Accessing amended values without declaring locals

[rohan-datar]

I'm trying to create a template with certain constant values that'd I'd like to be accessible to users of the template. Is there a way to do this without creating a local in the amended module?

Here's a very minimal example of what I'm talking about

// template.pkl

module template

const value = "some constant value"

config: Listing<String>

// config.pkl

amends "template.pkl"

config = new Listing {
    "foo"
    "bar"
    "baz-\(value)"
}

Trying to evaluate this returns an error: Cannot find property `value`.

I can sort of overcome this by defining a local property:

// config2.pkl

amends "template.pkl"

local val = value

config = new Listing {
    "foo"
    "bar"
    "baz-\(val)"
}

However, in more complex scenarios this becomes very inconvenient. When you have several levels of amended templates for instance. Needing to create a local property in every place in the template hierarchy where you need to use the value quickly becomes a problem. Is there a better way to accomplish this?

[bioball]

You can access this using module:

config {
    "foo"
    "bar"
    "baz-\(module.value)"
}

[rohan-datar]

Thanks! That works great. I had no idea module was a keyword.

As a follow up, is there a way to do something similar for amended objects?

[bioball]

Can you elaborate on that? Do you have an example?

[rohan-datar]

I realized that the amending syntax for objects forces you to give them an identifier in scope, so this isn't an issue.

i.e in

tortoise = (dodo) { 
  name = "Galápagos tortoise"
  taxonomy { 
    `class` = "Reptilia" 
  }
}

dodo is accesssible inside the definition of tortoise

[bioball]

Gotcha.

Also, there is super, which is useful in cases where you have an amends declaration. For example:

tortoise {
  name = "\(super.name) tortoise"
  taxonomy { 
    `class` = "Reptilia" 
  }
}

Note that tortoise { ... } is practically the same as tortoise = (super.tortoise) { ... }.

[StefMa]

I found this and I have the feeling my case / question is similar but I don't get it to work.
My template:

something .. something

local baseHeaderComment = "# Do not modify!\n# This file was generated from a template using https://github.com/StefMa/pkl-gha"
headerComment: String? = null
local finalHeaderComment: String = if (headerComment != null) "\(headerComment)\n\n" + baseHeaderComment else baseHeaderComment
output {
  text = "\(finalHeaderComment)\n\n\(super.text)"
  renderer = new YamlRenderer {
    converters {
      ["headerComment"] = (headerComment: String?) -> null
    }
  }
}

My consumer can (don`t have to) override it like this:

amends "../GitHubAction.pkl"

headerComment = """
  # SPDX-FileCopyrightText: Copyright line here
  #
  # SPDX-License-Identifier: License here
  """

However, I don't like that I have the headerComment as a "templating value".
Actually it isn't something for the (in this case) GitHub Action yml directly.
I would be more happy if I could to like module.headerComment = "" or super.headerComment = "".
Just to scope it a bit away from the "real github action templating".
But it seems that is not possible?

I also thought introducing a class like pklGhaSettings { headerComment = "" }?! 🤔

An advice how to model this would be great.
Maybe having this as a templating property isn't that worth as I think it is?! 🤔