Re: org-assert-version considered harmful

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

Ihor Radchenko [2023-08-16 11:08:15] wrote:
> Ihor Radchenko <yantar92@posteo.net> writes:
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>> BTW, rather than unloading, `package.el` relies on forcibly "re"loading
>>> from the new version the already loaded files from the old version.
>>> It suffers from a different set of problem :-(
>>> [ I suspect `defvar` is the main problem for that solution.  ]
>>
>> Could it be possible to force require use certain package version and
>> automatically re-load a package when older version is being loaded?
>
> After trying several more approaches,

[ Side note: did you keep notes about the various approaches you tried
  and their respective downsides?  E.g. I'm curious what were the
  problems linked to my proposal of using a `require-with-check` like
  the one below my sig.  ]

> I now came up with yet another idea.  Instead of fiddling with load
> internals, compilation, or load-path, what about making sure that Org
> libraries include version info directly?

That should work.  It implies a fair bit more churn in the code, tho,
but I guess you plan to automate it via some scripts?


        Stefan


(defun require-with-check (feature &optional filename noerror)
  "If FEATURE is not already loaded, load it from FILENAME.
This is like `require' except if FEATURE is already a member of the list
‘features’, then we check if this was provided by a different file than the
one that we would load now (presumably because `load-path' has been
changed since the file was loaded)."
  (let ((lh load-history)
        (res (require feature filename noerror)))
    ;; If the `feature' was not yet provided, `require' just loaded the right
    ;; file, so we're done.
    (if (not (eq lh load-history)) res
      ;; If `require' did nothing, we need to make sure that was warranted.
      (let ((fn (locate-file (or filename (symbol-name feature))
                             load-path (get-load-suffixes))))
        ;; If the right file was indeed loaded already, we're done.
        (if (assoc fn load-history) res
          (funcall (if noerror #'warn #'error)
                   "Feature provided by other file: %S" feature)
          res)))))