dubbo TagRouter does not work with dubbo:parameter

[sanjy523892105]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.1
• Operating System version: win10
• Java version: jdk1.8.0_101

Steps to reproduce this issue

1. 使用 dubbo-demo-xml 项目，或者其他测试项目
2. 启动两个provider示例，一个在 <dubbo:service/> 中加上tag="groupA" 我们叫他 p1，另一个不加tag 我们叫他 p2.
3. 在<dubbo:reference>标签中添加<dubbo:parameter key="dubbo.tag" value="groupA"/> 之后将consumer 示例启动

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1. use dubbo-demo-xml, or other demo .
2. prepare two providers, one set tag="groupA" at <dubbo:service/> called p1 , another with no tag called p2. start them.
3. start a consumer instance ,after set <dubbo:parameter key="dubbo.tag" value="groupA"/> inside of <dubbo:reference>.

Expected Result

因为拥有相同的tag声明，consumer本应该会调用到p1示例.
consumer would connect p1 because of the same tag definition

Actual Result

但consumer依然可能连接到p2示例.
consumer also connects p2.

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如果把 步骤3 的标签改为在调用代码中使用RpcContext.getContext().setAttachment("dubbo.tag","groupA"),是可以正常工作的。请问这两种方式有什么区别呢？

通过分析源码发现 在 RegistryDiscovery 中将consumer 端的parameter 整合到providerUrl 中。 请问为什么需要这步操作？

[chickenlj]

I test and both these two ways can work:
RpcContext.getContext().setAttachment("dubbo.tag","groupA") or <dubbo:parameter key="dubbo.tag" value="groupA"/>

[chickenlj]

Sorry <dubbo:parameter key="dubbo.tag" value="groupA"/> does have some problem, I just ran the wrong sample.