nil pointer evaluating interface when installing a helm chart - kubernetes

Question

I'm trying to install a chart to my cluster but I'm getting a error
Error: template: go-api/templates/deployment.yaml:18:24: executing "go-api/templates/deployment.yaml"
at <.Values.deployment.container.name>: nil pointer evaluating interface {}.name
However I executed the same commands for another 2 charts and it worked fine.
The template file I'm using is this:
apiVersion: apps/v1
kind: Deployment
metadata:
namespace: {{ .Values.namespace}}
labels: {{- include "chart.labels" . | nindent 4 }}
name: {{ .Values.deployment.name}}
spec:
replicas: {{ .Values.deployment.replicas}}
selector:
matchLabels: {{ include "chart.matchLabels" . | nindent 6 }}
template:
metadata:
labels:
app.kubernetes.io/name: {{ template "chart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
spec:
containers:
- name: {{ .Values.deployment.container.name }}
image: {{ .Values.deployment.container.image }}
imagePullPolicy: Never
ports:
- containerPort: {{ .Values.deployment.container.port }}

Answer 1

This can happen if the Helm values you're using to install don't have that particular block:
namespace: default
deployment:
name: a-name
replicas: 1
# but no container:
To avoid this specific error in the template code, it's useful to pick out the parent dictionary into a variable; then if the parent is totally absent, you can decide what to do about it. This technique is a little more useful if there are optional fields or sensible defaults:
{{- $deployment := .Values.deployment | default dict }}
metadata:
name: {{ $deployment.name | default (include "chart.fullname" .) }}
spec:
{{- if $deployment.replicas }}
replicas: {{ $deployment.replicas }}
{{- end }}
If you really can't work without the value, Helm has an undocumented required function that can print a more specific error message.
{{- $deployment := .Values.deployment | required "deployment configuration is required" }}
(My experience has been that required values are somewhat frustrating as an end user, particularly if you're trying to run someone else's chart, and I would try to avoid this if possible.)
Given what you show, it's also possible you're making the chart too configurable. The container name, for example, is mostly a detail that only appears if you have a multi-container pod (or are using Istio); the container port is a fixed attribute of the image you're running. You can safely fix these values in the Helm template file, and then it's reasonable to provide defaults for things like the replica count or image name (consider setting the repository name, image name, and tag as separate variables).
{{- $deployment := .Values.deployment | default dict }}
{{- $registry := $deployment.registry | default "docker.io" }}
{{- $image := $deployment.image | default "my/image" }}
{{- $tag := $deployment.tag | default "latest" }}
containers:
- name: app # fixed
image: {{ printf "%s/%s:%s" $registry $image $tag }}
{{- with .Values.imagePullPolicy }}
imagePullPolicy: {{ . }}
{{- end }}
ports:
- name: http
containerPort: 3000 # fixed

Answer 2

If the value is defined in your values file, and you're still getting the error then the issue could be due to accessing that value inside range or similar function which changes the context.
For example, to use a named template mySuffix that has been defined with .Values and using that inside range with template function, we need to provide $ to the template function instead of the usual .:
{{- define "mySuffix" -}}
{{- .Values.suffix }}
{{- end }}
...
{{- range .Values.listOfValues }}
echo {{ template "mySuffix" $ }}
{{- end }}