[core] Decorators are not added onto the anonymous type via metadata syntax

[ArcturusZhang]

If we have this:

model Foo {
  p: {
    a: string;
  };

we have the following syntax to add decorators to the anonymous model:

@@clientName(Foo.p::type, "NewName");

but in its type graph, the anonymous type never gets that decorator. And therefore it does not work at all.
Playground

[timotheeguerin]

This is by design, you cannot augment expressions that cannot be decorated to start with, this actually is now an error instead of silently failing https://cadlplayground.z22.web.core.windows.net/?c=CgpAc2VydmljZQpuYW1lc3BhY2UgQTsKCm1vZGVsIEZvbyB7CiAgcDrFByAgYTogc3RyaW5nOwogIH07Cn0KCkBAZG9jKEZvby5wOjp0eXBlLCAiUFAiKTvLG8UTxBQ%3D&e=%40typespec%2Fopenapi3&options=%7B%7D

[ArcturusZhang]

@timotheeguerin do we still have a way to get the declaration of anonymous models so that we could use client name to change their names?
This is a real requirement from customers (openai).
They do not want to change the spec to define models as named-models because they do not want the generated swagger to change, but they also want the generated client to have friendly names.

[timotheeguerin]

No it's not possible.

You have to change the spec here. They wrote garbage, it's not the job of the client.tsp to patch the garbage

[markcowl]

@schaabs Per discussion, please provide an example where this was previously working to add documentation in the emitted client for the OpenAI spec. Right now, we don't understand how this would have worked, so specifics are important to finding the underlying issue.

[timotheeguerin]

repro i used, all teh way back to 0.45.0

model Foo {
  a: {
    b: string;
  };
}

@@doc(Foo.a::type, "Doc here");

import { getDoc } from "@typespec/compiler";

export function $onEmit(context) {
  const namespace = context.program.getGlobalNamespaceType();
  const type = namespace.models.get("Foo").properties.get("a").type;

  console.log("type doc", getDoc(context.program, type));
  console.log("Decorators on type", type.decorators);
}

logs

TypeSpec compiler v0.45.0

type doc undefined
Decorators on type []
Compilation completed successfully.

you can see that the decorator is not even added

[ArcturusZhang]

@timotheeguerin FYI this is where the request was initially raised and resolved: Azure/typespec-azure#1094
It is closed and according to the playground link in the last comment from allen, it was working properly.

[timotheeguerin]

Yeah, you can augment the properties but not the model expression itself. The reason is you can put a decorator on the properties in the syntax but not on the expression so the same restriction applies to augment.
See the feature request for this #4927 this is basically at this point a dup)

[markcowl]

Closing in favor of #4927