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Call hack-local-variables from major modes rather than from file visiting

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This prevents file/directory local variables from being lost when the major
mode is set or changed.

This fixes bug #15577 and bug #23407.

* lisp/files.el (normal-mode): Call `hack-local-variables' when the major mode
function hasn't already done so.
(hack-local-variables): Rename parameter `mode-only' to `handle-mode', make
its previous non-nil setting be t, and introduce the following action for a
non-nil non-t value: apply all settings apart from `mode'.

* lisp/subr.el (run-mode-hooks): call `hack-local-variables' for buffers
which are visiting files.

* doc/emacs/custom.texi (File Variables): Note that setting a major mode also
sets file variables.
(Directory Variables): Note that `mode', `eval', and `unibyte' can be set as
dir local variables, but `coding' can't.

* doc/lispref/modes.texi (Major Mode Conventions): Say that `run-mode-hooks'
also calls `hack-local-variables'.
(Auto Major Mode): Say that `find-file' no longer runs `hack-local-variables',
as from 25.2.  Remove vagueness from `normal-mode' and `set-auto-mode' by
saying that the mode IS SET, not merely "selected" or "chosen".
(Mode Hooks): Document change to `run-mode-hooks'.

* doc/lispref/variables.texi (File Local Variables): Document change to
`hack-local-variables'.
This commit is contained in:
Alan Mackenzie 2016-05-05 11:05:49 +00:00
parent 6aad36ace9
commit 25f455815b
5 changed files with 81 additions and 49 deletions
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13
doc/emacs/custom.texi
View file

@ -1037,9 +1037,10 @@ explicitly. For example, here's how to obtain the default value of
@cindex file local variables
A file can specify local variable values to use when editing the
file with Emacs. Visiting the file checks for local variable
specifications; it automatically makes these variables local to the
buffer, and sets them to the values specified in the file.
file with Emacs. Visiting the file or setting a major mode checks for
local variable specifications; it automatically makes these variables
local to the buffer, and sets them to the values specified in the
file.
@menu
* Specifying File Variables:: Specifying file local variables.
@ -1344,6 +1345,12 @@ be applied in the current directory, not in any subdirectories.
Finally, it specifies a different @file{ChangeLog} file name for any
file in the @file{src/imported} subdirectory.
You can specify the variables @code{mode}, @code{eval}, and
@code{unibyte} in your @file{.dir-locals.el}, and they have the same
meanings as they would have in file local variables. @code{coding}
cannot be specified as a directory local variable. @xref{File
Variables}.
@findex add-dir-local-variable
@findex delete-dir-local-variable
@findex copy-file-locals-to-dir-locals

