[tcgc] provide a name for SDK client (when SDK client is from TypeSpec Namespace)

[weidongxu-microsoft]

Clear and concise description of the problem

Context

For unbranded or simple Azure (without @client in client.tsp), the name of the Namespace becomes the name of the client

namespace Client {
  interface SubClient {
  }
}

TypeSpec for Azure management mostly uses this pattern.

However, the namespace provided by service usually is not a good candidate for SDK client.
Service typically use ARM RP namespace as TypeSpec Namespace. e.g. Microsoft.DocumentDB, while SDK want to use a more meaningful client named like MongoClusterMgmtClient.

Currently, dev usually did a @clientName on the namespace to modify the name of the client.

But given the new namespace design, this same @clientName syntax now modify the SDK namespace (instead of SDK client name).

In short, after namespace design, the TypeSpec Namespace specifies both the SDK namespace AND SDK client name. And @clientName can only modify one of the two.

Proposal

Have a new decorator to specify the name of the client to the Namespace. The name of the decorator is TBD.

Alternatives Considered

Write a full client.tsp client hierarchy

Con:

• With current client hierarchy design with @client @operationGroup decorators, dev had to write the full @client @operationGroup in client.tsp, which typically results to hundreds of lines in client.tsp. And service had to add more to it, whenever they add new Interface/Resource to main.tsp

Use title in @service for ARM mgmt

There is a title in @service, which maps to title in Swagger.

Con:

• It does not fit our current client hierarchy design.
• It won't work for nested Namespace e.g. namespace Client { namespace SubClent {...} }
• If we really do this, we probably limit this for ARM MGMT.

Repurpose the @client decorator so that it can apply to service Namespace and provide an SDK name

@@client(ServiceNamespace, {name: "<sdk-client-name>"})

Con:

• Same, it does not exactly fit our current client hierarchy design.
• The slightly different application of same @client could be confusing to dev.

Checklist

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

[weidongxu-microsoft]

close, as decision be adding a different @clientNamespace decorator for namespace.