Default value in Helm

Question

I have a configmap yaml that needs to be executed if a particular value is set to true. This is the config map yaml def

{{ if (.Values.telemetry.create) }}
apiVersion: v1
kind: ConfigMap
metadata:
  name: telemetry-allowlist
data:
  metrics.json: |
    {
...

Now in some cases users forget to add this value .Values.telemetry.create

This causes the entire setup to fail with the error

at <.Values.telemetry.create>: nil pointer evaluating interface {}.create

Wondering how to add default values so that it defaults to false if the value is not present

Does this answer your question? [Helm chart fails with "nil pointer evaluating interface {}" when trying to evaluate a missing nested key](https://stackoverflow.com/questions/61154736/helm-chart-fails-with-nil-pointer-evaluating-interface-when-trying-to-evalu) — David Maze, Dec 13 '21 at 18:47
You can assign `{{ $telemetry := .Values.telemetry | default dict }}` and then test on `{{ $telemetry.create }}`. That will substitute an empty dictionary for the nil value and avoid the error. — David Maze, Dec 13 '21 at 18:48

score 1 · Answer 1 · answered Dec 14 '21 at 06:09

In order to avoid telemetry being empty, you need to add additional judgments.

According to the helm document, when the object is empty, the if statement judges to return false.

A pipeline is evaluated as false if the value is:

a boolean false
a numeric zero
an empty string
a nil (empty or null)
an empty collection (map, slice, tuple, dict, array)

{{ if .Values.telemetry }}
{{ if .Values.telemetry.create }}
apiVersion: v1
kind: ConfigMap
metadata:
  name: telemetry-allowlist
data:
  metrics.json: |
    {
...

score 0 · Answer 2 · answered Jan 12 '22 at 07:24

You can set telemetry.create to false in your default values.yaml file.

...
telemetry:
  create: false
...

So even if users miss setting the telemetry.create value, the helm will render from the default values.yaml file and you won't get the nil pointer error.

Default value in Helm

2 Answers2