TokenSymbol length check mismatch

[dkuehr]

In JavaScript the string length property returns the size in number of characters, however String.length in OCaml returns the size in bytes.

Length check in SnarkyJS:

class TokenSymbol extends Struct(TokenSymbolPure) {
  static get empty() {
    return { symbol: '', field: Field(0) };
  }

  static from(symbol: string): TokenSymbol {
    if (symbol.length > 6)
      throw Error('Token symbol length should be a maximum of 6');
    let field = prefixToField(symbol);
    return { symbol, field };
  }
}

Length check in OCaml:

module Token_symbol = struct
  [%%versioned_binable
  module Stable = struct
    module V1 = struct
      module T = struct
        type t = string [@@deriving sexp, equal, compare, hash, yojson]

        let to_latest = Fn.id

        let max_length = 6

        let check (x : t) = assert (String.length x <= max_length)

This can end in an inconsistent size check if non-ASCII characters are used, for example:
node:

> a = '₿₿₿₿₿₿';
'₿₿₿₿₿₿'
> a.length
6
> (new TextEncoder().encode(a)).length
18

utop:

# String.length "₿₿₿₿₿₿";;
- : int = 18

[mitschabaude]

good catch, thanks! @Trivo25 small guardian task?