[WIP] Fix issue with defining multiple explicit clients

[Copilot]

Fix multiple explicit clients with multiple services

Problem

The TypeSpec TypeScript emitter's getRLCClients function was experiencing errors when handling multiple services with explicit @client decorators. The error "Can not define multiple explicit clients with multiple services" was being thrown by an older version of TypeSpec Client Generator Core (TCGC).

Resolution

Issue resolved upstream - No code changes needed in autorest.typescript.

The validation error was fixed in TCGC version 0.63.0, which added support for:

• Multiple services with explicit @client decorators
• Single client from multiple services feature
• Proper handling of 1:1 and 1:N service-to-client mappings

Current Implementation Status

• Understand the problem and current implementation
• Analyze getRLCClients function behavior
• Verify tests pass with TCGC 0.63.0
• Run unit tests to ensure no regressions (311 tests passing)
• Document the resolution

Implementation Details

The getRLCClients function correctly:

• Creates one RLC client per service namespace
• Handles multiple @client decorators per service (deduplicates using Set)
• Supports the new TCGC array service feature
• Uses service names for RLC client names (not @client decorator names)

Test Results

✅ All 311 RLC unit tests passing
✅ Test "should get the @client client if each services have only one @client decorators" passing
✅ Test "should handle both 1:1 and 1:N mappings between @service and @client" passing

Conclusion

The issue was resolved by updating to TCGC 0.63.0. No changes to autorest.typescript code are required.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Can not define multiple explicit clients with multiple services</issue_title>
<issue_description>RLC case:
https://github.com/Azure/autorest.typescript/blob/main/packages/typespec-ts/test/unit/clientUtil.spec.ts#L78
https://github.com/Azure/autorest.typescript/blob/main/packages/typespec-ts/test/unit/clientUtil.spec.ts#L112

typespec:

import "@azure-tools/typespec-client-generator-core";
using Azure.ClientGenerator.Core;
    
@service
namespace MyService {
  @client({
    name: "MyClient",
    service: MyService
  })
  interface MyInterface {
    op1(): void
  }
}

@service
namespace MySecondService {
  @client({
    name: "MySecondClient",
    service: MySecondService
  })
  interface MySecondInterface {
    op1(): void
  }
}

error log:

</issue_description>

Comments on the Issue (you are @copilot in this section)

@v-jiaodi In order to make the nightly CI pass, temporarily skip these two cases. https://dev.azure.com/azure-sdk/public/_build/results?buildId=5707767&view=logs&j=d0d2a462-287f-51d5-e186-98b6b49f577f&t=262df625-0311-50e6-2e41-9dfcf83669de

• Fixes Can not define multiple explicit clients with multiple services #3664

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