Saku Laesvuori via Guix-patches via <guix-patches@gnu.org> writes:

> * gnu/packages/wm.scm (xmonad)[arguments]: Re-add 'install-xsession phase
>   to enable starting xmonad from a display manager.
>
> Change-Id: I8b29e5a44e9b7a47256a5115e36fb7ff6e0e471a
> ---
>  gnu/packages/wm.scm | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/gnu/packages/wm.scm b/gnu/packages/wm.scm
> index ad74fb5cf7..7ebed1fd67 100644
> --- a/gnu/packages/wm.scm
> +++ b/gnu/packages/wm.scm
> @@ -874,6 +874,23 @@ (define-public xmonad
>      (properties '((upstream-name . "xmonad")))
>      (inputs (list ghc-x11 ghc-data-default-class ghc-setlocale))
>      (native-inputs (list ghc-quickcheck ghc-quickcheck-classes))
> +    (arguments
> +      (list
> +       #:phases
> +       #~(modify-phases %standard-phases
> +           (add-after 'install 'install-xsession
> +             (lambda _
> +               (let ((xsessions (string-append #$output "/share/xsessions")))
> +                 (mkdir-p xsessions)
> +                 (call-with-output-file (string-append xsessions
> +                                                       "/xmonad.desktop")
> +                  (lambda (port)
> +                    (format port "~
> +                     [Desktop Entry]~@
> +                     Name=~a~@
> +                     Comment=xmonad window manager~@
> +                     Exec=~a/bin/xmonad~@
> +                     Type=Application~%" #$name #$output)))))))))

i think can use `make-desktop-entry-file'

>      (home-page "http://xmonad.org")
>      (synopsis "Tiling window manager")
>      (description
>
> base-commit: 20dbf225f332ccc707578263ed710dcf2a8fb78e