Bug? org-assert-version does not prevent mixed install

[Max Nikulin]

Hi,

It seems `org-assert-version' guard is not enough to protect against 
mixed install. Some code is required to generate a *fatal* error during 
compilation and a more descriptive error during loading.

I decided to look closer at
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=59882
"30.0.50; Compilation of ELPA packages during version upgrade (Org 9.6 
ELPA upgrade from older ELPA version)"
since the bug lacks explicit and clear steps to reproduce.

Let's leave that bug for emacs' stuff and concentrate on Org code here.

I have tried the following:
- Emacs-27.1 from Ubuntu-22.04 LTS jammy (elpa-org-9.5.2 is not 
important). I suppose emacs version should be less than 29.0 to avoid 
built-in Org version having `org-assert-version'.
- Since emacs does not allow to specify just `user-emacs-directory' from 
command line I had to create a new user, so default configuration maybe 
slightly modified by debian-specific stuff.
- "emacs -l org" to ensure that Org is loaded. "-q" or "-Q" are 
intentionally avoided to allow initialization and saving of modification 
as for normal emacs session.
- M-x list-packages, click org, click install
- I get some warnings
> Compiling file /home/emcs/.emacs.d/elpa/org-9.6/ob-C.el at Sun Dec 18 04:30:49 
> 2022
> Entering directory ‘/home/emcs/.emacs.d/elpa/org-9.6/’
>
> In end of data:
> ob-C.el:509:1:Warning: the function ‘org-assert-version’ is not known to be
>     defined.
and even errors. I have not idea why severity is different
> Compiling file /home/emcs/.emacs.d/elpa/org-9.6/ob-matlab.el at Sun Dec 18 
> 04:30:50 2022
> ob-matlab.el:43:1:Error: Symbol’s function definition is void: 
> org-assert-version
- org.elc is not created as well.
- Despite of warnings and errors the following added to ~/.emacs
> (custom-set-variables
>  '(package-selected-packages '(org htmlize)))
- next attempt to run "emacs -l org" causes the famous message
> byte-code: Invalid function: org-assert-version

Is it possible to signal a fatal error during installing using emacs 
machinery to prevent broken user configuration? My expectation that 
result of failed compilation is ignored by emacs.

It is possible to convert the error to a better one by checking if 
`org-assert-version' is bound in org.el.

I think, the following topics are more suitable for emacs bug tracker or 
devel mail list:
- how to compile packages to avoid issues with already loaded older 
packages,
- what changes are required in package management to roll back failed 
attempt of installing.