Deep merge of values files

[thomastaylor312]

Helm should be able to deep merge multiple values files. This is helpful when you want to pass different variables for different environments (like whether or not to use a PVC) As it stands right now, it just overwrites the previous variable.

Example

Given these two values files for an example postgresql subchart

secrets.yaml

postgresql:
  postgresPassword: "super-secret-pass"

dev_environment.yaml

postgresql:
  persistence:
    enabled: false

Current Behavior
When using -f secrets.yaml -f dev_environment.yaml with helm install, the variables available would look like this:

postgresql:
  persistence:
    enabled: false

If we swap the flags: -f dev_environment.yaml -f secrets.yaml, the variables look like:

postgresql:
  postgresPassword: "super-secret-pass"

Desired Behavior
When using -f secrets.yaml -f dev_environment.yaml with helm install, the variables available would look like this:

postgresql:
  postgresPassword: "super-secret-pass"
  persistence:
    enabled: false

Is there another way to get this behavior or would this need to be added?

[thomastaylor312]

Side note: I know that this would make the ordering of the files passed with the -f flag important, because if there are variables with the same name, one would overwrite the others.

[technosophos]

I am not sure Cobra will allow us to repeat flags. But if we can figure out a way around that, I think we could just pass files through the existing -f/--set merge logic.

We might be able to change -f to accept a []string, which (IIRC) is expressed on CLI as -f foo.yaml,bar.yaml.

[thomastaylor312]

@technosophos: Thanks for the quick response. It looks like it does (from the godoc example):

// Set is the method to set the flag value, part of the flag.Value interface.
// Set's argument is a string to be parsed to set the flag.
// It's a comma-separated list, so we split it.
func (i *interval) Set(value string) error {
    // If we wanted to allow the flag to be set multiple times,
    // accumulating values, we would delete this if statement.
    // That would permit usages such as
    //	-deltaT 10s -deltaT 15s
    // and other combinations.
    if len(*i) > 0 {
        return errors.New("interval flag already set")
    }
    for _, dt := range strings.Split(value, ",") {
        duration, err := time.ParseDuration(dt)
        if err != nil {
            return err
        }
        *i = append(*i, duration)
    }
    return nil
}