How to reverse strings that contain surrogate pairs in Dart?

I was playing with algorithms using Dart and as I actually followed TDD, I realized that my code has some limitations.

I was trying to reverse strings as part of an interview problem, but I couldn't get the surrogate pairs correctly reversed.

const simple = 'abc';
const emoji = '🍎🍏🐛';
const surrogate = '👮🏽‍♂️👩🏿‍💻';

String rev(String s) {
    return String.fromCharCodes(s.runes.toList().reversed);
}

void main() {
    print(simple);
    print(rev(simple));
    print(emoji);
    print(rev(emoji));
    print(surrogate);
    print(rev(surrogate));
}

The output:

abc
cba
🍎🍏🐛
🐛🍏🍎
👮🏽‍♂️👩🏿‍💻
💻‍🏿👩️♂‍🏽👮

You can see that the simple emojis are correctly reversed as I'm using the runes instead of just simply executing s.split('').toList().reversed.join(''); but the surrogate pairs are reversed incorrectly.

How can I reverse a string that might contain surrogate pairs using the Dart programming language?

When reversing strings, you must operate on graphemes, not characters nor code units. Use grapheme_splitter.