Re: Automatically saving package sources

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> It is nice for installed ELPA packages to be reinstalled when Emacs is
>> upgraded or changed, since there can be changes to autoload generation,
>> the byte compiler, the native compiler, or other things which will
>> change the output from the package installation.

FWIW, native-compiled files do get regenerated (and from the `.el`
rather than from the `.elc`).  So the problem is more for autoloads and
`.elc` files.  And we do have `package-recompile` since Emacs-29.1.

>> However, right now there is no easy way to reinstall a package from the
>> same sources it was originally installed from, because those sources are
>> not saved separately from the package itself.  They are all mixed
>> together in the installed package directory.  This makes it impossible
>> to produce a "clean slate" environment for reinstalling the package,
>> which (since packages can create arbitrary files during
>> byte-compilation) means the package can't be reinstalled in a way that's
>> identical to its original installation.

While that's true in theory, in practice `package-recompile` should work
fine for all but the "weirdest" packages.

>> I would like to add an option package-save-sources which makes
>> package.el automatically save the package source for the currently
>> installed package version in a separate directory.  Perhaps in
>> ~/.emacs.d/elpa-sources.

It could make sense to keep the tarballs, indeed.
I would see it as a cache: when asking to reinstall, we'd try and
re-fetch that specific package version, first looking for a local copy
in our cache, then looking for it in the repository ((Non)GNU ELPA does
keep a number of older versions, even though they're not listed in
`archive-contents`).
And if that fails, there's still `package-recompile` or an upgrade.


        Stefan