[bug#59983] home: Let user configure XDG base directories.

* gnu/home.scm (home-environment)[base-xdg-configuration]: New field.
* gnu/home/services/xdg.scm (ensure-xdg-base-dirs-on-activation): Make
XDG_RUNTIME_DIR directory if the configuration changes it from the default.
---
Allows making a runtime dir at ~/.local/runtime (or any other dir),
so users don't have to set up elogind or other greeters/PAM modules.

 gnu/home.scm              | 9 +++++++--
 gnu/home/services/xdg.scm | 7 ++++++-
 2 files changed, 13 insertions(+), 3 deletions(-)

On 2022-12-12 03:00, Antero Mejr via Guix-patches via wrote:

> * gnu/home.scm (home-environment)[base-xdg-configuration]: New field.
> * gnu/home/services/xdg.scm (ensure-xdg-base-dirs-on-activation): Make
> XDG_RUNTIME_DIR directory if the configuration changes it from the default.
> ---
> Allows making a runtime dir at ~/.local/runtime (or any other dir),
> so users don't have to set up elogind or other greeters/PAM modules.
>
>  gnu/home.scm              | 9 +++++++--
>  gnu/home/services/xdg.scm | 7 ++++++-
>  2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/gnu/home.scm b/gnu/home.scm
> index c95d1e0818..f100b575e3 100644
> --- a/gnu/home.scm
> +++ b/gnu/home.scm
> @@ -39,6 +39,7 @@ (define-module (gnu home)
>              home-environment-essential-services
>              home-environment-services
>              home-environment-location
> +            home-environment-base-xdg-configuration
>  
>              home-environment-with-provenance
>  
> @@ -71,7 +72,10 @@ (define-record-type* <home-environment> home-environment
>    (location           home-environment-location            ; <location>
>                        (default (and=> (current-source-location)
>                                        source-properties->location))
> -                      (innate)))
> +                      (innate))
> +
> +  (base-xdg-configuration home-environment-base-xdg-configuration
> +                          (default (home-xdg-base-directories-configuration))))
>  
>  (define (home-environment-default-essential-services he)
>    "Return the list of essential services for home environment."
> @@ -83,7 +87,8 @@ (define (home-environment-default-essential-services he)
>     (service home-symlink-manager-service-type)
>  
>     (service home-fontconfig-service-type)
> -   (service home-xdg-base-directories-service-type)
> +   (service home-xdg-base-directories-service-type
> +            (home-environment-base-xdg-configuration he))

This change is not needed, you can set xdg dirs by extending
home-xdg-base-directories-service-type with adjusted
home-xdg-base-directories-configuration.

>     (service home-shell-profile-service-type)
>  
>     (service home-service-type)
> diff --git a/gnu/home/services/xdg.scm b/gnu/home/services/xdg.scm
> index 865f8b81d7..b62580461e 100644
> --- a/gnu/home/services/xdg.scm
> +++ b/gnu/home/services/xdg.scm
> @@ -133,7 +133,12 @@ (define (ensure-xdg-base-dirs-on-activation config)
>                          (configuration-field-name field) 'upper))))
>                   ;; XDG_RUNTIME_DIR shouldn't be created during activation
>                   ;; and will be provided by elogind or other service.
> -                 (and (not (string=? "XDG_RUNTIME_DIR" variable))
> +                 ;; But if the user changes the value from the default,
> +                 ;; then we can make XDG_RUNTIME_DIR.
> +                 (and (or (not (string=? "XDG_RUNTIME_DIR" variable))
> +                          (not (string=? ((configuration-field-getter field)
> +                                          config)
> +                                         "${XDG_RUNTIME_DIR:-/run/user/$UID}")))
>                        variable)))
>               home-xdg-base-directories-configuration-fields)))

There is no way to understand upfront if directory containing
XDG_RUNTIME_DIR is writable and this is why it's a good idea to delegate
initialization of it to external thing and never try to create it here,
even if it has non-default value.

But in case you are sure it's writable and want to ensure the directory
created, just be this thing managing and providing XDG_RUNTIME_DIR and
extend activation script with the following G-expression:

#~(mkdir-p (getenv "XDG_RUNTIME_DIR"))

The full snippet:

--8<---------------cut here---------------start------------->8---
(simple-service
 'ensure-xdg-runtime-dir-exists
 home-activation-service-type
 #~(mkdir-p (getenv "XDG_RUNTIME_DIR")))
--8<---------------cut here---------------end--------------->8---

Andrew Tropin <andrew@trop.in> writes:
> There is no way to understand upfront if directory containing
> XDG_RUNTIME_DIR is writable and this is why it's a good idea to delegate
> initialization of it to external thing and never try to create it here,
> even if it has non-default value.

Thank you for the snippet, that's a much better way of fixing my issue.

I still think guix home should (by default) be able to use all its
features without the requirement of having external programs installed.

For example, suppose you have a server that you want to set up your home
environment on, for when you login to do sysadmin tasks. That server
wouldn't have %desktop-services (elogind), nor would it have a custom
greeter like greetd. So XDG_RUNTIME_DIR will be unset.

If XDG_RUNTIME_DIR does not exist, can we make a fallback path to have
guix home put the shepherd socket and on-first-login-executed flag file
in ~/.local/var/run (or somewhere else writable) instead?

On 2022-12-13 15:53, Antero Mejr wrote:

> Andrew Tropin <andrew@trop.in> writes:
>> There is no way to understand upfront if directory containing
>> XDG_RUNTIME_DIR is writable and this is why it's a good idea to delegate
>> initialization of it to external thing and never try to create it here,
>> even if it has non-default value.
>
> Thank you for the snippet, that's a much better way of fixing my issue.
>
> I still think guix home should (by default) be able to use all its
> features without the requirement of having external programs installed.
>
> For example, suppose you have a server that you want to set up your home
> environment on, for when you login to do sysadmin tasks. That server
> wouldn't have %desktop-services (elogind), nor would it have a custom
> greeter like greetd. So XDG_RUNTIME_DIR will be unset.
>
> If XDG_RUNTIME_DIR does not exist, can we make a fallback path to have
> guix home put the shepherd socket and on-first-login-executed flag file
> in ~/.local/var/run (or somewhere else writable) instead?

Without automatic cleanup (which is the case for elogind, pam_rundir and
other options providing XDG_RUNTIME_DIR) it will likely missbehave.

It's much trickier than it seems on the first sight.  Theoretically it's
possible, but requires a lot of additional work to do it right.

In fact on-first-login script is a kinda hack to make shepherd started
somehow, but running user's shepherd is tricky on its own.  Shutting it
down correctly (and all the processes managed by it) is even more
challenging.  AFAIK, there is no easy and straightforward solution (even
in other init systems that we can quickly borrow), so it will require
time and effort to carefully design and implement it.

If you want to work on it - send you ideas, research and patches for the
possible solutions, I'll share my input :)