feat(toHighlight): add ignore-accents support

[J-Sek]

blocks vuetify#22922

[userquin]

We are using toLocaleLowerCase at diacritics, we may have some issue without using i18n lang... that method will use browser/navigator locale.

For example, having en-US at browser and using some german word.

I'm just asking...

[johnleider]

@userquin The API concern is real; the German example isn't.

toLocaleLowerCase() with no argument uses the host locale (browser / Node LANG). That's a problem for a pure utility: same call, different machine, different ranges. SSR is the sharp version — Node locale vs client locale can disagree, so highlighted markup hydrates wrong.

en-US and de lowercase Straße / STRASSE / ß identically. The actual landmine is Turkic I:

'I'.toLowerCase()                   // 'i'          always
'I'.toLocaleLowerCase('tr')         // 'ı'          dotless
'İstanbul'.toLowerCase()            // 'i̇stanbul'  i + combining dot
'İstanbul'.toLocaleLowerCase('tr')  // 'istanbul'

A tr browser and an en-US browser will not highlight the same I / İ / i pairs.

This PR inherited toLocaleLowerCase from master toHighlight. createFilter already uses locale-independent toLowerCase(). The new public findMatchRanges should match that, not the host.

Don't thread useLocale() in here. findMatchRanges is #v0/utilities — no Vue, no plugin. If we ever want German/Turkish-correct case, add an explicit locale?: string later. Silent navigator language is the worst option.

I'll switch both toLocaleLowerCase() calls to toLowerCase(). The İ source map still matters; Unicode default still expands İ to two units.

[userquin]

Maybe we can use 'İstanbul'.normalize('NFD').toLowerCase() (this shouldn't break)

[J-Sek]

'ΣΟΦΟΣ'.toLowerCase() // 'σοφος'
'σοφος'.toUpperCase() // 'ΣΟΦΟΣ'

And apparently it is correct, lol

[userquin]

'ΣΟΦΟΣ'.toLowerCase() // 'σοφος'
'σοφος'.toUpperCase() // 'ΣΟΦΟΣ'

And apparently it is correct, lol

it looks like toLowerCase/toUpperCase is doing its work, there is no need to use normalize('NFD')

[johnleider]

Looking for final comments.