Filtering Empty Objects in SDK to Avoid Invalid Resource Generation/Apply

[haarchri]

What happened?

When using for example function-kcl to create resources, the following pattern can lead to the generation of invalid resources that result in client-side crossplane beta render or server-side errors during the application:

 _items = [{
    apiVersion: "s3.aws.upbound.io/v1beta1"
    kind: "Bucket"
    metadata: _metadata("bucket")
    spec: _defaults
}]

_items += [{
    apiVersion: "s3.aws.upbound.io/v1beta1"
    kind: "BucketVersioning"
    metadata: _metadata("bucketVersioning")
    spec: _defaults | {
        forProvider: {
            bucketSelector: {
                matchControllerRef: True
            },
            versioningConfiguration: [
                {
                    status: "Enabled"
                },
            ],
        },
    }
} if get(oxr, "spec.parameters.versioning", "False") else {}]

items = _items 

This approach can produce an invalid resource object like the one shown below if the conditional logic produces an empty object ({}):

---
metadata:
  annotations:
    crossplane.io/composition-resource-name: ""
  generateName: configuration-
  labels:
    crossplane.io/composite: configuration
  ownerReferences:
  - apiVersion: example.org/v1alpha1
    blockOwnerDeletion: true
    controller: true
    kind: Template
    name: configuration
    uid: "" 

The issue arises because the condition for else produces {}, which is added to the _items list. This can lead to errors during the resource application process.

To mitigate this, every individual composition currently requires an additional filtering step:

items = [
    i for r in [_items]
    for i in r if i
]

Can the SDK be enhanced to automatically filter out these invalid empty object resources? This would simplify the composition logic and prevent potential errors during resource application.

This issue has been discussed in the KCL community. You can find the discussion here: https://cloud-native.slack.com/archives/C05TC96NWN8/p1723020486395609

How can we reproduce it?

What environment did it happen in?

Crossplane version: