helm diff fails on NOTES.txt due to unguarded lookup function

[hanxer]

The devtron-operator chart's NOTES.txt template uses Helm's lookup function without nil checking, causing helm diff to fail with a type error.

Error:
Error: Failed to render chart: exit status 1: Error: template: devtron-operator/templates/NOTES.txt:3:58: executing "devtron-operator/templates/NOTES.txt" at <$liveCm.data>: wrong type for
value; expected map[string]interface {}; got interface {}

Environment:

• Chart version: 0.23.0
• Helm version: 3.x
• helm-diff plugin version: latest
• Kubernetes: 1.32

Steps to Reproduce:

1. Install devtron-operator chart
2. Run helm diff upgrade devtron devtron/devtron-operator -n devtroncd

Root Cause:

Helm's lookup function returns nil during helm diff / helm template operations because these commands don't query the Kubernetes API server by design. When NOTES.txt accesses $liveCm.data
without checking if $liveCm is nil, the template fails.

Reference: databus23/helm-diff#263

Suggested Fix:

Add nil guards in templates/NOTES.txt:

{{- $liveCm := lookup "v1" "ConfigMap" .Release.Namespace "configmap-name" }}
{{- if $liveCm }}
{{- if $liveCm.data }}
{{/* safe to access $liveCm.data here */}}
{{- end }}
{{- end }}

Impact:

Users cannot use helm diff or helmfile apply (which uses helm-diff) with this chart.