52
doc/lispref/modes.texi
View file

@ -445,7 +445,8 @@ other packages would interfere with them.
Each major mode should have a normal @dfn{mode hook} named
@code{@var{modename}-mode-hook}. The very last thing the major mode command
should do is to call @code{run-mode-hooks}. This runs the normal
hook @code{change-major-mode-after-body-hook}, the mode hook,
hook @code{change-major-mode-after-body-hook}, the mode hook, the
function @code{hack-local-variables} (when the buffer is visiting a file),
and then the normal hook @code{after-change-major-mode-hook}.
@xref{Mode Hooks}.
@ -525,11 +526,12 @@ the buffer based on information in the file name or in the file itself.
It also processes local variables specified in the file text.
@deffn Command normal-mode &optional find-file
This function establishes the proper major mode and buffer-local variable
bindings for the current buffer. First it calls @code{set-auto-mode}
(see below), then it runs @code{hack-local-variables} to parse, and
bind or evaluate as appropriate, the file's local variables
(@pxref{File Local Variables}).
This function establishes the proper major mode and buffer-local
variable bindings for the current buffer. It calls
@code{set-auto-mode} (see below). As from Emacs 25.2, it no longer
runs @code{hack-local-variables}, this now being done in
@code{run-mode-hooks} at the initialization of major modes
(@pxref{Mode Hooks}).
If the @var{find-file} argument to @code{normal-mode} is non-@code{nil},
@code{normal-mode} assumes that the @code{find-file} function is calling
@ -543,9 +545,9 @@ If you run @code{normal-mode} interactively, the argument
@var{find-file} is normally @code{nil}. In this case,
@code{normal-mode} unconditionally processes any file local variables.
The function calls @code{set-auto-mode} to choose a major mode. If this
does not specify a mode, the buffer stays in the major mode determined
by the default value of @code{major-mode} (see below).
The function calls @code{set-auto-mode} to choose and set a major
mode. If this does not specify a mode, the buffer stays in the major
mode determined by the default value of @code{major-mode} (see below).
@cindex file mode specification error
@code{normal-mode} uses @code{condition-case} around the call to the
@ -555,16 +557,17 @@ mode specification error}, followed by the original error message.
@defun set-auto-mode &optional keep-mode-if-same
@cindex visited file mode
This function selects the major mode that is appropriate for the
current buffer. It bases its decision (in order of precedence) on the
@w{@samp{-*-}} line, on any @samp{mode:} local variable near the end of
a file, on the @w{@samp{#!}} line (using @code{interpreter-mode-alist}),
on the text at the beginning of the buffer (using
@code{magic-mode-alist}), and finally on the visited file name (using
@code{auto-mode-alist}). @xref{Choosing Modes, , How Major Modes are
Chosen, emacs, The GNU Emacs Manual}. If @code{enable-local-variables}
is @code{nil}, @code{set-auto-mode} does not check the @w{@samp{-*-}}
line, or near the end of the file, for any mode tag.
This function selects and sets the major mode that is appropriate
for the current buffer. It bases its decision (in order of
precedence) on the @w{@samp{-*-}} line, on any @samp{mode:} local
variable near the end of a file, on the @w{@samp{#!}} line (using
@code{interpreter-mode-alist}), on the text at the beginning of the
buffer (using @code{magic-mode-alist}), and finally on the visited
file name (using @code{auto-mode-alist}). @xref{Choosing Modes, , How
Major Modes are Chosen, emacs, The GNU Emacs Manual}. If
@code{enable-local-variables} is @code{nil}, @code{set-auto-mode} does
not check the @w{@samp{-*-}} line, or near the end of the file, for
any mode tag.
@vindex inhibit-local-variables-regexps
There are some file types where it is not appropriate to scan the file
@ -907,13 +910,14 @@ use the following functions to handle these conventions automatically.
@defun run-mode-hooks &rest hookvars
Major modes should run their mode hook using this function. It is
similar to @code{run-hooks} (@pxref{Hooks}), but it also runs
@code{change-major-mode-after-body-hook} and
@code{after-change-major-mode-hook}.
@code{change-major-mode-after-body-hook}, @code{hack-local-variables}
(when the buffer is visiting a file) (@pxref{File Local Variables}),
and @code{after-change-major-mode-hook}.
When this function is called during the execution of a
@code{delay-mode-hooks} form, it does not run the hooks immediately.
Instead, it arranges for the next call to @code{run-mode-hooks} to run
them.
@code{delay-mode-hooks} form, it does not run the hooks or
@code{hack-local-variables} immediately. Instead, it arranges for the
next call to @code{run-mode-hooks} to run them.
@end defun
@defmac delay-mode-hooks body@dots{}

16
doc/lispref/variables.texi
View file

@ -1613,7 +1613,7 @@ any form of file-local variable. For examples of why you might want
to use this, @pxref{Auto Major Mode}.
@end defvar
@defun hack-local-variables &optional mode-only
@defun hack-local-variables &optional handle-mode
This function parses, and binds or evaluates as appropriate, any local
variables specified by the contents of the current buffer. The variable
@code{enable-local-variables} has its effect here. However, this
@ -1630,11 +1630,15 @@ is non-@code{nil}; it always calls the other hook. This
function ignores a @samp{mode} element if it specifies the same major
mode as the buffer already has.
If the optional argument @var{mode-only} is non-@code{nil}, then all
this function does is return a symbol specifying the major mode,
if the @w{@samp{-*-}} line or the local variables list specifies one,
and @code{nil} otherwise. It does not set the mode nor any other
file-local variable.
If the optional argument @var{handle-mode} is @code{t}, then all this
function does is return a symbol specifying the major mode, if the
@w{@samp{-*-}} line or the local variables list specifies one, and
@code{nil} otherwise. It does not set the mode or any other
file-local variable. If @var{handle-mode} has any value other than
@code{nil} or @code{t}, any settings of @samp{mode} in the
@w{@samp{-*-}} line or the local variables list are ignored, and the
other settings are applied. If @var{handle-mode} is @code{nil}, all
the file local variables are set.
@end defun
@defvar file-local-variables-alist

