fix(serialization): load failure on hardened yaml-cpp + flow-style arrays

yaml-cpp master hardens zombie nodes: operator=, size(), Type() and
chained operator[] all throw InvalidNode instead of silently passing.
Storing per-component nodes via Node::operator= threw for every key
that was absent, so all 7 entities were skipped on load (0 loaded).
Reads are now level-by-level guarded (copy-init + IsDefined), which
only uses the safe surface (as<T>(fallback), begin(), IsDefined).

Save side switched from node-tree streaming to a manual Emitter:
vector/quat fields emit as single-line flow arrays ([0, 1.2, -6])
and model refs as inline maps, with 9-digit float precision for
lossless float32 round-trips.

Verified offline against the previously saved scene: 7/7 entities
parse with correct component counts; emitter output round-trips.

Engine/src/Serialization/SceneSerializer.cpp

@@ -1,10 +1,18 @@
 //
 // Created by atdunbg on 2026/10/3.
 //
-// SceneSerializer：场景 ↔ YAML。结构见头文件注释与计划 v3。
+// SceneSerializer：场景 ↔ YAML。结构见头文件注释。
 //
-// 原子性：Deserialize 先把整个文件解析进中间结构（逐实体容错），
-// 全部成功才 scene.Clear() 换血重建——解析失败不动现场。
+// 写端：手动 Emitter 逐键输出（短集合用 Flow 单行数组/内联 map，
+// 浮点 9 位精度保证 float32 无损往返）。
+// 读端：yaml-cpp 新版对"僵尸节点"（缺失键的返回值）硬化——operator=、
+// size()、Type()、链式 operator[] 一律抛 InvalidNode，只有 IsDefined/
+// as<T>(fallback)/begin() 安全。因此读侧铁律：每层节点先
+// `const Node n = parent["Key"]` 拷贝初始化 + `if (n)` 判空再访问，
+// 绝不对可能缺失的键做赋值或链式下标。
+//
+// 原子性：Deserialize 先解析到中间结构（逐实体容错），全部成功才
+// scene.Clear() 换血重建——解析失败不动现场。
 //
 
 #include <Engine/Serialization/SceneSerializer.h>
@@ -32,18 +40,33 @@ namespace Engine::Serialization {
 
     namespace {
 
-        // ---- 写出辅助：glm → 数组 ----
+        // ---- 写端辅助：Flow 单行数组（Position: [0, 1.2, -6]）----
 
-        std::vector<f32> Vec3Arr(const glm::vec3& v) { return {v.x, v.y, v.z}; }
-        std::vector<f32> Vec4Arr(const glm::vec4& v) { return {v.x, v.y, v.z, v.w}; }
-        std::vector<f32> QuatArr(const glm::quat& q) { return {q.w, q.x, q.y, q.z}; }
+        void EmitVec3(YAML::Emitter& e, const glm::vec3& v)
+        {
+            e << YAML::Flow << YAML::BeginSeq << v.x << v.y << v.z
+              << YAML::EndSeq;
+        }
 
-        // ---- 读入辅助：缺字段/类型错 → 默认值（as<T>(fallback) 语义）----
+        void EmitVec4(YAML::Emitter& e, const glm::vec4& v)
+        {
+            e << YAML::Flow << YAML::BeginSeq << v.x << v.y << v.z << v.w
+              << YAML::EndSeq;
+        }
+
+        void EmitQuat(YAML::Emitter& e, const glm::quat& q)
+        {
+            e << YAML::Flow << YAML::BeginSeq << q.w << q.x << q.y << q.z
+              << YAML::EndSeq;
+        }
+
+        // ---- 读端辅助：缺字段/类型错/僵尸节点 → 默认值 ----
 
         glm::vec3 ReadVec3(const YAML::Node& n, const glm::vec3& def)
         {
             if (!n || !n.IsSequence() || n.size() < 3) return def;
-            return {n[0].as<f32>(def.x), n[1].as<f32>(def.y), n[2].as<f32>(def.z)};
+            return {n[0].as<f32>(def.x), n[1].as<f32>(def.y),
+                    n[2].as<f32>(def.z)};
         }
 
         glm::vec4 ReadVec4(const YAML::Node& n, const glm::vec4& def)
@@ -144,103 +167,120 @@ namespace Engine::Serialization {
             return ref;
         }
 
