Support non-Gregorian calendars in @formatjs/intl-datetimeformat

[meness]

Which package?

@formatjs/intl-datetimeformat

Describe the bug

Importing @formatjs/intl-datetimeformat throws an exception for fa locale in iOS.

Error: [@formatjs/intl Error FORMAT_ERROR] Error formatting date.

undefined is not an object (evaluating 'formats[0]')

BestFitFormatMatcher

InitializeDateTimeFormat

[native code]

variadic

variadic@[native code]

formatDate

To Reproduce

1. Open the link below in your iPhone, no matter you use Safari or Chrome.
2. Check the console for the exception

Expected behavior

It should work as expected, displays a simple date.

Screenshots

Please check this out on iOS: https://codesandbox.io/s/datetimeformat-polyfill-ios-exception-for-fa-locale-jj5sn

Smartphone (please complete the following information):

• Device: iPhone
• OS: iOS 14.0.1
• Browser: Safari and Chrome
• Version: Chrome v85.0.4183.109

Additional context

I tested this with the latest Chrome and iOS versions, and get the same exception. It works fine on Desktop.

[longlho]

this is bc fa by default uses persian calendar which right now we don't support, setting calendar: "gregory" would fix this. I have to look into where persian calendar data lives

[dvoong-lyra]

setting calendar: "gregory" would fix this

We are using react-intl with this polyfill and want to avoid passing { calendar: "gregory" } at every call-site (formatDate, etc). Should it work if we specified -u-ca-gregory in the locale string? I tried this but it still throws here. I'm not familiar with the locale data internals so I am not sure if this is possible, but it seems to be the browser Intl behavior

Edit: I did some digging on this and I found that this is because the BestFitMatcher is not returning an extension in the result after resolving the locale. I may put up a PR for this.