Expose calculations in JS API

[jerivas]

sass/sass#3622
sass/sass-spec#1918
sass/embedded-host-node#237

[jerivas]

@nex3 I'm getting a bunch of call stack errors, it sounds like I'm somehow messing up the methods and getters https://github.com/sass/dart-sass/actions/runs/5205889223/jobs/9391830839?pr=1988

[nex3]

@nex3 I'm getting a bunch of call stack errors, it sounds like I'm somehow messing up the methods and getters https://github.com/sass/dart-sass/actions/runs/5205889223/jobs/9391830839?pr=1988

It's very frustrating that this doesn't actually include the stack trace! My suggestion would be to create a little test.js file that loads the compiled JS from build/npm and directly invokes the functions that are overflowing, and see if that gives more clarity on what the actual recursive call stack is.

[jerivas]

@nex3 I'm working on the changes to Options.functions, and from my understanding we need to simplify return values as explained here:

Return a copy of result.internal with all calculations it transitively contains (including the return value itself if it's a calculation) replaced with the result of simplifying those calculations.

It sounds like we need to modify _parseFunctions to simplify the result if it's a SassCalculation instance, something like this:

if (result is Value) {
  if (result is SassCalculation)
    return SassCalculation._simplify(result);
  return result;
}

But _simplify is a private static method. Should we make it public? Am I approaching this correctly?

[nex3]

@jerivas Since we don't want _simplify to be used by users outside the Sass package (since they can never get ahold of an unsimplified calculation anyway), it may be simpler to just call SassCalculation.calc() instead, which will in practice simplify a calculation.