[Bug]: Discrepancy in api-version parameter optionality when multi-client

[antkmsft]

Describe the bug

As per Azure/typespec-rust#849, after upgrading to tcgc 0.65.0, for multi-client Spector tests, tcgc now tells us that api-version client parameter is optional. But when it comes to operation, that same parameter is given to us by tcgc as not optional. Parameter is .onClient == true, and there is never a default value.

I think the fact that the api-version parameter is reported as optional on the client is a bug.

Before 0.65.0, api-version always had .optional == false - be it among the client params or the operation params.

Reproduction

Here are the related tsps:

• https://github.com/Azure/typespec-azure/tree/809771bf32e07793b8bcb3035dfd28afe06a2ee2/packages/azure-http-specs/specs/service/multi-service
• https://github.com/Azure/typespec-azure/tree/809771bf32e07793b8bcb3035dfd28afe06a2ee2/packages/azure-http-specs/specs/azure/resource-manager/multi-service

Checklist

• Follow our Code of Conduct
• Check that this issue is about the Azure libraries for typespec. For bug in the typespec language or core libraries file it in the TypeSpec repo
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.

[tadelesh]

It is an intentional change in this PR: #3806. For multiple services case, the client level API version seems not useable, since the underlying operations may have different API version. So TCGC just chose to make it optional. We need to revisit it.

[tadelesh]

I checked the operation parameters. I saw api-version parameter has the defaultApiVersion value. Am I miss sth. here?