-        // 资产引用双写：{Guid, Path}（procedural 只有 Path，Guid=0 不写）
-        void WriteModelRef(YAML::Node& node, Assets::AssetManager& assets,
-                           ModelRef ref)
-        {
-            const std::string& path = assets.Models().Path(ref);
-            if (path.empty()) {
-                ENGINE_WARN("SceneSerializer: entity has invalid model ref, "
-                            "MeshRenderer skipped");
-                return;
-            }
-            YAML::Node m;
-            if (const u64 guid = assets.GetOrCreateGUID(path); guid != 0) {
-                m["Guid"] = guid;
-            }
-            m["Path"] = path;
-            node["Model"] = m;
-        }
-
         // ---- 中间结构：解析全部成功才碰 registry ----
+        // comps 持 Components 节点（仅在键存在且为 map 时赋值——
+        // yaml-cpp 新版对僵尸节点做 operator= 会抛异常）
 
         struct ParsedEntity
         {
             u64 uuid = 0;
             std::string name = "entity";
-            YAML::Node transform, meshRenderer, animation, camera, light,
-                rigidBody;   // 未出现 = undefined
+            YAML::Node comps;   // 缺省 = Null（无组件）
         };
 
-        void SerializeEntity(YAML::Node& out, Assets::AssetManager& assets,
+        // 写端：单实体 → Emitter（调用方已进入 Entities 序列）
+        void EmitEntity(YAML::Emitter& out, Assets::AssetManager& assets,
                         const ECS::Registry& reg, entt::entity e)
         {
             const auto& id = reg.get<ECS::IdComponent>(e);
 
-            YAML::Node ent;
-            ent["Entity"] = id.uuid.Value();
+            out << YAML::BeginMap;
+            out << YAML::Key << "Entity" << YAML::Value << id.uuid.Value();
             if (const auto* name = reg.try_get<ECS::NameComponent>(e)) {
-                ent["Name"] = name->name;
+                out << YAML::Key << "Name" << YAML::Value << name->name;
             }
 
-            YAML::Node comps;
+            out << YAML::Key << "Components" << YAML::Value << YAML::BeginMap;
 
             if (const auto* t = reg.try_get<ECS::TransformComponent>(e)) {
-                YAML::Node n;
-                n["Position"] = Vec3Arr(t->GetPosition());
-                n["Rotation"] = QuatArr(t->GetRotationQuat());   // (w,x,y,z) 无损
-                n["Scale"] = Vec3Arr(t->GetScale());
-                comps["Transform"] = n;
+                out << YAML::Key << "Transform" << YAML::Value
+                    << YAML::BeginMap;
+                out << YAML::Key << "Position" << YAML::Value;
+                EmitVec3(out, t->GetPosition());
+                out << YAML::Key << "Rotation" << YAML::Value;
+                EmitQuat(out, t->GetRotationQuat());   // (w,x,y,z) 无损
+                out << YAML::Key << "Scale" << YAML::Value;
+                EmitVec3(out, t->GetScale());
+                out << YAML::EndMap;
             }
 
             if (const auto* mr = reg.try_get<ECS::MeshRendererComponent>(e)) {
-                YAML::Node n;
-                WriteModelRef(n, assets, mr->model);
-                if (const YAML::Node m = n["Model"]) comps["MeshRenderer"] = n;
+                // ModelRef → {Guid, Path}：Path 反查为空 = 无效引用，跳过
+                const std::string& path = assets.Models().Path(mr->model);
+                if (!path.empty()) {
+                    out << YAML::Key << "MeshRenderer" << YAML::Value
+                        << YAML::BeginMap;
+                    out << YAML::Key << "Model" << YAML::Value << YAML::Flow
+                        << YAML::BeginMap;
+                    if (const u64 guid = assets.GetOrCreateGUID(path);
+                        guid != 0) {
+                        out << YAML::Key << "Guid" << YAML::Value << guid;
+                    }
+                    out << YAML::Key << "Path" << YAML::Value << path;
+                    out << YAML::EndMap;   // Model（flow）
+                    out << YAML::EndMap;   // MeshRenderer
+                }
+                else {
+                    ENGINE_WARN("SceneSerializer: entity has invalid model "
+                                "ref, MeshRenderer skipped");
+                }
             }
 
