Values merge with nil and map doesn't work

[mattymo]

Problem: Map should always win over nil in a values merge scenario.

Scenario to reproduce

values1.yaml:

components:
  etcd-operator:

values2.yaml:

components:
  etcd-operator:
    version:  0.10.3

helmfile.yaml

repositories:
- name: "stable"
  url: "https://kubernetes-charts.storage.googleapis.com"

environments:
  default:
    values:
      - values1.yaml
      - values2.yaml

releases:
- name: "etcd-operator"
  chart: stable/etcd-operator
{{- if .Values.components | getOrNil "etcd-operator" | getOrNil "version" }}
  version: {{ .Values.components  | getOrNil "etcd-operator"  | getOrNil "version"  }}
{{- end }}

The result is that the second values file doesn't properly merge if the first one contains any nil values. In the resulting values set, .Values.components["etcd-operator"] is nil.

Helmfile version:
helmfile version v0.102.0

[mumoshu]

@mattymo Good catch! Unfortunately, we can't easily avoid this due to the library which Helmfile uses under the hood to merge maps. The issue is darccio/mergo#123, which prevents Helmfile from overwriting nil values with maps.

The workaround would be to modify your values1.yaml to have an empty object where you expect to overwrite later, so that it looks:

components:
  etcd-operator: {}

$ helmfile build
---
#  Source: helmfile.yaml

filepath: helmfile.yaml
environments:
  default:
    values:
    - values1.yaml
    - values2.yaml
repositories:
- name: stable
  url: https://kubernetes-charts.storage.googleapis.com
releases:
- chart: stable/etcd-operator
  version: 0.10.3
  name: etcd-operator
templates: {}

[mattymo]

@mumoshu Thanks for the quick response. I really hope someone fixes it in the library soon. This can't be an impossible task

[mumoshu]

@mattymo I was reading the mergo code and it turned out that bumping mergo fixes this specific issue for me. Could you give it a try with Helmfile v0.104.0 which has just been released?

[mattymo]

@mumoshu I confirmed this bug is fixed. I uncovered yet another (similar) one and I'll open a separate issue.