[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

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[CLAassistant]

All committers have signed the CLA.

[codspeed-hq]

CodSpeed Performance Report

Merging #9814 will degrade performances by 2.21%

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

Summary

❌ 1 regressions
✅ 193 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	es/full/codegen/es2017	253.2 µs	259 µs	-2.21%

[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	"🌏"