bug#20255: 'search-paths' should respect both user and system profile.

[宋文武 <iyzsong@gmail.com>]

Ludovic Courtès <ludo@gnu.org> writes:

> 宋文武 <iyzsong@gmail.com> skribis:
>
>> Or better to generate a 'profile' script for each manifest, and then
>> merged in shell level, so it can work out-of-the-box. How about:
>>   - /etc/profile:
>>     # configuration for the whole system goes here.
>>     # shouldn't refer profile paths.
>>     export LANG=en_US.utf8
>>     export SSL_CERT_DIR=/etc/ssl/certs
>>     export LINUX_MODULE_DIRECTORY=/run/booted-system/kernel/lib/modules
>>     [...]
>>
>>     source /run/current-system/profile/etc/profile
>>
>>     if [ -f $HOME/.guix-profile/etc/profile ]; then
>>       source $HOME/.guix-profile/etc/profile
>>     fi
>>
>>     # honor setuid-programs
>>     export PATH=/run/setuid-programs:$PATH
>>
>>   - /run/current-system/profile/etc/profile:
>>     export PATH=/run/current-system/profile/bin:/run/current-system/profile/sbin:$PATH
>>     export MANPATH=/run/current-system/profile/share/man:$PATH
>>     [...]
>>     
>>   - ~/.guix-profile/etc/profile:
>>     export PATH=~/.guix-profile/bin:~/.guix-profile/sbin:$PATH
>>     [...]
>
> There’s a further complication here: ‘profile-derivation’, which builds
> the profile, doesn’t know its user-visible name ~/.guix-profile.  It
> just knows its store file name.  However, we don’t want etc/profile to
> read:
>
>   export PATH=/gnu/store/...-profile/bin:$PATH
>
> because then, the user’s environment variables in a running session
> would keep pointing to a given profile generation.
Indeed.  Run guix to install a package should make it available
immediately.  Currently, we have 'PATH=~/.guix-profile/bin' in
profile and print hint for additional variables.
(Note that when profile changes, even we build all variables with the
location they going to be, a hint or re-source is still needed when the
new profile bring new variables.)
>
> So we have to tell ‘profile-generation’ what the user-visible name of
> the profile is going to be.  Attached is a very rough patch to do that.
> This is not so nice because all user interfaces will now have to pass
> that #:target parameter or etc/profile will be “wrong.”
>
> Another option would be to simply run:
>
>   eval `guix package -p ~/.guix-profile --search-paths`
>
> This has two downsides:
>
>   1. It takes ~200 ms to run on my laptop, which can maybe be
>      noticeable; OTOH it’s only for interactive shells, so maybe that’s
>      OK.
>
>   2. If there’s a manifest format change and /etc/profile calls a ‘guix’
>      command that cannot handle the manifest format (because it’s older
>      than the ‘guix’ used to build the profile), then it doesn’t work at
>      all (that’s a bit contrived, but not completely impossible.)
>
> Thoughts?
>
How about using a shell variable as input for the location:
(replace /gnu/store/xxx with $GUIX_PROFILE)

  # etc/profile
  export PATH=$GUIX_PROFILE/bin:$PATH
  export MANPATH=$GUIX_PROFILE/share/man:$MANPATH
  ...

Then when 'source' it, we pass the location:
(we did know where $GUIX_PROFILE is when do the 'source')

  # ~/.bash_profile
  GUIX_PROFILE=$HOME/.guix-profile
  if [ -f $GUIX_PROFILE/etc/profile ]; then
    . $GUIX_PROFILE/etc/profile
  fi

  # /etc/profile
  GUIX_PROFILE=/run/current-system/profile
  source $GUIX_PROFILE/etc/profile