Is there a private/public attribute for members?

[gian-didom]

Hello,

I am exploting Pkl to configure a distributed simulation environment with multiple machines. Every machine has its own settings format, and the idea is to use Pkl to centralize the configuration and output properly-formatted files to share with the machines.

Sometimes, I feel the machine-level configuration (to which I have no access) could be written better; for this, in the corresponding .pkl file, I change some property name and type, and map them to the actual configuration format by exploiting hidden attributes.

An example:

class Host {
    hostname : String
    port: Int
    protocol: 'tcp' | 'udp' 
}

hidden host : Host
hostname : String = host.hostname
port : Int = host.port

This allows me to only edit the host properties (getting it, for instance, from an external module) and automatically fill-in the hostname and port as required by the output file.

However, users can theoretically still manually set the hostname and port properties, breaking the link between these properties and the host : Host object. I could throw an error if (module.port != module.host.port) but I find this a bit cumbersome, as I'd need to re-assert every link.

Is there any way to make hostname and port "private", in the sense that they cannot be amended? I looked up at the Language reference, but I couldn't find any feature supporting this.

[HT154]

You're looking for the fixed modifier! See https://pkl-lang.org/main/current/language-reference/index.html#fixed-properties

[gian-didom]

Exactly what I was looking for! Many thanks!