Immutable Clean

[crishoj]

The documentation rightfully notes that Clean is a mutable operation:

Use Clean to remove excess properties from a value. This function does not check the value and returns an unknown type. You should Check the result before use. Clean is a mutable operation. To avoid mutation, Clone the value first.

What is the idiomatic way to clean values in a non-destructive way?

Would it be Value.Clean(structuredClone(...)), or is there a better option?

[sinclairzx81]

@crishoj Hi,

You can use either structuredClone(...) or Value.Clone(...) prior to calling Value.Clean(T, ...). There isn't really an established idiom for this (just Clone the value before calling mutable Value functions). However, if you're interested, TypeBox internally handles value pipeline operations in the following way (for it's Parse function)

https://github.com/sinclairzx81/typebox/blob/master/src/value/parse/parse.ts#L43-L57

const ParseReducer: ReducerFunction[] = [
  (_schema, _references, value) => Clone(value),
  (schema, references, value) => Default(schema, references, value),
  (schema, references, value) => Clean(schema, references, value),
  (schema, references, value) => Convert(schema, references, value),
  (schema, references, value) => { Assert(schema, references, value); return value },
  (schema, references, value) => (HasTransform(schema, references) ? TransformDecode(schema, references, value) : value),
]
// ------------------------------------------------------------------
// ParseValue
// ------------------------------------------------------------------
function ParseValue<T extends TSchema, R = StaticDecode<T>>(schema: T, references: TSchema[], value: unknown): R {
  return ParseReducer.reduce((value, reducer) => reducer(schema, references, value), value) as R
}

You can use this as a basis for custom value processing.

Hope this helps!
S