Add Dynamic.toMixin() method

[Mikulas]

Adds a toMixin() method to the Dynamic class that converts a Dynamic object into a Mixin function applicable via the pipe operator (|>).

A generic toMixin() method cannot be implemented in user land, so this implementation provides a native method that properly handles:

• Property merging and overriding
• Element appending with correct index offsetting
• Entry merging with proper key handling
• Nested object replacement vs amendment semantics

Implementation uses the source Dynamic's enclosing frame to ensure proper module context for type resolution during member evaluation.

[HT154]

Can this not be done in userland Pkl?

function dynamicToMixin(mix: Dynamic): Mixin = new {
  ...mix
}

It's likely that the "deep" variant of this that recursively turns a nested object structure (and not just a Dynamic!) into a Mixin isn't userland-friendly, but I'm not sure there needs to be an API for the shallow implementation.

Missed the implementation detail that makes this work, never mind :)

[HT154]

This is not a sound assumption to make. Mappings and Dynamics can have entries with Int (in Pkl, Long in Java) keys. Probably better to check member.isElement() here instead (and you can then assume the key is a Long).

[Mikulas]

This would be the internal field representation, not the userland defined keys. I will see if I can get the key to be the right type at compile time and replace this check

[Mikulas]

@HT154 I don't believe so due to how amends vs replacements are constructed. Consider this example:

local base = new {
  a1 {
    b1 = 2
  }
  a2 {
    b1 = 2
  }
}

local over = new Mixin {
  a1 = new Dynamic {
    b2 = 2
  }
  a2 {
    b2 = 2
  }
}

local overrideValue = new Dynamic {} |> over

function dynamicToMixin(mix: Dynamic): Mixin = new {
  ...mix
}

actualValue = base |> dynamicToMixin(overrideValue)

expectedValue = base |> over

Which evaluates to

actualValue {
  a1 {
    b2 = 2
  }
  a2 { // ❗️This is not correct, the original Mixin has amend semantics here, not replace
    b2 = 2
  }
}
expectedValue {
  a1 {
    b2 = 2
  }
  a2 {
    b1 = 2
    b2 = 2
  }
}