Nodejs codegen regression impacting Azure provider

[AaronFriel]

The Azure SDK generates invalid codegen for plain invokes such as azure:automation/getAccount:getAccount, returning Promise<void> instead of a return type.

Before:

export function getAccount(args: GetAccountArgs, opts?: pulumi.InvokeOptions): Promise<GetAccountResult> {
    if (!opts) {
        opts = {}
    }

    opts = pulumi.mergeOptions(utilities.resourceOptsDefaults(), opts);
    return pulumi.runtime.invoke("azure:storage/getAccount:getAccount", {
        "minTlsVersion": args.minTlsVersion,
        "name": args.name,
        "resourceGroupName": args.resourceGroupName,
    }, opts);
}

After:

export function getAccount(args: GetAccountArgs, opts?: pulumi.InvokeOptions): Promise<void> {

    opts = pulumi.mergeOptions(utilities.resourceOptsDefaults(), opts || {});
    return pulumi.runtime.invoke("azure:storage/getAccount:getAccount", {
        "minTlsVersion": args.minTlsVersion,
        "name": args.name,
        "resourceGroupName": args.resourceGroupName,
    }, opts);
}

The return type declaration GetAccountResult is also omitted.

This appears to be a regression introduced in #11418, determined by bisection.

[AaronFriel]

I was able to bisect pu/pu to a commit that had the issue, but couldn't reproduce the behavior with a synthetic schema. PR #11418 should be reverted because it introduces the breaking change, and before that PR is reintroduced, the breaking change to the schema should be addressed.

Notes on root causing:

Adding an unserialized ReturnType field on the schema.FunctionSpec type was a breaking change in the API contract with the tfgen bridge and any other tools that generate a PackageSpec directly (without marshaling/unmarshaling) before binding it and calling GeneratePackage.

In cd6f658 we can see that a regression test fails to catch this case, the generated code is correct and matches the "before" case! That's because the regression tests in Pulumi load schemas from JSON, so the ReturnType field is populated. That occurs in the implementation of unmarshalFunctionSpec at line 1656:

pulumi/pkg/codegen/schema/schema.go

Lines 1649 to 1658 in 78c9bf4

	if returnType, ok := data["outputs"]; ok {
	isEmpty, err := emptyObject(returnType)
	if err != nil {
	return err
	}
	if !isEmpty {
	if err := json.Unmarshal(returnType, &funcSpec.ReturnType); err != nil {
	return err
	}

This function in the bridge is unaware of the new field, and so it only populates Outputs.

https://github.com/pulumi/pulumi-terraform-bridge/blob/36b10921bfd25a5cabf0a342d0e449278a256a8b/pkg/tfgen/generate_schema.go#L607-L638