[mono] Browser's ICU limitations

[EgorBo]

We use a stripped version of ICU data file. The default size is ~30Mb (or ~5mb after compression) - we reduced it down to 1.39Mb (or ~302kb compressed) by removing some features we don't need to can give up on. The main filter file is located here: https://github.com/dotnet/icu/blob/maint/maint-67/icu-filters/optimal.json

Here is a list of known limitations:

• CultureInfo.EnglishName returns "locale" as a name, e.g. "en (US)" instead of "English (United States)"
• CultureInfo.NativeName returns "locale" as a name, e.g. "ru (RU)" instead of "русский (Россия)"
• List of supported locales is limited (see list here).
• DateTimeFormatInfo.NativeCalendarName is not supported.
• RegionInfo.NativeName returns a short name e.g. "US" instead of "United States" etc.
• String.Normalize and String.IsNormalized don't support rarely used NormalizationForm.FormKC and NormalizationForm.FormKD forms.
• RegionInfo.CurrencyNativeName is not supported, it returns CurrencyEnglishName instead, e.g. new RegionInfo("ru-RU").CurrencyNativeName: "Russian Ruble" instead of "рубль".

[ghost]

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[steveisok]

@EgorBo Since we hit a good spot w/ ICU, please update.

[EgorBo]

@steveisok updated the description.

[safern]

@EgorBo might be worth adding these browser limitations into this doc? https://docs.microsoft.com/en-us/dotnet/standard/globalization-localization/globalization-icu

[safern]

@EgorBo @steveisok should we add the list of limitations to the docs I shared above and close this?

[steveisok]

Yeah, I think that’s fine

[marek-safar]

@EgorBo could you please update the documentation page (hit Edit there)

[steveisok]

@EgorBo Since this is for .NET 5, please update the docs so that we can close the issue.

[safern]

This was fixed by: dotnet/docs#20830.

Thanks, @EgorBo