Why is preffered-width of ListView 0px?

[kermitfrog]

With the following code, the ListView will always be invisible. Debug output tells me that it's preferred-width is 0; Setting alignment to stretch will produce the desired result for me in this case, but I wonder why this is.
I would expect ListView to have a preferred-width based on it's children.

Is this a bug or is there a good reason for this (and if so, which one )?
Is there a way to force it to base it's preferred-width on it's children?

import { ListView, ComboBox, LineEdit, Button, HorizontalBox } from "std-widgets.slint";
export component StrMapEdit inherits HorizontalLayout {
    in-out property <[string]> l: ["A text", "another text"];
    in-out property <[string]> r: ["A text", "another text"];
    in property <[string]> choices: ["A", "B", "C"];

    height: 300px; // just to have room in slintpad
    width: 300px;

    alignment: start;
    
    ListView {
        for key[i] in l: HorizontalLayout {
            LineEdit {
                text: key;
            }

            ComboBox {
                model: choices;
                current-value: r[i];
            }

            Button {
                text: "-";
            }
        }
    }

    Button {
        text: "A button";
    }
}