             if (const auto* a = reg.try_get<ECS::AnimationComponent>(e)) {
-                YAML::Node n;
-                n["ClipIndex"] = a->clipIndex;
-                n["Playing"] = a->playing;
-                n["Loop"] = a->loop;
-                n["Speed"] = a->speed;   // fade*/time 是运行态，不存
-                comps["Animation"] = n;
+                out << YAML::Key << "Animation" << YAML::Value << YAML::Flow
+                    << YAML::BeginMap;
+                out << YAML::Key << "ClipIndex" << YAML::Value << a->clipIndex;
+                out << YAML::Key << "Playing" << YAML::Value << a->playing;
+                out << YAML::Key << "Loop" << YAML::Value << a->loop;
+                out << YAML::Key << "Speed" << YAML::Value << a->speed;
+                out << YAML::EndMap;
             }
 
             if (const auto* c = reg.try_get<ECS::CameraComponent>(e)) {
-                YAML::Node n;
-                n["Primary"] = c->primary;   // 相机不存投影参数（调用方传入）
-                comps["Camera"] = n;
+                out << YAML::Key << "Camera" << YAML::Value << YAML::Flow
+                    << YAML::BeginMap;
+                out << YAML::Key << "Primary" << YAML::Value << c->primary;
+                out << YAML::EndMap;
             }
 
             if (const auto* l = reg.try_get<ECS::LightComponent>(e)) {
-                YAML::Node n;
-                n["Type"] = static_cast<u8>(l->type);
-                n["Direction"] = Vec3Arr(l->direction);
-                n["Color"] = Vec4Arr(l->color);
-                n["Radius"] = l->radius;
-                n["CastShadow"] = l->castShadow;
-                comps["Light"] = n;
+                out << YAML::Key << "Light" << YAML::Value << YAML::BeginMap;
+                out << YAML::Key << "Type" << YAML::Value
+                    << static_cast<int>(l->type);
+                out << YAML::Key << "Direction" << YAML::Value;
+                EmitVec3(out, l->direction);
+                out << YAML::Key << "Color" << YAML::Value;
+                EmitVec4(out, l->color);
+                out << YAML::Key << "Radius" << YAML::Value << l->radius;
+                out << YAML::Key << "CastShadow" << YAML::Value
+                    << l->castShadow;
+                out << YAML::EndMap;
             }
 
             if (const auto* rb = reg.try_get<ECS::RigidBodyComponent>(e)) {
-                YAML::Node n;
-                n["Type"] = static_cast<u8>(rb->type);
-                n["Collider"] = static_cast<u8>(rb->collider);
-                n["BoxHalfExtents"] = Vec3Arr(rb->boxHalfExtents);
-                n["SphereRadius"] = rb->sphereRadius;
-                n["Mass"] = rb->mass;
-                n["GravityScale"] = rb->gravityScale;
-                n["Friction"] = rb->friction;
-                n["Restitution"] = rb->restitution;
-                n["IsSensor"] = rb->isSensor;
+                out << YAML::Key << "RigidBody" << YAML::Value
+                    << YAML::BeginMap;
+                out << YAML::Key << "Type" << YAML::Value
+                    << static_cast<int>(rb->type);
+                out << YAML::Key << "Collider" << YAML::Value
+                    << static_cast<int>(rb->collider);
+                out << YAML::Key << "BoxHalfExtents" << YAML::Value;
+                EmitVec3(out, rb->boxHalfExtents);
+                out << YAML::Key << "SphereRadius" << YAML::Value
+                    << rb->sphereRadius;
+                out << YAML::Key << "Mass" << YAML::Value << rb->mass;
+                out << YAML::Key << "GravityScale" << YAML::Value
+                    << rb->gravityScale;
+                out << YAML::Key << "Friction" << YAML::Value << rb->friction;
+                out << YAML::Key << "Restitution" << YAML::Value
+                    << rb->restitution;
+                out << YAML::Key << "IsSensor" << YAML::Value << rb->isSensor;
                 // bodyId/bodyValid/velocity 由 PhysicsWorld 对账重建，不存
-                comps["RigidBody"] = n;
+                out << YAML::EndMap;
             }
 
-            if (comps.size() > 0) ent["Components"] = comps;
-            out.push_back(ent);
+            out << YAML::EndMap;   // Components
+            out << YAML::EndMap;   // Entity
         }
 
