bug#62720: 29.0.60; Not easy at all to upgrade :core packages like Eglot

[Eli Zaretskii]

> From: Philip Kaludercic <philipk@posteo.net>
> Cc: joaotavora@gmail.com,  monnier@iro.umontreal.ca,  62720@debbugs.gnu.org,
>   larsi@gnus.org
> Date: Thu, 13 Apr 2023 11:23:12 +0000
> 
> > Why did the original code use symbol-name, but the new one doesn't?
> 
> To my knowledge, completing-read given a collection of symbols will use
> the symbol names as candidates, or is this more complicated?

So you are saying that the symbol-name call in the original code was
simply redundant?

> >> @@ -2221,11 +2236,16 @@ package-install
> >>        (package--save-selected-packages
> >>         (cons name package-selected-packages)))
> >>      (if-let* ((transaction
> >> -               (if (package-desc-p pkg)
> >> -                   (unless (package-installed-p pkg)
> >> -                     (package-compute-transaction (list pkg)
> >> -                                                  (package-desc-reqs 
> >> pkg)))
> >> -                 (package-compute-transaction () (list (list pkg))))))
> >> +               (cond
> >> +                ((package--upgradable-built-in-p pkg)
> >> +                 (let ((desc (cadr (assq name package-archive-contents))))
> >> +                   (package-compute-transaction
> >> +                    (list desc) (package-desc-reqs desc))))
> >> +                ((package-desc-p pkg)
> >> +                 (and (not (package-installed-p pkg))
> >> +                      (package-compute-transaction
> >> +                       (list pkg) (package-desc-reqs pkg))))
> >> +                ((package-compute-transaction () (list (list pkg)))))))
> >
> > I think the first condition of 'cond' should be
> >
> >     ((and current-prefix-arg (package--upgradable-built-in-p pkg))
> >
> > to make sure we don't affect the non-prefix-arg invocations in any
> > way.
> 
> The issue here is that this breaks the non-interactive invocations like
> (package-install 'eglot), unless they invoke the function while binding
> `current-prefix-arg', which I don't think is a common practice.

Then let's add another optional argument, and let prefix arg set it.
Would that resolve this issue?

> >> Note that (package-install 'eglot) does download code, but I believe
> >> that this is the correct approach and would align with what João
> >> wanted.
> >
> > I'm not sure I follow: which code does the above download?
> 
> I did not change any of the code that downloads anything, all this does
> is prompt the user for built-in packages when invoked interactively with
> a prefix argument and if package-install is invoked with a built-in
> package, then it will switch to the ELPA version.  This will not happen
> in interactive usage, since `completing-read' is called with
> REQUIRE-MATCH.

So you are saying that non-interactive calls to package-install could
install Eglot from ELPA even without the changes, is that right?