Support returning plain values from .NET methods

[t0yv0]

Hello!

• Vote on this issue by adding a 👍 reaction
• If you want to implement this feature, comment to let us know (we'll work with you on design, scheduling, etc.)

Issue details

As a provider author I would like to be able to mark methods as plain: true so that my provider's consumers can access their results directly without an Output wrapper.

Further, methods that return a single value only should not be wrapped in a struct, making it as simple as possible to consume.

Methods should be able to return explicit Provider references usable for configuring other resources in the stack, so that methods can be used as factories to simplify complex provider configuration.

Here is a PR implementing plain-valued methods for Node, Python, Go that includes acceptance tests for this feature:
pulumi/pulumi#13592

Borrowing from that PR, the new schema forms is listed below; "tlsProvider" returns a singleton provider reference, "meaningOfLife" returns a singleton integer, and "objectMix" returns both in a struct.

  "functions": {
    "metaprovider:index:Configurer/tlsProvider": {
      "inputs": {
        "properties": {
          "__self__": {
            "$ref": "#/resources/metaprovider:index:Configurer"
          }
        }
      },
      "outputs": {
        "$ref": "/tls/v4.10.0/schema.json#/provider",
        "plain": true
      }
    },
    "metaprovider:index:Configurer/meaningOfLife": {
      "inputs": {
        "properties": {
          "__self__": {
            "$ref": "#/resources/metaprovider:index:Configurer"
          }
        }
      },
      "outputs": {
        "type": "integer",
        "plain": true
      }
    },
    "metaprovider:index:Configurer/objectMix": {
      "inputs": {
        "properties": {
          "__self__": {
            "$ref": "#/resources/metaprovider:index:Configurer"
          }
        }
      },
      "outputs": {
        "type": "object",
        "plain": true,
        "properties": {
          "provider": {
            "$ref": "/tls/v4.10.0/schema.json#/provider"
          },
          "meaningOfLife": {
            "type": "integer"
          }
        }
      }
    }
  },

Affected area/feature