fix: 统一封面管道增加cover_url多步fallback查找，修复500错误

根因：统一封面管道只通过 generation_task_id 查找 cover_url，但 generation_task_id 为空时（如 plan 创建时未关联），直接 fall through 到 run_generate_cover → RuntimeError → 500。修复： - 统一封面管道 section 增加与视频URL查找一致的 3 步 fallback: A: generation_task_id 直接查找 B: source_edit_plan_id 查找 C: user+template 兜底查找 - 所有步骤都找不到 cover_url 时返回 400 而非 500，提示用户重新生成预览视频以触发封面自动提取 - 新增 3 个单元测试覆盖新 fallback 路径
2026-08-15 11:30:52 +08:00
parent 206d517a91
commit 8b1be55f9d
2 changed files with 225 additions and 60 deletions
@@ -209,39 +209,101 @@ def generate_cover(
        ) from e

    # 统一封面管道：优先从 GenerationTask.cover_url 读取渲染后视频抽帧的封面
+    # 多步查找 cover_url，和查找视频 URL 一样的 fallback 逻辑
    if body.cover_type in ("ai_frame", "ai_regenerate"):
-        # 尝试从 GenerationTask 读取已持久化的封面 URL
+        cover_url_from_task = None
+        gen_task_repo = SQLAlchemyGenerationTaskRepository(db)
+
+        # 步骤 A：通过 generation_task_id 直接查找
        generation_task_id = (plan.config or {}).get("generation_task_id", "")
        if generation_task_id:
            try:
-                gen_task_repo = SQLAlchemyGenerationTaskRepository(db)
                task = gen_task_repo.get(generation_task_id)
                if task and getattr(task, "cover_url", ""):
-                    cover_data = {
-                        "type": "ai_frame",
-                        "image_url": task.cover_url,
-                        "frame_time": 0.0,
-                        "confidence": 0.95,
-                    }
+                    cover_url_from_task = task.cover_url
                    logger.info(
-                        "[封面生成] 使用统一管道封面: plan_id=%s task_id=%s url=%s",
+                        "[封面生成] 统一管道封面(步骤A-direct): plan_id=%s task_id=%s url=%s",
                        plan_id,
                        generation_task_id,
-                        task.cover_url[:80],
+                        cover_url_from_task[:80],
                    )
-                    current_config = dict(plan.config) if plan.config else {}
-                    current_config["cover"] = cover_data
-                    normalized = normalize_plan_config(current_config)
-                    plan_svc.update_plan_config(plan_id, {"cover": normalized["cover"]})
-                    return GenerateCoverResponse(plan_id=plan_id, cover=cover_data)
            except Exception:
                logger.warning(
-                    "[封面生成] 读取 GenerationTask.cover_url 失败: plan_id=%s task_id=%s",
+                    "[封面生成] 步骤A读取 cover_url 失败: plan_id=%s task_id=%s",
                    plan_id,
                    generation_task_id,
                    exc_info=True,
                )

+        # 步骤 B：通过 source_edit_plan_id 查找关联预览任务的 cover_url
+        if not cover_url_from_task:
+            try:
+                preview_tasks = gen_task_repo.list_by_source_edit_plan(plan_id)
+                for pt in preview_tasks:
+                    if getattr(pt, "status", "") == "completed" and getattr(pt, "cover_url", ""):
+                        cover_url_from_task = pt.cover_url
+                        logger.info(
+                            "[封面生成] 统一管道封面(步骤B-source_plan): plan_id=%s task_id=%s url=%s",
+                            plan_id,
+                            pt.id,
+                            cover_url_from_task[:80],
+                        )
+                        break
+            except Exception:
+                logger.warning(
+                    "[封面生成] 步骤B查找 cover_url 失败: plan_id=%s",
+                    plan_id,
+                    exc_info=True,
+                )
+
+        # 步骤 C：通过 user+template 查找最近的已完成预览任务的 cover_url
+        if not cover_url_from_task:
+            try:
+                preview_tasks = gen_task_repo.list_latest_completed_preview(
+                    user_id=str(current_user.user.id),
+                    template_id=template_id,
+                )
+                for pt in preview_tasks:
+                    if getattr(pt, "cover_url", ""):
+                        cover_url_from_task = pt.cover_url
+                        logger.info(
+                            "[封面生成] 统一管道封面(步骤C-user+template): plan_id=%s task_id=%s url=%s",
+                            plan_id,
+                            pt.id,
+                            cover_url_from_task[:80],
+                        )
+                        break
+            except Exception:
+                logger.warning(
+                    "[封面生成] 步骤C查找 cover_url 失败: plan_id=%s template_id=%s",
+                    plan_id,
+                    template_id,
+                    exc_info=True,
+                )
+
+        if cover_url_from_task:
+            cover_data = {
+                "type": "ai_frame",
+                "image_url": cover_url_from_task,
+                "frame_time": 0.0,
+                "confidence": 0.95,
+            }
+            current_config = dict(plan.config) if plan.config else {}
+            current_config["cover"] = cover_data
+            normalized = normalize_plan_config(current_config)
+            plan_svc.update_plan_config(plan_id, {"cover": normalized["cover"]})
+            return GenerateCoverResponse(plan_id=plan_id, cover=cover_data)
+
+        logger.warning(
+            "[封面生成] 统一管道未找到 cover_url: plan_id=%s",
+            plan_id,
+        )
+        # ai_frame/ai_regenerate 类型必须从渲染管道获取，不再回退到 AI 服务
+        raise HTTPException(
+            status_code=400,
+            detail="封面尚未生成，请先重新生成预览视频以触发封面自动提取",
+        )
+
    from packages.shared.ai_service import run_generate_cover

    try: