proposal: (define (find-guix-packages list-of-names) ... )

proposal: (define (find-guix-packages list-of-names) ... )

[Florian Paul Schmidt]

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Hi, I found a procedure like this (then at the top of my system
config.scm's) to be quite useful:

diff --git a/gnu/packages.scm b/gnu/packages.scm
index fb27738..63500ab 100644
- --- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -228,6 +228,14 @@ decreasing version order."
                     matching)
             matching)))))

+(define (find-guix-packages list-of-names)
+  (map
+   car
+   (map
+    find-packages-by-name
+    list-of-names)))
+
+
 (define find-newest-available-packages
   (memoize
    (lambda ()


Which could be used in the config like this (for example):

;; Globally-installed packages.
  (packages
   (append
    (find-guix-packages
     '("htop"
       "wget"
       "xmonad"
       "openssh"
       "dmenu"
       "git"
       "xterm"
       "emacs"))
    %base-packages))

and which saves the user from manually entering the use-modules for
the module packages at the top of the config.

I am aware that is maybe still too simplistic. E.g.: It might be good
to check if the name is ambiguous instead of just taking the first
result and throw an error in that case.

As a typical programmer I am allergic to seemingly redundant and
automatable tasks, so I'd love to see something at least similar in
spirit in guix.

Thoughts?

Regards,
Flo


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Re: proposal: (define (find-guix-packages list-of-names) ... )

[Ludovic Courtès]

Florian Paul Schmidt <mista.tapas@gmx.net> skribis:

> +(define (find-guix-packages list-of-names)
> +  (map
> +   car
> +   (map
> +    find-packages-by-name
> +    list-of-names)))

[...]

> I am aware that is maybe still too simplistic. E.g.: It might be good
> to check if the name is ambiguous instead of just taking the first
> result and throw an error in that case.

Indeed.  ;-)

> As a typical programmer I am allergic to seemingly redundant and
> automatable tasks, so I'd love to see something at least similar in
> spirit in guix.

I can sympathize with this.

I think ‘specification->package’ from (gnu packages) is the procedure
you want.  Like this:

  (map specification->package
       '("guile-2" "gnupg-2.0" "coreutils"))

It emits a warning in case the specification is ambiguous.

Maybe we could/should use it in the example GuixSD configurations, and
at least document it somewhere.

WDYT?

Thanks,
Ludo’.

Re: proposal: (define (find-guix-packages list-of-names) ... )

[Florian Paul Schmidt]

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Hi, and thanks for your reply..

On 11/15/2015 09:35 PM, Ludovic Courtès wrote:

> I think ‘specification->package’ from (gnu packages) is the
> procedure you want.  Like this:
> 
> (map specification->package '("guile-2" "gnupg-2.0" "coreutils"))
> 
> It emits a warning in case the specification is ambiguous.
> 
> Maybe we could/should use it in the example GuixSD configurations,
> and at least document it somewhere.
> 
> WDYT?

Sounds like a plan. Though in this use-case I think I'd prefer an
error over a warning. For the simple reason that during system
reconfigure a warning might be missed easily. Especially after a guix
pull where suddenly a package spec might become ambiguous where it
wasn't before and a different package gets chosen.

OTOH, maybe that's overdoing it and even with the error instead of a
warning there are still some failure modes somewhat similar to this:
E.g. Package foo disappears while a quite different package foo
appears (possibly in a different module). Quite unlikely but possible.


Regards,
Flo

P.S.: Note though that there are modes like this also for the now
common practice of using use-modules in a non-local way at the top of
the config file but they are more contrived (and depend on having just
the right use-modules calls and packages in the packages list).

I'm new to guile (and scheme and guix ;), but maybe there's a way to
use use-modules in a more local fashion. Together with the guarantee
that the module/package combination is unique (not including version
changes which are to be expected during a reconfigure after a guix
pull) it would be possible to avoid those kind of surprises if needed.


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Re: proposal: (define (find-guix-packages list-of-names) ... )

[Ludovic Courtès]

Florian Paul Schmidt <mista.tapas@gmx.net> skribis:

> Hi, and thanks for your reply..
>
> On 11/15/2015 09:35 PM, Ludovic Courtès wrote:
>
>> I think ‘specification->package’ from (gnu packages) is the
>> procedure you want.  Like this:
>>
>> (map specification->package '("guile-2" "gnupg-2.0" "coreutils"))
>>
>> It emits a warning in case the specification is ambiguous.
>>
>> Maybe we could/should use it in the example GuixSD configurations,
>> and at least document it somewhere.
>>
>> WDYT?
>
> Sounds like a plan. Though in this use-case I think I'd prefer an
> error over a warning. For the simple reason that during system
> reconfigure a warning might be missed easily. Especially after a guix
> pull where suddenly a package spec might become ambiguous where it
> wasn't before and a different package gets chosen.
>
> OTOH, maybe that's overdoing it and even with the error instead of a
> warning there are still some failure modes somewhat similar to this:
> E.g. Package foo disappears while a quite different package foo
> appears (possibly in a different module). Quite unlikely but possible.

There’s a range of options here: referring to variables by name (this is
best, you get an error if you got the name wrong, etc.; downside is you
need to know what modules to import), using ‘specification->package’, or
using something like what you suggested initially.

I’m fine with documenting ‘specification->package’ as an alternate
option.  Its semantics are exactly the same as when referring to a
package by name on the command line (a warning if it’s ambiguous, not an
error), which seems reasonable.

