helm: Values file key deletion doesn't work

I tried to use the feature to delete default keys (documented here) but it doesn’t work.

To test it I created a simple values.yaml file like this;

a: a
b: b
c: c

and a small template:

apiVersion: v1
kind: ConfigMap
metadata:
  name: test
data: |
{{- range $key, $value := .Values }}
  {{ $key }} - {{ $value }}
{{- end }}

When I try to delete the “b” key like this helm install test-chart --debug --dry-run --set b=null I get this:

COMPUTED VALUES:
a: 1
b: "null"
c: 3

HOOKS:
MANIFEST:

---
# Source: test-chart/templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test
data: |
  a - 1
  b - null
  c - 3

I also tried grabbing the source code and looking at the values and I think I found what part of the problem is. In the “coalesceValues” method there is a check for value == nil (see here). According to the commit message it’s expecting the value to be nil at this point but what I found out is that the value is actually a string with the value “null”. So instead of deleting the key we actually end up using the key with a value of “null”