bug#57003: 28.1.90; Can local variables be loaded before loading major mode?

[Visuwesh]

[சனி ஆகஸ்ட் 06, 2022] Ihor Radchenko wrote:

> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
>> Is the problem here that there are defvars in the major-mode file being
>> loaded that depend on one another?  (I'm not sure I understand the
>> explanation in that bug report.)
>
> No.
>
> Let me try to explain a simple case when setting variables before/after
> loading Org mode matters.
>
> We have a variable org-startup-folded:
>
>    Non-nil means entering Org mode will switch to OVERVIEW.
>
> This variable controls the initial state of the Org buffer.
> When, non-nil, headings will be folded at the end of Org initialization.
> This folding happens inside org-mode specification and hence setting the
> variable after Org mode is loaded makes no difference.
>
> There are also less trivial cases like some variables controlling Org
> parser. For example, we have org-todo-keywords. Its value controls how
> the headlines are parsed. Because Org parser is initialized during Org
> loading, setting this variable after loading Org mode can be simply
> disastrous.

Correct me if I'm wrong, this is about the major-mode definition
clearing the buffer's local variables before turning on the major-mode,
right?  If so, I was hit by this for a personal package too where I
needed to expose a local variable for the major-mode-hook but failed
because the function created `define-derived-mode' clears the buffer
local variables before running the major-mode-hook and the major-mode's
BODY.