Merging two Dictionaries in Helm - kubernetes-helm

Question

I am using Helm 3. I have two values.yaml files. In common/values.yaml I have defined:
deployment:
ports:
- name: http
protocol: TCP
The common is of the type library. In my-app, which is of the type application, the common is added as a dependency. In my-app/values.yaml I have added:
deployment:
ports:
- containerPort: 8081
I have defined a template _deployment.yaml in common/templates. In this file I am trying to merge these two deployment dictionaries into one by using:
{{- $deployment := merge .Values.common.deployment .Values.deployment -}}
When I am printing {{ $deployment }}, it is giving output:
map[ports:[map[containerPort:8080 name:http protocol:TCP]]]
And if I do:
{{- $deployment := merge .Values.deployment .Values.common.deployment -}}
The output of {{ $deployment }} is:
map[ports:[map[containerPort:8081]]]
Moreover the output of {{ .Values.common.deployment }} is:
map[ports:[map[name:http protocol:TCP]]]
And the output of {{ .Values.deployment }} is:
map[ports:[map[containerPort:8081]]]
What I would like to have after merging is:
deployment:
ports:
- name: http
protocol: TCP
containerPort: 8081
Any advice you could give would be much appreciated.

Answer 1

Looks like the merge operation does not work as expected on lists (it's a common problem, as the merge operation is ambiguous on list: should a list be appended or replaced when merging ?)
Anyway, I would suggest to merge the ports data with:
{{- $ports := merge .Values.deployment.ports[0] .Values.common.deployment.ports[0] -}}
and render the result with:
deployment:
ports:
- {{- toJson $ports }}
HTH