Thoughts?

Ludo’.

Re: proposal: (define (find-guix-packages list-of-names) ... )

[Florian Paul Schmidt]

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Hash: SHA256

On 11/16/2015 02:03 PM, Ludovic Courtès wrote:
> Florian Paul Schmidt <mista.tapas@gmx.net> skribis:
> 
> I’m fine with documenting ‘specification->package’ as an alternate 
> option.  Its semantics are exactly the same as when referring to a 
> package by name on the command line (a warning if it’s ambiguous,
> not an error), which seems reasonable.
> 
> Thoughts?
> 

Hi again,

sure, I'm fine with just a warning, too. Thought I'd just mention the
possible problems that exist. If you want to, I can try and put
together a patch for the docs..

Regards,
Flo


- -- 
https://fps.io
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Re: proposal: (define (find-guix-packages list-of-names) ... )

[Ludovic Courtès]

Florian Paul Schmidt <mista.tapas@gmx.net> skribis:

> sure, I'm fine with just a warning, too. Thought I'd just mention the
> possible problems that exist. If you want to, I can try and put
> together a patch for the docs..

Sure.  I think we would need a new section for (gnu packages), maybe
“Distribution API” under “GNU Distribution”?  It would describe
‘fold-packages’, ‘specification->package’, and so on.

Thanks,
Ludo’.

Re: proposal: (define (find-guix-packages list-of-names) ... )

[Florian Paul Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1777 bytes --]

On Mon, 16 Nov 2015 21:06:00 +0100
ludo@gnu.org (Ludovic Courtès) wrote:

> Sure.  I think we would need a new section for (gnu packages), maybe
> “Distribution API” under “GNU Distribution”?  It would describe
> ‘fold-packages’, ‘specification->package’, and so on.

Let's start smaller :) [I'm still fighting with emacs - I gave it many 
chances over the years, but we'll never find true happy puppies' love -
and a few other things...]

--snip
diff --git a/doc/guix.texi b/doc/guix.texi
index 3b6955c..32bedd7 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5482,6 +5482,25 @@ above, such as @code{host-name} and @code{bootloader}, are mandatory.
 Others, such as @code{packages} and @code{services}, can be omitted, in
 which case they get a default value.
 
+The attentive reader might have noticed that the @code{tcpdump} package
+is defined in the @code{gnu packages admin} module. While it is generally
+encouraged to install packages in users' profiles it might be
+necessary to install a few more packages in the base system. Maintaining
+the list of used modules (and figuring out which are the correct
+ones) can become a burden and error prone. But the system configuration
+is a lisp program, so we can make use of the power of lisp to automate
+this task. The @code{gnu packages} module provides the
+@code{specification->package} procedure which can help us here:
+
+@lisp
+  ;; Globally-installed packages.
+  (packages
+     (append
+        (map (specification->package
+                `("tcpdump" "emacs" "htop" "tmux")))
+        %base-packages))
+@end lisp
+
 @vindex %base-packages
 The @code{packages} field lists
 packages that will be globally visible on the system, for all user
--snip

[-- Attachment #2: guix.texi.diff --]
[-- Type: application/octet-stream, Size: 1263 bytes --]

diff --git a/doc/guix.texi b/doc/guix.texi
index 3b6955c..32bedd7 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5482,6 +5482,25 @@ above, such as @code{host-name} and @code{bootloader}, are mandatory.
 Others, such as @code{packages} and @code{services}, can be omitted, in
 which case they get a default value.
 
+The attentive reader might have noticed that the @code{tcpdump} package
+is defined in the @code{gnu packages admin} module. While it is generally
+encouraged to install packages in users' profiles it might be
+necessary to install a few more packages in the base system. Maintaining
+the list of used modules (and figuring out which are the correct
+ones) can become a burden and error prone. But the system configuration
+is a lisp program, so we can make use of the power of lisp to automate
+this task. The @code{gnu packages} module provides the
+@code{specification->package} procedure which can help us here:
+
+@lisp
+  ;; Globally-installed packages.
+  (packages
+     (append
+        (map (specification->package
+                `("tcpdump" "emacs" "htop" "tmux")))
+        %base-packages))
+@end lisp
+
 @vindex %base-packages
 The @code{packages} field lists
 packages that will be globally visible on the system, for all user

Re: proposal: (define (find-guix-packages list-of-names) ... )

[Ludovic Courtès]

Florian Paul Schmidt <mista.tapas@gmx.net> skribis:

> On Mon, 16 Nov 2015 21:06:00 +0100
> ludo@gnu.org (Ludovic Courtès) wrote:
>
>> Sure.  I think we would need a new section for (gnu packages), maybe
>> “Distribution API” under “GNU Distribution”?  It would describe
>> ‘fold-packages’, ‘specification->package’, and so on.
>
> Let's start smaller :)

I rearranged the text and ended up with something different from your
original patch but hopefully as informative in f6c9fb1.

Thanks,
Ludo’.

Re: proposal: (define (find-guix-packages list-of-names) ... )

[Florian Paul Schmidt]

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Hash: SHA256

On 11/28/2015 04:39 PM, Ludovic Courtès wrote:

>> Let's start smaller :)
> 
> I rearranged the text and ended up with something different from
> your original patch but hopefully as informative in f6c9fb1.

And more concise :)

Thanks,
Flo


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https://fps.io
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