locale negotiation is incorrect for i18n routing

[longlho]

Bug report

Describe the bug

If I send Accept-Language: "fr-XX,en" and I have available locales fr, en, it should give me fr instead of en (current behavior)

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

Should be routed to fr

Screenshots

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System information

• OS: [e.g. macOS, Windows]
• Browser (if applies) [e.g. chrome, safari]
• Version of Next.js: [e.g. 6.0.2]
• Version of Node.js: [e.g. 10.10.0]

Additional context

Add any other context about the problem here.

[longlho]

this might be something formatjs can provide actually

[longlho]

@Timer I believe u can use the ResolveLocale abstract operation from ECMA402 (spec). We do have an implementation in @formatjs/ecma402-abstract: https://codesandbox.io/s/affectionate-chatelet-nvgl7?file=/src/App.tsx

ResolveLocale(
	["fr", "en"],
	["fr-XX", "en"],
	{ localeMatcher: "best fit" },
	[],
	{},
	() => "en"
)

should yield

{
	"locale":"fr",
	"dataLocale":"fr"
}

[arguiot]

I have the same issue here... very very annoying.