>>>>> Ikumi Keita <ikumi@ikumi.que.jp> writes:
> The point is that AUCTeX should extend this follow-up on
> `derived-mode-p' to `provided-mode-derived-p'. I'll explain the detail
> in a few days.

Here we go.
1. In my feature branch and current AUCTeX, I added pseudo-parent mode
   facility[1][2] like emacs 30 in order to have compatibility with
   directory local variable entry prepared for former mode names like
   `latex-mode'.

2. That facility only concerns for `derived-mode-p' and doesn't tweak
   `provided-mode-derived-p'. However, the `run-if' property of
   `text-colum' entry in `align-rules-list'[3] uses
   `provided-mode-derived-p'. This discrepancy calls for a spurious
   alignment is in `LaTeX-mode' because it isn't considered as derived
   from modes listed in `align-tex-modes'

3. This spurious alignment doen't occur in emacs 30 since it overhauls
   `provided-mode-derived-p' in depth.

4. The attached patch improves the pseudo-parent mode facility to cover
   `provided-mode-derived-p' as well, and fix this bug.

5. The entry `tex-tabbing-separator' in `align-rules-list'[4] has to be
   fixed because its `run-if' property contains conditional with repect
   to the major mode without `derived-mode-p' nor
   `provided-mode-derived-p'. I'll file a bug report for this.

[1] `TeX-derived-mode-add-parents'
[2] advice for `derived-mode-p' by `TeX--compat-derived-mode-p'
[3]-------------------------------------------------------------------
    ;; Align space delimited text as columns.
    (text-column
     (regexp   . "\\(^\\|\\S-\\)\\([ \t]+\\)\\(\\S-\\|$\\)")
     (group    . 2)
     (modes    . align-text-modes)
     (repeat   . t)
     (run-if   . ,(lambda ()
                    (and (not (eq '- current-prefix-arg))
                         (not (apply #'provided-mode-derived-p
                                     major-mode align-tex-modes))))))
----------------------------------------------------------------------
[4]-------------------------------------------------------------------
    (tex-tabbing-separator
     (regexp   . ,(lambda (end reverse)
                    (align-match-tex-pattern "\\\\[=>]" end reverse)))
     (group    . (1 2))
     (modes    . align-tex-modes)
     (repeat   . t)
     (run-if   . ,(lambda ()
                    (eq major-mode 'latex-mode))))
----------------------------------------------------------------------

Regards,
Ikumi Keita
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