Re: [PATCH 2/4] emacs: Add 'guix-devel-download-package-source'.

[Alex Kost <alezost@gmail.com>]

Ludovic Courtès (2015-10-04 19:57 +0300) wrote:

> Alex Kost <alezost@gmail.com> skribis:
>
>> Ludovic Courtès (2015-10-03 23:35 +0300) wrote:
>>
>>> Alex Kost <alezost@gmail.com> skribis:
>>>
>>>> * emacs/guix-devel.el (guix-devel-setup-repl): Use (guix packages) module.
>>>>   (guix-devel-download-package-source): New command.
>>>>   (guix-devel-keys-map): Add key binding for it.
>>>> * doc/emacs.texi (Emacs Development): Document it.
>>>
>>> [...]
>>>
>>>> +(defun guix-devel-download-package-source ()
>>>> +  "Download the source of the current package.
>>>> +Use this function to compute SHA256 hash of the package source."
>>>> +  (interactive)
>>>> +  (guix-devel-with-definition def
>>>> +    (guix-devel-use-modules "(guix scripts download)")
>>>> +    (when (or (not guix-operation-confirm)
>>>> +              (y-or-n-p (format "Download '%s' package source?" def)))
>>>> +      (guix-geiser-eval-in-repl
>>>> +       (format "(guix-download (origin-uri (package-source %s)))"
>>>> +               def)))))
>>>
>>> What about instead building the ‘package-source-derivation’ of the
>>> package?  That way, that would do the exact same thing as ‘guix build
>>> -S’ and would work not only with ‘url-fetch’ but also with the other
>>> things.
>>>
>>> WDYT?
>>
>> The goal of this command is to display a hash.
>
> So this would be something one would use as they write a package
> definition, to fill in the ‘sha256’ field, right?

Exactly.  For example, here is how I update a package using Geiser:

- I modify its 'version' field,
- "C-M-x" to reevaluate the package definition,
- "C-c . s" to download the new source and show its hash,
- replace the old hash with the new one,
- and finally "C-c . b" to build the new version of package.

> In that case, I would suggest something based on the URL at point rather
> than the origin at point.

It's neither URL at point, nor origin at point: it's like "C-c . b" but
to download the source of the current package definition instead of
building it.

Also I don't understand how it can be based on the URL at point as
instead of the full URL, we have something like this:

  (uri (string-append "http://.../foo-" version ".tar.xz"))

So currently to use "guix download", at first you need to manually
construct the full URL.  I find this inconvenient, that's why I want to
have a command to download a source of the current package and to
display its hash.

> However, if this is “too convenient”, I’m afraid this would give an
> incentive to not check OpenPGP signatures when they are available.

Sorry, I have no idea what it means :-(

>> At first I also thought about building a package source and then to
>> calculate the hash of the store file, but this way will lead to the
>> wrong hashes for "snippet"-ed origins.  Or do I miss anything?
>
> Well, I think bindings for ‘package-source-derivation’ would also be
> useful, but IIUC this is not what you had in mind.

If you mean to make a command to build the current package source, it
can be done, although I don't see how it can be useful.

-- 
Alex