[app] add validatation for configMaps item has .data

dysnix/app/Chart.yaml

@@ -1,7 +1,7 @@
 apiVersion: v2
 name: app
 description: Generic application Helm chart
-version: 0.3.2
+version: 0.3.3
 engine: gotpl
 sources:
   - https://github.com/dysnix/charts

dysnix/app/templates/_validations.tpl

@@ -6,6 +6,7 @@ Compile all warnings into a single message, and call fail.
 {{- $messages := append $messages (include "app.validateValues.nameGiven" .) -}}
 {{- $messages := append $messages (include "app.validateValues.imageRepositoryGiven" .) -}}
 {{- $messages := append $messages (include "app.validateValues.noSecretsData" .) -}}
+{{- $messages := append $messages (include "app.validateValues.noConfigMapsData" .) -}}
 {{- $messages := append $messages (include "app.validateValues.ingressHasPortsProvided" .) -}}
 {{- $messages := without $messages "" -}}
 {{- $message := join "\n" $messages -}}
@@ -53,6 +54,17 @@ app: no-secrets-data-or-stringdata
 {{- end -}}
 {{- end -}}
 
+{{/* Validate that configMaps have data given */}}
+{{- define "app.validateValues.noConfigMapsData" -}}
+{{- range $_, $values := .Values.configMaps -}}
+{{- if not $values.data -}}
+app: no-configmaps-data
+    Each item of .configMaps must have data field. Please
+    check the input configuration.
+{{- end -}}
+{{- end -}}
+{{- end -}}
+
 {{/* Validate that the enabled ingress has service ports provided */}}
 {{- define "app.validateValues.ingressHasPortsProvided" -}}
 {{- if and .Values.ingress.enabled (not (or .Values.service.port .Values.service.ports)) -}}