Flask-Babel zh-TW, zh-HK 對應到 zh_Hant ， zh-CN 、 zh-SG 對應到 zh_Hans

Flask-Babel 下， zh-TW, zh-HK 語言對應到 zh_Hant ， zh-CN 、 zh-SG 語言對應到 zh_Hans 的解法。

Fixing request.accept_languages.best_match() to match zh-TW, zh-HK against zh_Hant, and zh-CN, zh-SG to zh_Hans in Flask-Babel.

from babel import Locale
from werkzeug.datastructures import LanguageAccept


@babel.localeselector
def get_locale():
    """Returns the locale of the user

    :return: The locale of the user.
    """
    return __fix_accept_language(request.accept_languages)
        .best_match(current_app.config["ALL_LOCALES"])


def __fix_accept_language(accept: LanguageAccept) -> LanguageAccept:
    """Fixes the accept language so that territory variants may be matched to
    script variants.  For example, zh_TW, zh_HK to zh_Hant, and zh_CN, zh_SG to
    zh_Hans.  This is to solve the issue that Flask only recognizes the script
    variants, like zh_Hant and zh_Hans.

    :param accept: The original HTTP accept languages.
    :return: The fixed HTTP accept languages.
    """
    accept_list: t.List[t.Tuple[str, float]] = list(accept)
    to_add: t.List[t.Tuple[str, float]] = []
    for pair in accept_list:
        locale: Locale = Locale.parse(pair[0].replace("-", "_"))
        if locale.script is not None:
            tag: str = F"{locale.language}-{locale.script}"
            if tag not in accept:
                to_add.append((tag, pair[1]))
    accept_list.extend(to_add)
    return LanguageAccept(accept_list)