     } // namespace
@@ -253,35 +293,50 @@ namespace Engine::Serialization {
                                     const std::string& environmentPath)
     {
         try {
-            YAML::Node root;
-            root["Scene"] = std::filesystem::path(outPath).stem().string();
-            root["Version"] = kSceneVersion;
+            // float32 无损往返需 9 位有效数字（std::numeric_limits
+            // <float>::max_digits10）
+            YAML::Emitter out;
+            out.SetFloatPrecision(9);
+
+            out << YAML::BeginMap;
+            out << YAML::Key << "Scene" << YAML::Value
+                << std::filesystem::path(outPath).stem().string();
+            out << YAML::Key << "Version" << YAML::Value << kSceneVersion;
             if (!environmentPath.empty()) {
-                root["Environment"] = environmentPath;
+                out << YAML::Key << "Environment" << YAML::Value
+                    << environmentPath;
             }
 
             const auto& s = scene.GetSettings();
-            YAML::Node st;
-            st["ClearColor"] = Vec4Arr(s.ClearColor);
-            st["AmbientColor"] = Vec4Arr(s.AmbientColor);
-            st["DrawSkybox"] = s.DrawSkybox;
-            root["Settings"] = st;
+            out << YAML::Key << "Settings" << YAML::Value << YAML::BeginMap;
+            out << YAML::Key << "ClearColor" << YAML::Value;
+            EmitVec4(out, s.ClearColor);
+            out << YAML::Key << "AmbientColor" << YAML::Value;
+            EmitVec4(out, s.AmbientColor);
+            out << YAML::Key << "DrawSkybox" << YAML::Value << s.DrawSkybox;
+            out << YAML::EndMap;
 
-            YAML::Node entities(YAML::NodeType::Sequence);
+            out << YAML::Key << "Entities" << YAML::Value << YAML::BeginSeq;
             const ECS::Registry& reg = scene.GetRegistry();
             reg.view<ECS::IdComponent>().each(
                 [&](entt::entity e, const ECS::IdComponent&) {
-                    SerializeEntity(entities, assets, reg, e);
+                    EmitEntity(out, assets, reg, e);
                 });
-            root["Entities"] = entities;
+            out << YAML::EndSeq;
+            out << YAML::EndMap;
 
-            std::ofstream out(outPath, std::ios::trunc);
-            if (!out) {
+            if (!out.good()) {
+                ENGINE_ERROR("SceneSerializer: emit failed: {}", out.GetLastError());
+                return false;
+            }
+
+            std::ofstream file(outPath, std::ios::trunc);
+            if (!file) {
                 ENGINE_ERROR("SceneSerializer: cannot open '{}' for write",
                              outPath);
                 return false;
             }
-            out << root;
+            file << out.c_str();
             return true;
         }
         catch (const YAML::Exception& e) {
@@ -326,6 +381,7 @@ namespace Engine::Serialization {
             return false;
         }
 
+        // 僵尸节点安全：as<T>(fallback) 对缺失键返回 fallback
         outEnvironmentPath = root["Environment"].as<std::string>("");
 
         if (const YAML::Node st = root["Settings"]; st && st.IsMap()) {
@@ -339,7 +395,7 @@ namespace Engine::Serialization {
         std::vector<ParsedEntity> parsed;
 
         const YAML::Node entities = root["Entities"];
-        if (entities.IsSequence()) {
+        if (entities && entities.IsSequence()) {
             parsed.reserve(entities.size());
             for (const auto& e : entities) {
                 try {
@@ -348,13 +404,8 @@ namespace Engine::Serialization {
                     pe.name = e["Name"].as<std::string>(pe.name);
                     if (const YAML::Node comps = e["Components"];
                         comps && comps.IsMap()) {
-                        pe.transform = comps["Transform"];
-                        pe.meshRenderer = comps["MeshRenderer"];
-                        pe.animation = comps["Animation"];
-                        pe.camera = comps["Camera"];
-                        pe.light = comps["Light"];
-                        pe.rigidBody = comps["RigidBody"];
-                        // 未识别的组件键自然跳过（前向兼容）
+                        // 仅在 rhs 有效时赋值（僵尸节点 operator= 会抛）
+                        pe.comps = comps;
                     }
                     parsed.push_back(std::move(pe));
                 }
@@ -380,18 +431,19 @@ namespace Engine::Serialization {
             }
             handle.GetComponent<ECS::IdComponent>().uuid = UUID{uuid};
 
