Ability to Dynamically Build Match Cases

[rjray]

Is your feature request related to a problem? Please describe.

I have a case where I want to be able to match against an arbitrary set of value-cases, with the return value of each match being known. The value-cases and matching closures would be derived from input data. For example:

// type AuthorFetchOpts = { aliases: boolean; references: boolean; };

function getScopes(params: AuthorFetchOpts): string {
  return match([params.aliases, params.references])
    .returnType<string[]>()
    .with([false, false], () => ["defaultScope"])
    .with([false, true], () => ["defaultScope", "references"])
    .with([true, false], () => ["defaultScope", "aliases"])
    .with([true, true], () => ["defaultScope", "aliases", "references"])
    .run();
}

(This is a weak example, since in this case I could accomplish this by using filter over the keys of the input object.)

In this example I would prefer to pass in to getScopes a generic Record<string, boolean>, derive the 2^n cases and their return values, and then use match() to process it all. This is similar in nature to the request in #217, I think, but sufficiently different to file this as a new request.

Describe the solution you'd like

Something that creates an initial (or "empty") matcher, allows the programmatic addition of with cases, then can have run called on it.

Describe alternatives you've considered

I have looked at passing multiple patterns to with, but it isn't clear how I would carry over the matching pattern to the handler.