[WIP] check ascii_only first fix #9515

[ahaoboy]

Description:

Implements functionality similar to esbuild charset=utf8

https://esbuild.github.io/api/#charset

In old engines like mujs, "\uD83C\uDF0F" is not supported. When ascii_only is false, the expected output is "🌏"

BREAKING CHANGE:
This may cause the default behavior to change, but I don't know how widespread that will be.

Related issue (if exists):

#9515

[changeset-bot]

⚠️ No Changeset found

Latest commit: 38ecc84

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[codspeed-hq]

CodSpeed Performance Report

Merging #9814 will not alter performance

_{Comparing ahaoboy:fix-9515 (5c7624f) with main (7768114)}

Summary

✅ 194 untouched benchmarks

[ahaoboy]

ascii_only	<=es5	output
true	true	"\uD83C\uDF0F"
true	false	"\u{1F30F}"
false	true	"\uD83C\uDF0F"
false	false	"🌏"

if target <= EsVersion::Es5 {
        // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
        let h = ((c as u32 - 0x10000) / 0x400) + 0xd800;
        let l = (c as u32 - 0x10000) % 0x400 + 0xdc00;

        let _ = write!(buf, "\\u{:04X}\\u{:04X}", h, l);
    } else if ascii_only {
        let _ = write!(buf, "\\u{{{:04X}}}", c as u32);
    } else {
        buf.push(c);
    }
} else if ascii_only {
    let _ = write!(buf, "\\u{:04X}", c as u16);
} else {
    buf.push(c);
}

This pr will get the following output

ascii_only	<=es5	output
true	true	"\uD83C\uDF0F"
true	false	"\u{1F30F}"
false	true	"🌏"
false	false	"🌏"