How might one apply a type to the root object and a property?

[drewwyatt]

After completing the tutorial, I took a stab at creating types for a Prettier configuration file.

This is what I've got so far.

What i've run into is that, Prettier allows you to define a base config (what I've got in ☝️ that gist), and overrides. Each override can accept all the same options as the base config (minus additional overrides). How could I structure something like that? I could create an Options type, but then I'm not sure how to apply it to the root.

[bioball]

I'd probably do something like this:

open module io.prettier.Options

/// Print semicolons at the ends of statements.
///
/// Valid options:
/// true - Add a semicolon at the end of every statement.
/// false - Only add semicolons at the beginning of lines that may introduce ASI failures.
semi: Boolean?

/// "all" - Trailing commas wherever possible (including function parameters and calls). To run, JavaScript code formatted this way needs an engine that supports ES2017 (Node.js 8+ or a modern browser) or downlevel compilation. This also enables trailing commas in type parameters in TypeScript (supported since TypeScript 2.7 released in January 2018).
/// "es5" - Trailing commas where valid in ES5 (objects, arrays, etc.). Trailing commas in type parameters in TypeScript and Flow.
/// "none" - No trailing commas.
trailingComma: Boolean?

// etc

module io.prettier.PrettierRC

extends "Options.pkl"

/// Overrides let you have different configuration for certain file extensions, folders and specific files.
overrides: Listing<Override>?

class Override {
  files: *Listing<String>|String

  excludeFiles: (*Listing<String>|String)?

  options: Options
}

Basically, you define two separate modules, and the root PrettierRC extends the base options, and then provides overrides as an additional property.

Also: it's better to make these types nullable, because that's how they're represented in Prettier's actual format. Rather than setting defaults explicitly, it's better to leave a doc comment about what Prettier uses if the value is null.

Also: the asterisk on *Listing<String>|String tells Pkl that Listing<String> is the default type. It allows for snippets like this:

files { "*.js" }

Instead of:

files = new Listing { "*.js" }

[bioball]

Also, you might want to add this to your module, because Prettierrc produces JSON. This means that you don't need to provide -f json when rendering using the CLI.

 module io.prettier.PrettierRC

 extends "Options.pkl"

+ output {
+   renderer = new JsonRenderer {}
+ }

[drewwyatt]

No idea how i missed this reply. Thank you for getting back to me so quickly! This makes total sense ❤️