Re: [package-vc] Consider cleaning up files from install process

[Philip Kaludercic]

Adam Porter <adam@alphapapa.net> writes:

> On 9/19/23 08:50, Philip Kaludercic wrote:
>
>>> An alternative would be to follow Quelpa's example: rather than
>>> loading the package directly from the git repository's directory, the
>>> package's files could be copied into a new directory in the elpa/
>>> directory, and Emacs could load the package from there.
>>>
>>> As a developer, I would prefer that approach, because I don't usually
>>> want Emacs to load whatever commit I may have checked out in a
>>> package's repository.  I want to install a commit of a package into my
>>> Emacs configuration and have that one loaded until I install a
>>> different one.
>> Isn't this workflow already supported by `package-install-file'?
>> And
>> otherwise, there wouldn't be much of a point to just replicate the
>> functionality of an existing package manager.
>
> That doesn't seem to do the same thing: it doesn't install from a git
> repo, per se, but from local files or directories:
>
>   (package-install-file FILE)
>
>   Install a package from FILE.
>   The file can either be a tar file, an Emacs Lisp file, or a
>   directory.
>
> What I like to do is to install the package from the git repo as a,
> well, "normal package," i.e. as if it were installed from ELPA.
> That's how Quelpa works: it produces,
> e.g. "~/.emacs.d/elpa/PACKAGE-VERSION/PACKAGE{,...}.el".  I don't have
> to have a local clone of the repo first.
>
> (Also, the name of the command suggests that it only installs from
> files rather than directories; I didn't even realize it could install
> from directories until now.)
>
>>> In other words, the way package-vc-install currently works leaves me
>>> vulnerable to this scenario:
>>>
>>> 1.  I use package-vc-install to install one of my packages from its
>>> local repository directory.
>>> 2.  I check out a feature branch of that package to work on a new
>>> feature, saving some files but not loading any of the changed code.
>>> 3.  I restart Emacs (e.g. maybe I shut down the system and turned it
>>> back on the next day).
>>> 4.  That work-in-progress feature branch of my package gets loaded
>>> into Emacs automatically (which may be entirely broken, being a WIP).
>> I understand your issue, but anecdotally, I can also give an example
>> where I wanted to change some functionality, by M-x find-function'ing
>> the source buffer and then loosing the change after upgrading the
>> package.
>
> IMHO that seems like a sort of user-error, to leave uncommitted
> changes in a repo that's under the control of a system that doesn't
> take such changes into account when operating on the repo.  IOW, if I
> install a package with command package-FOO, I expect the files it
> makes to be under its purview, not mine; they are not my personal data
> files, but belong to Emacs and its package.el library, the same as if
> I used "M-x package-install".

I don't believe in these kinds of distinctions.  I can change what I
want, the only question I have to keep in mind is what the chances of
loosing these changes is going to be.

> To put it another way, it seems like a bit of an anti-pattern to
> develop a package that's stored in "~/.emacs.d/elpa"--that directory
> is supposed to be for installed packages' files, and it should be safe
> to wipe that directory out at any time and reinstall packages from
> their sources--after all, 

Is that documented anywhere?  I know it can be done, if your
configuration is written accordingly, but if you see installed packages
as not being part of your domain, then transgressing layers of
abstraction and accessing, then deleting the "internal" representation
of package.el would seem to also be wrong?

>                           "M-x package-delete" shouldn't be wiping out
> user data.  Development on packages should be done on clones stored
> outside of "~/.emacs.d", e.g. in "~/src" or whatever one uses.  IMHO,
> of course--Emacs is all about user freedom--yet I think we should
> encourage the better practices.

I don't see it that way, but the technical background for this decision
is that source packages -- written with the intention of loading the
source code directly from the checkout -- should be loadable without
having to require package-vc, since package-vc is just an extension of
package.el that allows for an alternative way of installing packages.

>>> Whereas if I use Quelpa, it installs the files a package's recipe
>>> specifies into the expected location in the elpa/ directory, and that
>>> remains independent of whatever I may have checked out in the
>>> package's local git directory.  My Emacs configuration and installed
>>> packages remain consistent regardless of whatever in-between state I
>>> may have left a package's repository in.
>>>
>>> Philip, would you be willing to consider switching to that model for
>>> package-vc-install, or offering it as an option?
>> Can you describe the interface you are imagining.  From what I
>> understand, it should be possible to reproduce what you need by
>> combining `package-vc-checkout' and `package-install-file'?
>
> Well, I would expect it to act similarly to Quelpa:
>
> 1. Clone the git repo (shallowly, at least by default) to a directory
> (perhaps a temporary one, but at least one stored in the appropriate
> XDG cache directory, outside of user-emacs-directory).
>
> 2.  Call package-install-file on that worktree.
>
> 3.  The package ends up installed into package-user-dir as if it were
> installed with package-install from ELPA.

How does this look like:

--8<---------------cut here---------------start------------->8---
(defun package-vc-install-copy (pkg-desc)
  "Fetch the package sources of PKG-DESC and install a copy."
  (interactive (list (package-vc--read-package-desc "Fetch package source: ")))
  (let* ((copy (copy-package-desc pkg-desc))
         (package-dir (expand-file-name
                       (symbol-name (package-desc-name pkg-desc))
                       (make-temp-file "package-vc-" t)))
         (package-vc-register-as-project nil))
    (setf (package-desc-dir copy) package-dir)
    (save-window-excursion
      (package-vc-checkout pkg-desc package-dir)
      (package-install-from-buffer))))
--8<---------------cut here---------------end--------------->8---

I'd ideally pass :last-release to package-vc-checkout, but I have
detected a bug with this setup that should be fixed.

> Then if the user wants to modify the package, he should either a) use
> a local clone wherever he keeps such projects, or b) configure
> package-vc to clone the repo to such a directory, and then a command
> could automate finding the source files in that directory rather than
> the ones in package-user-dir which are loaded into Emacs.  (IIRC
> Straight, for example, does something like this, but I don't use it
> myself.)

To my understanding Straight maintains all packages in separate
repositories, then symlinks the files that are to be loaded.  So just
like with package-vc, you always have direct access to the source code
under VC.

> Do these explanations clarify what I mean?  Let me know if I need to
> try again.  :)

The main question I have is what advantage or disadvantage this would
provide over Quelpa?  The functionality you describe misses the point of
what I see to be the point of package-vc, as it wasn't written to be a
replacement of Straight or Quelpa (I have never used either of the two),
but just as a tool to streamline fetching and preparing packages
directly from source code repositories.

> --Adam