debugging xsession xmonad plasma5

gistfile1.txt

When I launch "plasma5+xmonad" it no longer launches xmonad but stays with kwin.
this is after an update that told me xserver settings were deprecated so maybe something happened there.

# current system works
17:33:58 [kiwi@mvp-nixos ~]$ echo $(cat /nix/var/nix/profiles/system-296-link/nixos-version )
20.03pre205780.d942688fc13
17:34:02 [kiwi@mvp-nixos ~]$ echo $(cat /run/current-system/nixos-version )
20.03pre205780.d942688fc13
#this and subsequent ones do not
17:34:44 [kiwi@mvp-nixos ~]$ echo $(cat /nix/var/nix/profiles/system-297-link/nixos-version )
20.03pre206438.a06925d8c60
17:34:55 [kiwi@mvp-nixos ~]$

gistfile2.txt

22:10:50 [kiwi@mvp-nixos nixpkgs]$ git bisect bad
8dc5ff7dcfd1c58c32004ffae25e6d31ed83d86c is the first bad commit
commit 8dc5ff7dcfd1c58c32004ffae25e6d31ed83d86c
Author: Jan Tojnar <jtojnar@gmail.com>
Date:   Tue Dec 10 15:10:30 2019 +0100

    nixos/displayManager: deprecate separate options for default wm/dm

    The upstream session files display managers use have no concept of sessions being composed from
    desktop manager and window manager. To be able to set upstream session files as default
    session, we need a single option. Having two different ways to set default session would be confusing,
    though, so we decided to deprecate the old method.

    We also created separate script for each session, just like we already had a separate desktop
    file for each one, and started using displayManager.sessionPackages mechanism to make the
    session handling more uniform.

 nixos/doc/manual/configuration/x-windows.xml       |   3 +-
 nixos/doc/manual/configuration/xfce.xml            |   5 +-
 nixos/doc/manual/release-notes/rl-2003.xml         |  13 ++
 nixos/lib/testing-python.nix                       |   3 +-
 nixos/lib/testing.nix                              |   3 +-
 .../services/x11/desktop-managers/default.nix      |  23 +-
 .../services/x11/desktop-managers/pantheon.nix     |   2 +
 .../x11/display-managers/account-service-util.nix  |  39 ++++
 .../services/x11/display-managers/default.nix      | 231 +++++++++++----------
 .../modules/services/x11/display-managers/gdm.nix  |  62 ++----
 .../x11/display-managers/lightdm-greeters/mini.nix |   5 +-
 .../services/x11/display-managers/lightdm.nix      |  33 +--
 .../modules/services/x11/display-managers/sddm.nix |  16 +-
 .../services/x11/window-managers/default.nix       |  15 +-
 nixos/tests/common/x11.nix                         |   8 +-
 nixos/tests/i3wm.nix                               |   2 +-
 nixos/tests/lightdm.nix                            |   3 +-
 nixos/tests/plasma5.nix                            |   2 +-
 nixos/tests/sddm.nix                               |   6 +-
 nixos/tests/xmonad.nix                             |   4 +-
 20 files changed, 254 insertions(+), 224 deletions(-)
 create mode 100644 nixos/modules/services/x11/display-managers/account-service-util.nix
22:11:49 [kiwi@mvp-nixos nixpkgs]$