Helm template converting to json

Question

I would like to be able from Helm template file as below to insert template with toJson helm function as explained in the documentation :

value: {{ include "mytpl" . | lower | quote }}

https://helm.sh/docs/howto/charts_tips_and_tricks/#know-your-template-functions

My configuration : _helper.tpl

{{- define "my_tpl" -}}
key1: value1
key2: value2
{{- end -}}

dep.yaml

  template:
    metadata:
      annotations:
        test: >-
          {{ include "my_tpl" . | toJson }}

This should return

  template:
    metadata:
      annotations:
        test: >-
          {"key1":"value1","key2":"value2"}

but it return

  template:
    metadata:
      annotations:
        test: >-
          "key1:value1\nkey2:value2"

I'm using Helm v3. Anyone have an idea please ?

Answer 1

A defined template always produces a string; the Helm-specific include function always returns a string.

In your example, you have a string that happens to be valid YAML. Helm has an undocumented fromYaml function that converts the string to object form, and then you can serialize that again with toJson.

{{ include "my_tpl" . | fromYaml | toJson }}

You may find it easier to have the template itself produce the correct JSON serialization. That could look something like

{{- define "my_tpl" -}}
{{- $dict := dict "key1" "value1" "key2" "value2" -}}
{{- toJson $dict -}}
{{- end -}}

{{ include "my_tpl" . }}

where the "key1", "value1", etc. can be any valid template expression (you do not need nested {{ ... }}).