The Tower Of BABYL


I’ve finally found the proof of file-local variables being a hack: Every non-interactive function and variable dealing with them uses hack- as prefix! hack-local-variables does the heavy lifting, hack-local-variables-confirm nags you into acknowledging the potential dangers of such variables, etc.

Does the same hold true for directory-local variables? I’m pretty sure of it, given the existence of the following:

;; This is an odd variable IMO.
;; You might wonder why it is needed, when we could just do:
;; (set (make-local-variable 'enable-local-variables) nil)
;; These two are not precisely the same.
;; Setting this variable does not cause -*- mode settings to be
;; ignored, whereas setting enable-local-variables does.
;; Only three places in Emacs use this variable: tar and arc modes,
;; and rmail.  The first two don't need it.  They already use
;; inhibit-local-variables-regexps, which is probably enough, and
;; could also just set enable-local-variables locally to nil.
;; Them setting it has the side-effect that dir-locals cannot apply to
;; eg tar files (?).  FIXME Is this appropriate?
;; AFAICS, rmail is the only thing that needs this, and the only
;; reason it uses it is for BABYL files (which are obsolete).
;; These contain "-*- rmail -*-" in the first line, which rmail wants
;; to respect, so that find-file on a BABYL file will switch to
;; rmail-mode automatically (this is nice, but hardly essential,
;; since most people are used to explicitly running a command to
;; access their mail; M-x gnus etc).  Rmail files may happen to
;; contain Local Variables sections in messages, which Rmail wants to
;; ignore.  So AFAICS the only reason this variable exists is for a
;; minor convenience feature for handling of an obsolete Rmail file format.
(defvar local-enable-local-variables t
  "Like `enable-local-variables' but meant for buffer-local bindings.
The meaningful values are nil and non-nil.  The default is non-nil.
If a major mode sets this to nil, buffer-locally, then any local
variables list in a file visited in that mode will be ignored.

This variable does not affect the use of major modes specified
in a -*- line.")