Re: nadvice compatibility in package list

[Andy Moreton <andrewjmoreton@gmail.com>]

On Fri 05 Jul 2019, Stefan Monnier wrote:

>>   (assoc 'nadvice package--builtin-versions)
>>   => (nadvice 1 0)
>
> This is right.
>
>>   (assoc 'nadvice package--builtins)
>>   => nil
>
> This is wrong.
>
> Thomas Fitzsimmons <fitzsim@fitzsim.org> writes:
>> diff --git a/lisp/emacs-lisp/nadvice.el b/lisp/emacs-lisp/nadvice.el
>> index 2278e389ce..ffecb24b1a 100644
>> --- a/lisp/emacs-lisp/nadvice.el
>> +++ b/lisp/emacs-lisp/nadvice.el
>> @@ -3,8 +3,11 @@
>>  ;; Copyright (C) 2012-2019 Free Software Foundation, Inc.
>>  
>>  ;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
>> +;; Note: Always keep this built-in nadvice version greater than any
>> +;; nadvice version that has been or ever will be in GNU ELPA.
>> +;; Version: 10.0.0
>>  ;; Keywords: extensions, lisp, tools
>> -;; Package: emacs
>> +;; Package: nadvice
>>  
>>  ;; This program is free software; you can redistribute it and/or modify
>>  ;; it under the terms of the GNU General Public License as published by
>
> We already have defined its version as 1.0, so it would be better to
> keep it that way.  I think the only thing that really matters is to
> remove the `Package: emacs` line (which is a line that explicitly
> *prevents* the file from being considered as a package in its own
> right).

The patch above works:

(assoc 'nadvice package--builtin-versions)
=> (nadvice 1 0)

(assoc 'nadvice package--builtins)
=> (nadvice . [(10 0 0) nil "Light-weight advice primitives for Elisp functions"])

The `list-packages' output shows two nadvice packages:
  nadvice                   0.3           available  gnu        Forward compatibility for Emacs-24.4's nadvice
  nadvice                   10.0.0        built-in              Light-weight advice primitives for Elisp functions

> So I think the patch below will do the trick as well.
> Can you confirm?

Stefan, your patch gives the right assoc lookups, but does not show the
builtin nadvice package in the output from `list-packages'.

In general, omitting the "Package:" directive is a little too subtle,
and future maintainers may add it back, assuming it was an unintended
omission rather than a deliberate change.

To test each patch I deleted lisp/finder-inf.el before rebuilding. Let
me know if this is insufficient for a correct rebuild.

    AndyM