fix(generic): support variadic method invocation via generic call

[mochengqian]

Description

Fixes issue #3259
注意:本次PR为短期方案,但是已经可以关闭issue #3259

背景
Java 客户端通过泛化调用（$invoke）访问 Go 服务端定义了变长参数（...T）的方法时，
框架会触发 reflect.Value.Call panic，导致调用 100% 失败(测试见issue的comment)。

根因

两层问题叠加：

1. service_filter.go 参数数量校验过严 — argsType 中变长参数被记录为单个切片类型
   （如 []string），但 Java 端可能以离散形式发送多个 args，
   len(args) != len(argsType) 直接拒绝
2. callLocalMethod 使用 reflect.Value.Call() — 即使参数数量对齐，
   已打包为切片的变长参数传入 Call() 时会因类型不匹配触发
   panic: cannot use []string as type string in Call

修复方案

采用统一数组传参 + CallSlice 动态类型重塑策略，改动封锁在框架内部，
对外部业务代码零侵入：

文件	改动
common/rpc_service.go	MethodType 新增 IsVariadic() 方法，暴露变长方法元信息
filter/generic/service_filter.go	识别变长方法后，将 Java 传来的离散 args 或数组 args 通过 reflect.MakeSlice 重塑为精确类型切片
proxy/proxy_factory/utils.go	变长方法且尾参数为切片时使用 CallSlice 替代 Call
proxy/proxy_factory/default.go	variadic 分支优先于 []interface{} passthrough 检测，避免 ...interface{} 被错误多包一层

支持 Java 端两种传参形式：

• Form A（离散传参）：args: ["a", "b"] — 框架自动收拢为切片
• Form B（数组传参）：args: [["a", "b"]] — 框架自动解包内层数组

用户现在怎么调用:

Java 泛化调用 Go variadic 方法，两种传参方式都支持了：

方式 A：离散传参
genericService.$invoke(
"MultiArgs",
new String[]{"java.lang.String", "java.lang.String"},
new Object[]{"a", "b"}
);

方式 B：数组传参（推荐）
genericService.$invoke(
"MultiArgs",
new String[]{"[Ljava.lang.String;"},
new Object[]{new String[]{"a", "b"}}
);

非泛化调用也正常工作，Java 端按普通方法调用即可。

边界条件处理

场景	行为
零变长参数（空数组/未传参数）	构造长度为 0 的空切片，不 panic
单变长参数	正常投递，不误解析为多重嵌套
...interface{} 混合类型	直接接受任何值，不做强转
固定参数 + 变长参数混合	固定部分走常规 Realize，尾部进入变长重塑
显式 nil 注入	等同于零参数调用，不解引用 panic

Checklist

• I confirm the target branch is develop
• Code has passed local testing
• I have added tests that prove my fix is effective or that my feature works

[codecov-commenter]

Codecov Report

❌ Patch coverage is 61.73285% with 106 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.68%. Comparing base (60d1c2a) to head (06bbd4e).
⚠️ Report is 767 commits behind head on develop.

Files with missing lines	Patch %	Lines
filter/generic/service_filter.go	57.73%	68 Missing and 14 partials ⚠️
protocol/triple/server.go	64.86%	9 Missing and 4 partials ⚠️
proxy/proxy_factory/default.go	76.19%	2 Missing and 3 partials ⚠️
server/server.go	76.47%	2 Missing and 2 partials ⚠️
common/rpc_service.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3284      +/-   ##
===========================================
+ Coverage    46.76%   49.68%   +2.91%     
===========================================
  Files          295      469     +174     
  Lines        17172    34841   +17669     
===========================================
+ Hits          8031    17310    +9279     
- Misses        8287    16124    +7837     
- Partials       854     1407     +553     

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[AlexStocks]

Code review

[AlexStocks]

Additional code review

[AlexStocks]

Additional suggestions

[AlexStocks]

Please attention that your PR target branch should be develop.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR fixes generic ($invoke) calls from Java into Go methods with variadic parameters (...T) by reshaping generic args into a typed slice and invoking the target method using reflect.CallSlice when appropriate, preventing reflect.Value.Call panics (issue #3259).

Changes:

• Expose variadic metadata via MethodType.IsVariadic().
• Update generic service filter to validate variadic arg counts and reshape trailing args into the correct typed slice.
• Update proxy invocation to prefer variadic handling and use CallSlice when the final argument is already a slice.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
common/rpc_service.go	Adds IsVariadic() to expose variadic method info.
filter/generic/service_filter.go	Validates variadic arg counts and reshapes variadic args into typed slices for invocation.
proxy/proxy_factory/utils.go	Uses CallSlice for pre-packed variadic slices to avoid reflection panics.
proxy/proxy_factory/default.go	Ensures variadic branch runs before []interface{} passthrough logic.

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
13.7% Duplication on New Code

See analysis details on SonarQube Cloud