Wordlist typing improvement

[jurajpiar]

Describe the Feature

Currently, the wordlists const's type is { [ locale: string ]: Wordlist }, which does not restrict from using different locale strings, which would then undefined in runtime. Instead, I suggest to make the wordlists the signle source of truth ie use const assertion, and draw the type from it. This way the consuming code will complain in compile-time if given locale does not exist.
Extensibility would not be hindered as one can always do something like:

const customWordlists = {
    ...wordlists,
    en: customEnWordlist,
    jp: jpWordlist
} as const;

type CustomLocale = keyof typeof customWordlists;

I've made a PR to reflect this.

Code Example

import {Locale, wordlists} from '@ethersproject/wordlists';


type Configuration = {
  mnemonicLanguage: Locale
};

const bad_config: Configuration = {
  mnemonicLanguage = 'Klingon' // type error 
}

const config: Configuration = {
  mnemonicLanguage = 'en' // :) happy as exists in Locale
}

const wordlist = wordlists[config.mnemonicLanguage];

[ricmoo]

Moving this to the Ideas Discussion.

In general, it is hard to find an elegant way to add all the wordlists, because English makes up about 100% - epsilon of the use-cases, but I definitely want to support broader and more inclusive support.

But, each word list adds to the size and is rarely used. In v6, I've managed to get the size down to 54kb for the other 9 languages, but they are stripped out by default for the web /dist build (with a dist/ file to import them additionally). In which case even allowing auto-complete could fail post-bundle.

Le sigh...