Conditional expressions in helm

2 min read | by Jordi Prats

Maybe one of the main challenges about helm is the complexity of it's template rendering engine: It's not very intuitive

• If we want to use an if/else construct it works as we are used to:

{{ if .Values.debug }}
  # Do something
{{ else }}
  # Do something else
{{ end }}

• We can have elseif nesting expressions:

{{ if .Values.debug.info }}
  # Do something
{{ else if .Values.debug.err }}
  # Do something else
{{ else }}
  # Default
{{ end }}

When working with more complex expressions is when we will start to feel the pain. Since they have been implemented as functions, the resulting expression looks like follows:

• And and expression will look like this:

{{ if and .Values.aws.lambda .Values.aws.ecs }}

• Same applies for a or expression:

{{ if or .Values.aws.lambda .Values.aws.ecs }}

• We can test for equality using the eq operator with the same exact syntax:

{{ if eq .Values.aws.defaultAccount "blue" }}

• And inequality:

{{ if ne .Values.aws.defaultAccount "blue" }}

• Along with other string functions, we can check if some string is contained on some other with the contains function:

{{ if contains .Values.aws.environment "test" }}

• To negate an expression it's more intuitive:

{{ if not .Values.aws.lambda.enabled }}

If you need to negate the result of a comparison you can nest both expressions:

{{ if not (contains .Values.aws.environment "test") }}

Posted on 14/07/2021