[bug#50982] [PATCH] scripts: home/system: Don’t throw an error if no generations exist.

[Xinglu Chen <public@yoctocell.xyz>]

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Hi,

On Sun, Oct 03 2021, Maxime Devos wrote:

> Xinglu Chen schreef op za 02-10-2021 om 23:05 [+0200]:
>> Previously, When running ‘guix home describe’ or ‘guix system describe’ prior
>> to having any generations, a backtrace would produced.  Since not having any
>> existing generations is not an error, a warning would be enough.
>> 
>>   $ guix system describe
>>   guix system: warning: no system generation, nothing to describe
>
> Printing a warning instead of an error to avoid a backrace isn't necessary.
> E.g., "guix show i-do-not-exists" prints an error
> ‘guix show: error: i-do-not-exist: package not found’.
>
> I suggest using (leave (G_ "bla bla")) instead of (error (G_ "bla bla"))
> for these kind of errors, it appears to work '%find-package' in (gnu packages).
>
> I don't know if the output of "guix system describe" and "guix home describe"
> should be an error or warning here ...

Hmm, since I don’t think that not having any generations is an error, I
would say it makes more sense to use ‘warning’ instead of ‘leave’.
‘leave’ would signal that something isn’t correct, which makes sense if
one runs ‘guix show doesnt-exist’, but not having any generations
doesn’t really mean that something is wrong.

WDYT?

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