Why convert locales to lowercase in methods like setLocaleFromQuery()?

[leohihimax]

Some methods like setLocaleFromQuery(), setLocaleFromCookie() will convert the locale to lower case. I see a lot of projects use uppercase letter in their i18n locales file name like en-US.json, zh-CN.json.
Also, the accept language in HTTP request header use the uppercase letter in the locale like en,zh-CN;q=0.8,zh;q=0.6.
So my question is why those methods convert locales to lowercase? Why not just keep the original case?

[gjuchault]

Maybe @jeresig can answer to this (he wrote/forked this code)

[holm]

I've just run into the same problem after upgrading. We use uppercase for the country part, which now means it won't match f.ex. zh-CN. Not sure how this could be resolved, but ideally it would case-insensitive.