Helm optional nested variables

Question

How do I make an optional block in the values file and then refer to it in the template?

For examples, say I have a values file that looks like the following:

# values.yaml foo:    bar: "something" 

And then I have a helm template that looks like this:

{{ .Values.foo.bar }} 

What if I want to make the foo.bar in the values file optional? An error is raised if the foo key does not exist in the values.

I've tried adding as an if conditional. However, this still fails if the foo key is missing:

{{ if .Values.foo.bar }} {{ .Values.foo.bar }} {{ end }} 

Any thoughts are much appreciated.

Answer 1

Simple workaround

Wrap each nullable level with parentheses ().

{{ ((.Values.foo).bar) }} 

Or

{{ if ((.Values.foo).bar) }} {{ .Values.foo.bar }} {{ end }} 

How does it work?

Helm uses the go text/template and inherits the behaviours from there.

Each pair of parentheses () can be considered a pipeline.

From the doc (https://pkg.go.dev/text/template#hdr-Actions)

It is:

The default textual representation (the same as would be printed by fmt.Print)...

With the behaviour:

If the value of the pipeline is empty, no output is generated... The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero.

As such, by wrapping each nullable level with parentheses, when they are chained, the predecessor nil pointer gracefully generates no output to the successor and so on, achieving the nested nullable fields workaround.