How to stop repeated letter entry in TMP input field when key held down in Unity

Question

I'm using a TMP input field and would like to override some default behaviour. Specifically, when a letter is held down, it repeats. Similarly, when backspace (or delete) is held down, it removes multiple characters.

I would like it so that if a letter is held down, that letter is only entered once. I would also like backspace to only remove one character if it is held down.

I am already implementing Input.GetKeyDown() to perform a certain task, so I believe I will need to do something similar here, but I can't quite work out how.

Thanks.

---

EDIT:

Thanks @daniel-m. This works sometimes, but other times it allows for 1 or 2 repeating letters.

I added extra Debug.Logs to investigate, like so:

private void Update()
    {
        if (IsFieldSelected)
        {
            // if a key is pressed
            if (Input.anyKeyDown)
            {
                // save the the current text to lastText (this key will have been entered)
                lastText = inputField.text;
                Debug.Log("Key was pressed! inputField = " + inputField.text + ", inputField = " + lastText);
            }

            // if a key is held down
            if (Input.anyKey)
            {
                Debug.Log("Key held down, part 1! inputField = " + inputField.text + ", inputField = " + lastText);
                inputField.text = lastText;
                Debug.Log("Key held down, part 2! inputField = " + inputField.text + ", inputField = " + lastText);
            }
        }
    }

And I held down the keys the keys 1 to 6 consecutively with the following Keydown and Keyup timestamps (recorded in a different script):

The output into the text box was 1122334456. You can see in the debug logs below that a repetition is added to the inputField.text. However, it doesn't always show up in the input field - numbers 1-4 repeated but 5 and 6 didn't. And when the numbers do repeat, they don't show up in the input field until the key is released (even though the debug log says it's already in there).

Answer 1

I have tested a little bit around and I think I have a solution for your problem.
When a key is pressed I save the current text into lastText. If a key is held down I set the current text inside the input field to lastText. So the code essentially sets the text field to the last text that was saved.

public class Text : MonoBehaviour
{
    public TMP_InputField inputField;
    private bool IsFieldSelected;
    private string lastText;

    private void Update()
    {
        if (IsFieldSelected)
        {
            if (Input.anyKeyDown)
            {
                lastText = inputField.text;
            }

            if (Input.anyKey)
            {
                Debug.Log(inputField.text);
                inputField.text = lastText;
            }
        }
    }

    public void IsSelected()
    {
        IsFieldSelected = true;
    }

    public void IsNotSelected()
    {
        IsFieldSelected = false;
    }
}

These are the events inside the InputField (TMP) gameobject.