Re: master 5183123: Add Tramp recompilation

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

>> I think we should treat this is a bug in package.el: we already have
>> code to try and avoid such problems, so apparently it doesn't do its job
>> in this case.
> The point is that simply unloading Tramp didn't work.

The way package.el tries to deal with it currently is not by unloading
the package (which we consider as too risky) but by force-loading the
new files over the old ones.  E.g. we load ~/.emacs.d/elpa/.../tramp-compat.el
before starting the compilation if we see that `tramp-compat` is in the
load-history.

I recommend you open a bug report for the current problem, and we can
try and figure out what's the root cause of the miscompilation.
That will help us figure out how to better avoid such problems.

> That's why I start a new Emacs instance via "emacs -Q" for
> recompilation. Maybe we could use this approach in package.el?

The `async` package provides such a solution indeed.  It'd be good to
integrate it into Emacs proper.

> I'll happily remove tramp-recompile-elpa from Tramp once recompilation
> is fixed in package.el. But since Tramp is backwards compatible (down to
> Emacs 25.1 ATM), this will take years.

I'm not bothered by the existence of `tramp-recompile-elpa` (interactive
or not).  I just saw that "a lot of effort" was expanded trying to make
it work smoothly whereas I thought we should spend more time making
it unnecessary.

>>>> [ Also, I don't see why we need `tramp-recompile-elpa`.
>>>>   I do see a need for `M-x package-recompile`, OTOH.  ]
>>> D'accord.
>> Patches warmly welcome,
> I'll have a look at it. No promise for a working patch, of course.

If you take the first step, I can probably help take the second.


        Stefan