How to call toYaml and exclude particular key?

Question

Inside the template I have a fragment like this:

props: {{- toYaml .Values.myApp.container.props }}

currently props contains 4 children:

...
    container:
      props:
        a: ...
        b: ...
        c: ...
        d: ...

But I want to exclude c on the fly. Is there way to do it ?

score 1 · Accepted Answer · answered Mar 22 '23 at 08:55

1

Try:

{{ $myProps := .Values.myApp.container.props }}
{{ $_ := unset $myProps "c" }}

Then you can use it, for example:

props: {{ $myProps | toYaml | nindent 2 }}

which leads to:

props: 
  a: 1
  b: 2
  d: 4

answered Mar 22 '23 at 08:55

Andromeda

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Sorry, but what is "$_" ? – gstackoverflow Mar 22 '23 at 09:36
This is explained in official docs: `Note that set returns the dictionary (a requirement of Go template functions), so you may need to trap the value as done above with the $_ assignment.` https://helm.sh/docs/chart_template_guide/function_list/#set. It is also true for `unset`. – Andromeda Mar 22 '23 at 09:48
so `$_` is just a variable name ? – gstackoverflow Mar 22 '23 at 13:16
Yes. It is called blank identifier in golang. – Andromeda Mar 22 '23 at 15:05

score 0 · Answer 2 · answered Mar 21 '23 at 16:29

The docs say

This function is equivalent to GoLang yaml.Marshal function, see docs here: https://pkg.go.dev/gopkg.in/yaml.v2#Marshal

That function does support excluding certain fields, however this works by annotating Go types which is not viable here. So you'd need to remove the field before piping the values into toYaml.

Helm does provide a without function, however that only works on lists. So you seem to be out of luck here.

A last resort would be to use regexReplaceAll on the resulting YAML string, but… do you really want to do that?

score 0 · Answer 3 · answered Jul 16 '23 at 19:47

Helm includes a function on dictionaries called omit.

The omit function is similar to pick, except it returns a new dict with all the keys that do not match the given keys. Example:
$myDict := dict "name1" "value1" "name2" "value2" "name3" "value 3"
$new := omit $myDict "name1" "name3"
The above returns {name2: value2}

In your case this would mean:

props: {{ omit .Values.myApp.container.props "c" | toYaml }}

How to call toYaml and exclude particular key?

3 Answers3