Best Approach for Generating ReScript Builder Patterns with Custom Attributes

I often build some functions which will traverse my types at runtime and print them to stdout.
So I can run these scripts with node / bun and pipe the output to another file.

Here is a very simple example:

// Type Gen

let makeBuilder = (form) => {
  Console.log("type t = {")

  form->Obj.magic->Dict.forEachWithKey((field, fieldName) => {
    let dt = switch field {
      | JSON.String(_) => "option<string>"
      | JSON.Number(_) => "option<int>"
      // ...
    }

    Console.log(`  ${fieldName}: ${dt},`)
  })

  Console.log("}")
}

type form = {
  name: string,
  age: int,
}

makeBuilder({
  name: "", 
  age: 0,
})

// Result

type t = {
  name: option<string>,
  age: option<int>,
}

If the runtime type is not enough, you could also add some helper functions for the fields:

// Type Gen

let makeBuilder2 = (form) => {
  Console.log("type t = {")

  form->Obj.magic->Dict.forEachWithKey((field, fieldName) => {
    Console.log(`  ${fieldName}: ${field},`)
  })

  Console.log("}")
}

let string: string = Obj.magic("option<string>")
let int: int = Obj.magic("option<int>")
let float: float = Obj.magic("option<float>")

type form2 = {
  someString: string,
  someInt: int,
  someFloat: float,
}

makeBuilder2({
  someString: string, 
  someInt: int,
  someFloat: float,
})

// Result

type t = {
  someString: option<string>,
  someInt: option<int>,
  someFloat: option<float>,
}

Of course, you have to handle nested types, variants, etc, but just the idea.
I know, It’s a bit more boilerplate, but

1. it’s simple rescript code
2. it doesn’t need a complex toolchain, parsers, whatever

If you would run a small script (maybe a filewatcher) on a predefined folder, you could also split these types into different input and output files.

You can find a more complex example of my approach in my sql query builder.