[bug#36021] [PATCH] search-paths: 'environment-variable-definition' output for fish

[Dan Frumin <dfrumin@cs.ru.nl>]

Hi Meiyo,

On 03-06-19 07:51, Meiyo Peng wrote:
> Hi Dan,
> 
> Dan Frumin writes:
> 
>> Some background on this patch:
>> Right now whenever I do any Guix operation that requires me to modify
>> environment variables (e.g. installing a Guile library requires me to update
>> $GUILE_LOAD_PATH afterwards), Guix helpful tells me what commands I have to run
>> to update the variables.
>>
>> However, those commands are currently in bash/POSIX(?) format `export
>> VAR=VALUE`. I've modified the `environment-variable-definition` function to
>> support the syntax for Fish shell as well. I don't know if this method of
>> looking at the $SHELL variable is sound, but it works  on my machine.
>>
>> Documentation for the `set' function in Fish: https://fishshell.com/docs/current/commands.html#set
>>
>> PS: this is my first non-package patch for Guix so I apologize if there is something wrong with the patch
> 
> I think this patch will cause more trouble than good.  Does this patch
> replaces etc/profile with fish syntax script?  etc/profile is supposed
> to be in POSIX shell syntax.  Fish shell has it's own configuration
> files in /etc/fish/config.fish and /etc/fish/conf.d/*.fish.  If you
> really want to generate fish syntax scripts, please put them in
> /etc/fish/config.fish or /etc/fish/conf.d/*.fish.
> 

No, this patch doesn't touch etc/profile in any way, it is only concerned with the output that you get from `guix package` on your terminal.
So I guess it's kind of orthogonal to the upgraded fish package that you made?

> See:
> 1. https://lists.gnu.org/archive/html/guix-devel/2019-01/msg00071.html
> 2. https://lists.gnu.org/archive/html/guix-devel/2019-01/msg00333.html
> 3. https://issues.guix.gnu.org/issue/34153
> 
> Have you tried the fish-foreign-env package?  You can source bash
> scripts in fish via `fenv source ~/.guix-profile/etc/profile`.  That's how
> the fish shell in Guix set up environment variables upon login.
> 

Thanks! This is quite nice, I should upgrade my Fish installation.

> Perhaps we can handle this better.  Do you have any suggestions?  My
> idea:
> 
> 1. The fish-foreign-env package is very useful but it's not installed by
> default in order to avoid polluting user's profiles according to the
> Guix convention.  In this case I think it's a useful utility rather than
> pollution.  Do you want it to be installed together with the fish
> package by default?

Well, you added it as part of the fish dependency, right? I think it makes sense, especially on Guix SD.

> 
> 2. etc/profile is supposed to be sourced by a login shell.  And we
> should avoid sourcing it from a non-login shell.  That's why I made the
> fish package in Guix only sources it upon login.  That means starting a
> new fish shell won't source it automatically.  So please source it
> manually if you need the new environment variables (fenv source
> ~/.guix-profile/etc/profile).

I am not knowledgeable enough to comment on this, but it seems to me that it is done similarly if you are using bash: e.g. you have to source the 
profile yourself if you want to get it in a non-login shell.

> 
> 3. We can write better documentations explaining how to deal with fish
> shell in Guix.  There's an old discussion about having a Guix wiki or
> a Guix book.
> 

Yeah, more documentation is always better :)

Best regards,
-Dan

> 
> --
> Meiyo Peng
> https://www.pengmeiyu.com/
>