Unexpected behavior for mutually exclusive fields in a Resource

[birksl]

What version of holos are you using (holos --version)?

0.104.3

Does this issue reproduce with the latest release?

Yes

What did you do?

Created a kubernetes resource definition that includes a mutually exclusive field, registered it in resources.cue and used it as a kubernetes resource in a component.

Steps to reproduce:
In the repro repo, run

$ holos render platform

What did you expect to see?

That holos render platform should succeed.

What did you see instead?

holos render platform fails with the following message:

error at internal/component/component.go:132: holos.spec.artifacts.0.generators.0.resources.Test.test.spec: incomplete value {exclusiveA:"",optionalA?:string,optionalB?:string} | {exclusiveA:"",optionalA?:string,optionalB?:string,exclusiveB:string}
holos.spec.artifacts.0.generators.0.resources.Test.test.spec: incomplete value {exclusiveA:"",optionalA?:string,optionalB?:string} | {exclusiveA:"",optionalA?:string,optionalB?:string,exclusiveB:string}
error at cli/render/render.go:89: could not render component: could not run command:
        /Users/birklewin/go/bin/holos '--log-level' 'info' '--log-format' 'console' 'render' 'component' '--write-to' 'deploy' '--inject' 'holos_component_name=test' '--inject' 'holos_component_path=components/test' './components/test'
        exit status 1

[birksl]

Did a little dive into the code where holos loads the cue module and learned that the instance that is built at internal/component/component.go:119 is essentially the same as running cue eval ./components/test. The output from of these operations looks like this:

$ holos cue eval ./components/test -e Component

Name: "no-name"
Labels: {}
Annotations: {}
Path: "no-path"
Parameters: {}
KustomizeConfig: {
    CommonLabels: {}
    Files: {}
    Kustomization: {
        apiVersion: "kustomize.config.k8s.io/v1beta1"
        kind:       "Kustomization"
    }
    Resources: {}
}
OutputBaseDir: ""
Resources: {
    Test: {
        test: {
            kind: "Test"
            metadata: {
                name:      "test"
                namespace: "test"
            }
            spec: {
                exclusiveA: ""
            }
        }
    }
}
Validators: {}
Artifacts: {
    HolosComponent: {
        artifact: "components/no-name/no-name.gen.yaml"
        generators: [{
            kind:   "Resources"
            output: "resources.gen.yaml"
            resources: {
                Test: {
                    test: {
                        kind: "Test"
                        metadata: {
                            name:      "test"
                            namespace: "test"
                        }
                        spec: {
                            exclusiveA: ""
                        } | {
                            exclusiveA: ""
                            exclusiveB: string
                        }
                    }
                }
            }
        }]
        transformers: [{
            kind: "Kustomize"
            inputs: ["resources.gen.yaml"]
            output: "components/no-name/no-name.gen.yaml"
            kustomize: {
                kustomization: {
                    apiVersion: "kustomize.config.k8s.io/v1beta1"
                    kind:       "Kustomization"
                    resources: ["resources.gen.yaml"]
                }
            }
        }]
        validators: []
    }
}
BuildPlan: {
    kind:       "BuildPlan"
    apiVersion: "v1alpha5"
    metadata: {
        name: "no-name"
    }
    spec: {
        artifacts: [{
            artifact: "components/no-name/no-name.gen.yaml"
            generators: [{
                kind:   "Resources"
                output: "resources.gen.yaml"
                resources: {
                    Test: {
                        test: {
                            kind: "Test"
                            metadata: {
                                name:      "test"
                                namespace: "test"
                            }
                            spec: {
                                exclusiveA: ""
                            } | {
                                exclusiveA: ""
                                exclusiveB: string
                            }
                        }
                    }
                }
            }]
            transformers: [{
                kind: "Kustomize"
                inputs: ["resources.gen.yaml"]
                output: "components/no-name/no-name.gen.yaml"
                kustomize: {
                    kustomization: {
                        apiVersion: "kustomize.config.k8s.io/v1beta1"
                        kind:       "Kustomization"
                        resources: ["resources.gen.yaml"]
                    }
                }
            }]
            validators: []
        }]
    }
}

For some reason cue unifies the spec in the component with both disjunctions in the definition which makes the spec in the artifact an undecided disjunction. The same occurs when specifying only an optional field in the spec in the component, but in that case it is expected, as that is how an option field should be unified with a disjunction of exclusive fields.

-- components/test/component.cue --
package holos

holos: Component.BuildPlan
Component: #Kubernetes & {Resources: Test: test: #Test & {
        metadata: namespace: "test"
        spec: optionalA:     ""
}}
# 
exec holos cue eval ./components/test -e Component.BuildPlan.spec.artifacts
[stdout]
[{
    artifact: "components/no-name/no-name.gen.yaml"
    generators: [{
        kind:   "Resources"
        output: "resources.gen.yaml"
        resources: {
            Test: {
                test: {
                    kind: "Test"
                    metadata: {
                        name:      "test"
                        namespace: "test"
                    }
                    spec: {
                        exclusiveA: string
                        optionalA:  ""
                    } | {
                        exclusiveB: string
                        optionalA:  ""
                    }
                }
            }
        }
    }]
    transformers: [{
        kind: "Kustomize"
        inputs: ["resources.gen.yaml"]
        output: "components/no-name/no-name.gen.yaml"
        kustomize: {
            kustomization: {
                apiVersion: "kustomize.config.k8s.io/v1beta1"
                kind:       "Kustomization"
                resources: ["resources.gen.yaml"]
            }
        }
    }]
    validators: []
}]

For the last case of specifying both exclusive fields, the behavior is also as expected, refusing to unify at all:

-- components/test/component.cue --
package holos

holos: Component.BuildPlan
Component: #Kubernetes & {Resources: Test: test: #Test & {
	metadata: namespace: "test"
	spec: exclusiveA:    ""
	spec: exclusiveB:    ""
}}
# Run
exec holos cue eval ./components/test -e Component.BuildPlan.spec.artifacts
[stderr]
Component.Resources.Test.test.spec: 2 errors in empty disjunction: (and 2 more errors)
Component.Resources.Test.test.spec: 2 errors in empty disjunction:
Component.Resources.Test.test.spec.exclusiveA: field not allowed:
    /Users/birklewin/work/projects/holos-repro-mutual-exclusive/components/test/component.cue:6:8
Component.Resources.Test.test.spec.exclusiveB: field not allowed:
    /Users/birklewin/work/projects/holos-repro-mutual-exclusive/components/test/component.cue:7:8