Consider using Intl.PluralRules instead of make-plurals

[timofei-iatsenko]

This has decent browser support, including Node.js:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/PluralRules/PluralRules

https://caniuse.com/intl-pluralrules

So instead of:

import { i18n } from '@lingui/core';
import { en, cs } from 'make-plural/plurals'

i18n.loadLocaleData({
  en: { plurals: en },
  cs: { plurals: cs },
})

export async function dynamicActivate(locale: string) {
  const { messages } = await import(`./locales/${locale}/messages`)
  i18n.load(locale, messages)
  i18n.activate(locale)
}

We can do:

import { i18n } from '@lingui/core';

export async function dynamicActivate(locale: string) {
  const {messages} = await import(`./locales/${locale}/messages`)
  const pluralRules = new Intl.PluralRules(locale)

  i18n.loadLocaleData({
    [locale]: {plurals: (number) => pluralRules.select(number)}
  })
  i18n.load(locale, messages)
  i18n.activate(locale)
}

Things to consider:

1. Can we make this as a default behavior with optional fallback to 'make-plural/plurals' or polyfill for older runtimes?
2. Does Intl.PluralRules supported in ReactNative (in both platforms?) https://formatjs.io/docs/guides/runtime-requirements#react-native
3. Nothing preventing us from updating docs right now with examples of usage Intl.PluralRules instead of make-plural/plurals

Links:

• https://unicode-org.github.io/cldr-staging/charts/37/supplemental/language_plural_rules.html#rules
• https://formatjs.io/docs/polyfills/intl-pluralrules/
• feat: add plural rule into compiled catalogs #1311

[Martin005]

For our current implementation, it would not be as easy as only instantiating new Intl.PluralRules object. We would need two because when you make a new Intl.PluralRules, you need to specify if you want either cardinal (default) or ordinal plural rules, you can't get both from one object.

[timofei-iatsenko]

Yes, i know. I'm going to make it a default behavior so users won't need to i18n.loadLocaleData at all. All this setup would happen inside of a lib. We use Intl objects anyway, so it will not add additional requirements for runtime.