Unable to use stack transformation from unit test

[clstokes]

If I call pulumi.runtime.registerStackTransformation from my Pulumi application and run a unit test against my application, the tests fail to run with the error The root stack resource was referenced before it was initialized. The same Pulumi application runs successfully without error with pulumi preview.

Steps to reproduce

1. git clone https://gist.github.com/20db9640bc9f3c8607f6d67d8390fb45 gh-test && cd gh-test
2. npm i
3. pulumi stack init gh-test
4. npm test
   • Observe error.
5. pulumi preview
   • Observe successful preview.

[lukehoban]

This happens because we do not currently create a root Stack resource automatically in test mode. It is likely that we should, and that setMocks should initialize a root Stack automatically . Coincidentally, we are looking at making that change for Python for other reasons in #4670, but it is likely we should make that same change in Node.js which we fix this issue.

In the meantime, a workaround is to use pulumi.runtime.runInPulumiStack to construct a Stack resource.

pulumi.runtime.setMocks({
    call: x => {
        return {};
    },
    newResource: x => {
        return {id: "", state: {}};
    }
})
pulumi.runtime.runInPulumiStack(async () => {
    pulumi.runtime.registerStackTransformation(args => {
        console.log(`transofming: ${args.name}`)
        return {
            opts: args.opts,
            props: args.props,
        }
    })
    
    // Create an AWS resource (S3 Bucket)
    const bucket = new aws.s3.Bucket("my-bucket");
    
    // Export the name of the bucket
    return {
        bucketName: bucket.id
    };
})

[amichel]

This problem scope is bigger than just unit tests. I have common transformations that I want to be able to reuse in all projects as npm package. It also causes problem the other way around, when I register stack transformation, it doesn't apply on resources created by modules from shared npm packages.

[clstokes]

Related - #6214

[arwilczek90]

I agree with @amichel I get the same traceback when running pulumi up on a project with a stack transformation.