x/text: iterator does not handle zero width joiner

[l0n3star]

What version of Go are you using (go version)?

$ go version 1.20

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

I'm using the go playground

What did you do?

package main

import (
    "fmt"

    "golang.org/x/text/unicode/norm"
)

func main() {
    var ia norm.Iter
    s := "👩🏾‍🦰👱🏾🧑🏾‍⚖️"

    ia.InitString(norm.NFD, s)
    rev := ""

    for !ia.Done() {
        n := ia.Next()
        rev = string(n) + rev
    }

    fmt.Println(rev)
}

Playground: https://go.dev/play/p/Jq9CnUd2zA8

What did you expect to see?

It should print 🧑🏾‍⚖️👱🏾👩🏾‍🦰

I think it has to do with the library not handling zero width joiners. If I use this string: "😀😂" it works as expected.

What did you see instead?

️⚖‍🏾🧑🏾👱🦰‍🏾👩

[mknyszek]

CC @mpvl via https://dev.golang.org/owners

[elliotwutingfeng]

The underlying issue is that x/text doesn't handle multi-rune unicode grapheme clusters.

In the meantime, you could use this third-party module uniseg to iterate through grapheme clusters.