Dangling type $ref in Schema

[t0yv0]

Hello!

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Issue details

As I am building an AWS codegen for a new Pulumi language I encountered a peculiarity that's not obvious.

curl https://raw.githubusercontent.com/pulumi/pulumi-aws/v4.37.3/provider/cmd/pulumi-resource-aws/schema.json -o ~/schemas/pulumi-aws-v4.37.3.json

jq '.resources["aws:iam/instanceProfile:InstanceProfile"].stateInputs.properties.role' ~/schemas/pulumi-aws-v4.37.3.json

{
  "type": "string",
  "oneOf": [
    {
      "type": "string"
    },
    {
      "type": "string",
      "$ref": "#/types/aws:iam/role:Role"
    }
  ],
  "description": "Name of the role to add to the profile.\n"
}

jq '.types["aws:iam/role:Role"]' ~/schemas/pulumi-aws-v4.37.3.json
null

jq '.resources["aws:iam/role:Role"].properties.uniqueId' ~/schemas/pulumi-aws-v4.37.3.json 
{
  "type": "string",
  "description": "Stable and unique string identifying the role.\n"
}

You may notice that the "$ref" in the example does not have a corresponding entry in the .types; it does have a corresponding entry in .resources though. I wonder if this is a mistake in the schema - should we catch these by the schema checker? Or something meaningful is intended here?

Also, if the reference was not dangling but the type was defined, I'm wondering what the form that uses both "type" and "$ref" signify. That seemed malformed and I could not find docs about this.

    {
      "type": "string",
      "$ref": "#/types/aws:iam/role:Role"
    }

The C# codegen simply deals with this as Input which is also what I can do, but it's confusing.

Steps to reproduce

Expected:
Actual:

[t0yv0]

OK I think this may be something slightly undocumented referred to as "relaxed enums". The form is relaxed enum form. Still I think the dangling ref is an error.

[mikhailshilkov]

This is tracked more broadly in #2565, I'll close this issue as a dupe