Re: [PATCH] guix package: Add '--switch-generation' option.

[Ludovic Courtès]

Alex Kost <address@hidden> skribis:

> Ludovic Courtès (2014-10-07 20:00 +0400) wrote:
>
>> Alex Kost <address@hidden> skribis:

[...]

>> It’d be enough for me to just call ‘switch-symlinks’ and let it throw
>> ‘system-error’ if something’s wrong.  The exception will be caught, the
>> user will see a “No such file” error, and ‘guix package’ with exit with
>> non-zero (this is done by ‘call-with-error-handling’.)
>
> ‘switch-symlinks’ does not throw an error even if files don't exist, so…

Oh right, ‘symlink’ doesn’t care about its first argument.

>> It’s less informative than what you did, though.  The other option would
>> be to define specific error condition types and throw them from here.
>>
>> WDYT?
>
> … I tried to make it this way, thank you for pointing.  I made another
> commit for adding and using condition types (3 patches are attached
> now).

Great.

> Also I moved ‘process-query’ inside ‘with-error-handling’ (because I
> used ‘raise’ there).  Could there be unwanted consequences after that?

No, I think it’s fine.

> From d5e9abb0395a21e79d4f77181597103d4daf138c Mon Sep 17 00:00:00 2001
> From: Alex Kost <address@hidden>
> Date: Wed, 8 Oct 2014 00:32:28 +0400
> Subject: [PATCH 1/3] profiles: Add condition types for profile and generation.
>
> * guix/profiles.scm (&profile-error, &generation-error): New condition types.
> * guix/ui.scm (call-with-error-handling): Handle these types.
> * guix/scripts/package.scm (roll-back, guix-package): Raise '&profile-error'
>   where needed.

This is bikeshedding, but I would make a hierarchy like this:

                     &profile-error, with ‘profile’ field
                            ^
           .———————————————–+———————————————–.
           |                                 |
  &profile-not-found-error        &missing-generation-error, with ‘generation’ 
field

WDYT?

Other than that the patch looks good.

> From e47644b43aaa73885ca648118b6fc59fdb499303 Mon Sep 17 00:00:00 2001
> From: Alex Kost <address@hidden>
> Date: Wed, 8 Oct 2014 00:39:42 +0400
> Subject: [PATCH 2/3] profiles: Add procedures for switching generations.
>
> * guix/scripts/package.scm (switch-to-previous-generation): Move to...
> * guix/profiles.scm: ... here. Use 'switch-to-generation'.
>   (relative-generation): New procedure.
>   (previous-generation-number): Use it.
>   (switch-to-generation): New procedure.

OK.

> From 003e5c192796e8ea07491a94a85824a533155825 Mon Sep 17 00:00:00 2001
> From: Alex Kost <address@hidden>
> Date: Wed, 8 Oct 2014 00:45:38 +0400
> Subject: [PATCH 3/3] guix package: Add '--switch-generation' option.
>
> * guix/scripts/package.scm: Add '--switch-generation' option.
>   (guix-package): Adjust accordingly.
> * tests/guix-package.sh: Test it.
> * doc/guix.texi (Invoking guix package): Document it.

OK.

Thanks again!

Ludo’.