlm():
+    # 无字幕 AND 帧全不存在 → 直接返 None，且绝不调用 VLM
+    mirror = await generate_mirror_question(
+        _q(), flip_axis="before/after", vlm=_NoCallVLM(),
+        material=_EmptyMaterial(), session_id="s",
+    )
+    assert mirror is None
+
+
+def _tiny_tree() -> tuple[TreeIndex, str, str]:
+    """构建 1×L1→1×L2→2×L3 的最小真实树；返回 (tree, l2_id, first_l3_id)。
+
+    L2 自带字幕，两个 L3 各带字幕与帧路径，便于验证父子重叠去重。
+    """
+    l3_nodes = [
+        L3Node(
+            id=f"l2a_l3_{i}",
+            card=L3Card(
+                frame_summary=f"帧{i}",
+                visible_entities=[],
+                ongoing_actions=[],
+                visible_text=[],
+                spatial_layout="居中",
+                visual_attributes={},
+                subtitle=f"字幕{i}",
+            ),
+            frame_path=f"frames/l2a_l3_{i}.jpg",
+        )
+        for i in range(2)
+    ]
+    l2 = L2Node(
+        id="l2a",
+        card=L2Card(
+            event_description="事件A",
+            entities=[],
+            actions=[],
+            action_subjects=[],
+            visible_text=[],
+            spatial_relations="并列",
+            state_changes=None,
+            subtitle="L2字幕",
+        ),
+        children=l3_nodes,
+    )
+    l1 = L1Node(
+        id="l1a",
+        card=L1Card(
+            scene_summary="场景A",
+            main_setting="室内",
+            key_entities=[],
+            main_actions=[],
+            topic_keywords=[],
+            visible_text=[],
+            temporal_flow="顺序",
+        ),
+        children=[l2],
+    )
+    tree = TreeIndex(
+        metadata=IndexMeta(source_path="/t.mp4", modality="video"), roots=[l1]
+    )
+    return tree, "l2a", "l2a_l3_0"
+
+
+def test_rebuild_material_dedup_parent_child():
+    # source_nodes 同含父 L2 与子 L3（子树重叠）→ 素材须保序去重、无冗余
+    tree, l2_id, l3_id = _tiny_tree()
+    material = _rebuild_material(tree, (l2_id, l3_id))
+    assert len(material.subtitle_sentences) == len(set(material.subtitle_sentences))
+    assert len(material.frame_paths) == len(set(material.frame_paths))
+    # L2字幕 + 两条 L3 字幕 = 3 条；两帧 = 2 帧（去重后）
+    assert material.subtitle_sentences == ["L2字幕", "字幕0", "字幕1"]
+    assert material.frame_paths == ["frames/l2a_l3_0.jpg", "frames/l2a_l3_1.jpg"]