bug#70136: 30.0.50; compilation-mode [was: comint-mode] doesn't call hack-dir-local-variables-non-file-buffer

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>> @@ -2372,6 +2363,11 @@ compilation-mode
>>    ;; some other input event happens.
>>    (setq-local jit-lock-defer-time nil)
>>    (setq buffer-read-only t)
>> +  (unless (buffer-file-name)
>> +    (let ((sym (make-symbol "hack-dir-local-variables-non-file-buffer")))
>> +      (set sym #'hack-dir-local-variables-non-file-buffer)
>> +      ;; Ensure hack-dir-locals is called only after a derived mode is set.
>> +      (push sym delayed-mode-hooks)))
>>    (run-mode-hooks 'compilation-mode-hook))
>
> Thanks for the patch.  I confirm it completely fixes the bug
> reported at the end of bug#68570.

Clearly, I'm in favor, tho I find the specific code above rather ugly.
Could we improve it?
Maybe setting a `enable-dir-local-variables-non-file-buffer` variable,
which is then obeyed in the hack-local-* functions?


        Stefan