ExtraResources.matchName doesn't find my XR but matchLabels does

[mattupstate]

What happened?

With Crossplane 2 I'm trying to get a reference to an existing instance of a custom XR. I'm trying to reference it like so:

apiVersion: meta.gotemplating.fn.crossplane.io/v1alpha1
kind: ExtraResources
requirements:
  serviceStacks:
    apiVersion: stacks.example.acme.com/v1alpha1
    kind: ServiceStack
    matchName: {{ .observed.composite.resource.spec.stackRef.name }}

But the slice, referenced through getExtraResources . "serviceStacks", is always empty. However, if I query labels added by Crossplane the slice is not empty, like so:

apiVersion: meta.gotemplating.fn.crossplane.io/v1alpha1
kind: ExtraResources
requirements:
  serviceStacks:
    apiVersion: stacks.example.acme.com/v1alpha2
    kind: ServiceStack
    matchLabels:
      crossplane.io/composite: {{ .observed.composite.resource.spec.stackRef.name }}

The slice contains one element. However, and this makes no sense to me, I can't get at it through a slice index. I have no issues seeing the reference if I iterate the slice like so:

---
apiVersion: v1
kind: ConfigMap
metadata:
  annotations:
    {{ setResourceNameAnnotation "debug-cm" }}
data:
  {{- $someExtraResources := getExtraResources . "serviceStacks" }}
  {{- range $i, $extraResource := $someExtraResources }}
  item-{{ $i }}: "{{ $extraResource.resource.metadata.name }}"
  {{- end }}

The resulting ConfigMap looks like this:

apiVersion: v1
kind: ConfigMap
data:
  item-0: acme-example-service

But using index like so:

apiVersion: v1
kind: ConfigMap
metadata:
  annotations:
    {{ setResourceNameAnnotation "debug-cm" }}
data:
  {{- $someExtraResources := getExtraResources . "serviceStacks" }}
  {{- $extraResource := (index $someExtraResources 0) }}
  item: "{{ $extraResource.resource.metadata.name }}"

I always get an out of range error:

cannot compose resources: pipeline step "render-templates" returned a fatal result: cannot execute template: template: manifests:50:25: executing "manifests" at <index $someExtraResources 0>: error calling index: reflect: slice index out of range

What on earth am I misunderstanding?

Is this maybe a side effect of the underlying Crossplane SDK in the function pinned to a 1.X version? Perhaps similar to #483?

What environment did it happen in?

Crossplane 2. Latest version of function.

[tiagat-goreel]

I encountered a similar problem when it was impossible to get the slice by index 0
I worked around it as follows:

{{ $myResource := index .context "apiextensions.crossplane.io/extra-resources" "myResource" | first }}