-            if (pe.transform) {
-                const YAML::Node n = pe.transform;
+            const YAML::Node comps = pe.comps;   // 拷贝初始化，缺省 Null
+
+            if (const YAML::Node n = comps["Transform"]) {
                 auto& t = handle.GetComponent<ECS::TransformComponent>();
                 t.SetPosition(ReadVec3(n["Position"], t.GetPosition()));
                 t.SetRotationQuat(ReadQuat(n["Rotation"]));
                 t.SetScale(ReadVec3(n["Scale"], t.GetScale()));
             }
 
-            if (pe.meshRenderer) {
-                const YAML::Node n = pe.meshRenderer;
-                const u64 guid = n["Model"]["Guid"].as<u64>(0);
-                const auto path = n["Model"]["Path"].as<std::string>("");
+            if (const YAML::Node n = comps["MeshRenderer"]) {
+                if (const YAML::Node m = n["Model"]) {
+                    const u64 guid = m["Guid"].as<u64>(0);
+                    const auto path = m["Path"].as<std::string>("");
                     if (ModelRef ref = ResolveModel(assets, guid, path);
                         ref.Valid()) {
                         handle.AddComponent<ECS::MeshRendererComponent>(
@@ -399,13 +451,14 @@ namespace Engine::Serialization {
                     }
                     else {
                         ENGINE_WARN("SceneSerializer: model unresolved "
-                                "(guid={}, path='{}'), MeshRenderer skipped",
+                                    "(guid={}, path='{}'), MeshRenderer "
+                                    "skipped",
                                     guid, path);
                     }
                 }
+            }
 
-            if (pe.animation) {
-                const YAML::Node n = pe.animation;
+            if (const YAML::Node n = comps["Animation"]) {
                 auto& a = handle.AddComponent<ECS::AnimationComponent>();
                 a.clipIndex = n["ClipIndex"].as<int>(a.clipIndex);
                 a.playing = n["Playing"].as<bool>(a.playing);
@@ -413,16 +466,15 @@ namespace Engine::Serialization {
                 a.speed = n["Speed"].as<f32>(a.speed);
             }
 
-            if (pe.camera) {
-                const YAML::Node n = pe.camera;
+            if (const YAML::Node n = comps["Camera"]) {
                 auto& c = handle.AddComponent<ECS::CameraComponent>();
                 c.primary = n["Primary"].as<bool>(false);
             }
 
-            if (pe.light) {
-                const YAML::Node n = pe.light;
+            if (const YAML::Node n = comps["Light"]) {
                 auto& l = handle.AddComponent<ECS::LightComponent>();
-                if (const u8 type = n["Type"].as<u8>(0); type <= 1) {
+                if (const int type = n["Type"].as<int>(0); type >= 0 &&
+                                                           type <= 1) {
                     l.type = static_cast<ECS::LightComponent::Type>(type);
                 }
                 l.direction = ReadVec3(n["Direction"], l.direction);
@@ -431,14 +483,15 @@ namespace Engine::Serialization {
                 l.castShadow = n["CastShadow"].as<bool>(l.castShadow);
             }
 
-            if (pe.rigidBody) {
-                const YAML::Node n = pe.rigidBody;
+            if (const YAML::Node n = comps["RigidBody"]) {
                 auto& rb = handle.AddComponent<ECS::RigidBodyComponent>();
-                if (const u8 type = n["Type"].as<u8>(0); type <= 2) {
-                    rb.type = static_cast<ECS::RigidBodyComponent::BodyType>(
-                        type);
+                if (const int type = n["Type"].as<int>(0);
+                    type >= 0 && type <= 2) {
+                    rb.type =
+                        static_cast<ECS::RigidBodyComponent::BodyType>(type);
                 }
-                if (const u8 col = n["Collider"].as<u8>(0); col <= 2) {
+                if (const int col = n["Collider"].as<int>(0);
+                    col >= 0 && col <= 2) {
                     rb.collider =
                         static_cast<ECS::RigidBodyComponent::ColliderType>(
                             col);