Document how to use numbers and booleans in post build substitutions

[stefanprodan]

When using post build substitutions with vars that are numbers or booleans, the reconciliation may fail if the substitution
is for a field that must be of type string. This PR adds a section to the API docs on how to use double quotes vars, and adds unit tests for this procedure.

Fix: fluxcd/flux2#4154
Fix: fluxcd/flux2#1839
Fix: #1096
Fix: #728
Fix: #554

[ahothan]

Stefan, we use quoted int and bool and it works fine with latest flux version (ie it renders as a double quoted string containing the numeric or bool value)

enabled: "'true'"
count: "'40'"

[stefanprodan]

The problem with this "' is that when the var comes as a string it will be invalid, for example some AWS IDs can be int or string.

[ahothan]

not really a problem because for string, the variable value should just be defined in ConfigMap as usual without need for any quoting (or with the regular quoting)

[stefanprodan]

@ahothan your solution doesn't work, using "'${number}'" for metadata labels results in: Invalid value: \"'123'\": a valid label must be a string that consist of alphanumeric characters, '-', '_' or '.'. I think it works for you, because you only do substitutions for Helm values.

[ahothan]

we would not be using "'${number}'" at all

example of definitions in configmap that should all result in a string being rendered

number: "'100'"
condition: "'true'"
text: "anytext_that_is_not_int_or_bool"

and the reference from any flux yaml file (can be in values of HelmRelease or in any part of k8s manifest):

text1: ${text}
text2: ${number:='100'}
text3: ${cond}

rendered:

text1: anytext_that_is_not_int_or_bool
text2: "100"
text3: "true"

I have not tried it on a metadata label but it should work

[ruiengana]

I think this works better...

var="100"
value: ${v="${var}"}

renders

value: "100"

better than having ${quote}${var}${quote} I guess...

[nick4fake]

So... there is still no clean solution? This doesn't work for many cases, like substitutions from configmaps

[stefanprodan]

@nick4fake I don't see why substitutions from ConfigMaps would not work with the solution present in the docs. You can configure it like this:

spec:
  postBuild:
    substitute:
      quote: '"'
    substituteFrom:
      - kind: ConfigMap
        name: cluster-vars