Switching layouts stops on German Neo2 if it's not the first layout

[bam80]

So if we have German, Neo 2 variant as the first layout - it switches to the next just fine, and then by the loop:
Neo 2 <- -> US

If we just change the order, switching stops on Neo:
US (X) <- -> (OK) Neo 2
or
US -> (OK) Neo 2 -> (X) UK

Tested with CapsLock and RCtl+RShift as group switchers, on both Gnome and Plasma, Wayland and X11 sessions.
Downstream report: https://bugs.kde.org/show_bug.cgi?id=432436

[bluetech]

I am able to reproduce this with:

sudo ./build/xkbcli-interactive-evdev --layout 'us,de' --variant ,neo --option grp:rctrl_rshift_toggle

RCtrl + RShift toggles to Neo, but another time doesn't. The problem is some conflict on how the modifiers are used. Particularly, commenting out this line in the de(neo) map makes it work:

https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/blob/aeed643124d761c85c55bb2668162afd7bca55b9/symbols/de#L558

    include "shift(both_capslock)"

Note:

$ xkbcli list | grep shift:both_capslock::
  - shift:both_capslock::Both Shift together enable Caps Lock

I don't have time to check it in any more depth ATM, but I suggest reporting this to xkeyboard-config because it's probably not something on the xkbcommon (keymap compiling/interpretation) side.

[bam80]

Thank you for your investigation Ran!
I've crossposted it here: https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/issues/252

[bluetech]

I'll close this now, but feel free to reopen if it's something xkbcommon can help with.