Re: [PATCH 2/2] emacs: Add 'guix-package-from-file' command.

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> Ludovic Courtès (2016-05-08 21:40 +0300) wrote:

[...]

>> … by wrapping ‘vhash-consq’ in ‘delay’.
>
> … I tried it, but I got an error I don't know what to do with:
>
>   Throw to key `vm-error' with args `(vm-run "VM: Stack overflow" ())'.

I needs to be changed like this:

--8<---------------cut here---------------start------------->8---
(define-values (package-by-address
                register-package)
  (let ((table (delay (fold-packages
                       (lambda (package table)
                         (vhash-consq (object-address package)
                                      package table))
                       vlist-null))))
    (values
     (lambda (address)
       "Return package by its object ADDRESS."
       (match (vhash-assq address (force table))
         ((_ . package) package)
         (_ #f)))
     (lambda (package)
       "Register PACKAGE by its 'object-address', so that later
'package-by-address' can be used to access it."
       (let ((table (force table)))
         (set! table
           (delay (vhash-consq (object-address package)
                               package table))))))))
--8<---------------cut here---------------end--------------->8---

In the example you posted, ‘register-package’ would turn ‘table’ into a
self-reference, hence the stack overflow.

>> To avoid ‘set!’ above, the options that come to mind would be:
>>
>>   1. To not provide M-x guix-package-from-file and instead provide, say,
>>      M-x guix-install-package-from-file.  That way, we wouldn’t need to
>>      remember the package.
>
> I don't like this solution.  With "M-x guix-package-from-file" you get a
> full-featured *Guix Package Info* buffer, where you can not only install
> the package, but download its source, look at its license, inputs,
> etc. (and soon it will be possible just to build it without installing).

Yeah, I mentioned it for completeness but I don’t like it either.

Thanks!

Ludo’.