Hartmut Goebel <h.goebel@crazy-compilers.com> writes:

> Hi,
>
> it came to my mind that currently the qt-build-system wraps the program
> without passing along any environment variables. Thus e.g.
> XDG_CONFIG_DIRS will be overwritten, instead of not extended. Furtunatly
> ((guix build utils) wrap-program) supports prefixing or suffixing an
> existing variable value.
>
> Shall qt-build-system: prefix or suffix existing env-variables? Should
> it become
>
>     export
> XDG_DATA_DIRS="$XDG_DATA_DIRS${XDG_DATA_DIRS:+:}/gnu/store/…-kate-…"
>
> or
>
>     export
> XDG_DATA_DIRS="/gnu/store/…-kate-…${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"

Note that XDG Base Directory Specification [1] sets default values to
use for empty or unset XDG_* variables, for instance:

  "If $XDG_DATA_DIRS is either not set or empty, a value equal to
  /usr/local/share/:/usr/share/ should be used."

So the correct way to extend XDG_DATA_DIRS would be

  export XDG_DATA_DIRS="${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}:/gnu/store/…-kate-…"

or

  export XDG_DATA_DIRS="/gnu/store/…-kate-…:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}"

[1] https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

--
Mikhail