38
lisp/files.el
View file

@ -2322,8 +2322,12 @@ in that case, this function acts as if `enable-local-variables' were t."
;; s-a-m and h-l-v may parse the same regions, looking for "mode:".
(with-demoted-errors "File mode specification error: %s"
(set-auto-mode))
(with-demoted-errors "File local-variables error: %s"
(hack-local-variables)))
;; `delay-mode-hooks' being non-nil will have prevented the major
;; mode's call to `run-mode-hooks' from calling
;; `hack-local-variables'. In that case, call it now.
(when delay-mode-hooks
(with-demoted-errors "File local-variables error: %s"
(hack-local-variables 'no-mode))))
;; Turn font lock off and on, to make sure it takes account of
;; whatever file local variables are relevant to it.
(when (and font-lock-mode
@ -3297,11 +3301,15 @@ DIR-NAME is the name of the associated directory. Otherwise it is nil."
;; TODO? Warn once per file rather than once per session?
(defvar hack-local-variables--warned-lexical nil)
(defun hack-local-variables (&optional mode-only)
(defun hack-local-variables (&optional handle-mode)
"Parse and put into effect this buffer's local variables spec.
Uses `hack-local-variables-apply' to apply the variables.
If MODE-ONLY is non-nil, all we do is check whether a \"mode:\"
If HANDLE-MODE is nil, we apply all the specified local
variables. If HANDLE-MODE is neither nil nor t, we do the same,
except that any settings of `mode' are ignored.
If HANDLE-MODE is t, all we do is check whether a \"mode:\"
is specified, and return the corresponding mode symbol, or nil.
In this case, we try to ignore minor-modes, and only return a
major-mode.
@ -3319,7 +3327,7 @@ local variables, but directory-local variables may still be applied."
(let ((enable-local-variables
(and local-enable-local-variables enable-local-variables))
result)
(unless mode-only
(unless (eq handle-mode t)
(setq file-local-variables-alist nil)
(with-demoted-errors "Directory-local variables error: %s"
;; Note this is a no-op if enable-local-variables is nil.
@ -3327,18 +3335,19 @@ local variables, but directory-local variables may still be applied."
;; This entire function is basically a no-op if enable-local-variables
;; is nil. All it does is set file-local-variables-alist to nil.
(when enable-local-variables
;; This part used to ignore enable-local-variables when mode-only
;; was non-nil. That was inappropriate, eg consider the
;; This part used to ignore enable-local-variables when handle-mode
;; was t. That was inappropriate, eg consider the
;; (artificial) example of:
;; (setq local-enable-local-variables nil)
;; Open a file foo.txt that contains "mode: sh".
;; It correctly opens in text-mode.
;; M-x set-visited-file name foo.c, and it incorrectly stays in text-mode.
(unless (or (inhibit-local-variables-p)
;; If MODE-ONLY is non-nil, and the prop line specifies a
;; If HANDLE-MODE is t, and the prop line specifies a
;; mode, then we're done, and have no need to scan further.
(and (setq result (hack-local-variables-prop-line mode-only))
mode-only))
(and (setq result (hack-local-variables-prop-line
(eq handle-mode t)))
(eq handle-mode t)))
;; Look for "Local variables:" line in last page.
(save-excursion
(goto-char (point-max))
@ -3393,7 +3402,7 @@ local variables, but directory-local variables may still be applied."
(goto-char (point-min))
(while (not (or (eobp)
(and mode-only result)))
(and (eq handle-mode t) result)))
;; Find the variable name;
(unless (looking-at hack-local-variable-regexp)
(error "Malformed local variable line: %S"
@ -3410,7 +3419,7 @@ local variables, but directory-local variables may still be applied."
(forward-char 1)
(let ((read-circle nil))
(setq val (read (current-buffer))))
(if mode-only
(if (eq handle-mode t)
(and (eq var 'mode)
;; Specifying minor-modes via mode: is
;; deprecated, but try to reject them anyway.
@ -3432,6 +3441,7 @@ local variables, but directory-local variables may still be applied."
;; to use 'thisbuf's name in the
;; warning message.
(or (buffer-file-name thisbuf) ""))))))
((and (eq var 'mode) handle-mode))
(t
(ignore-errors
(push (cons (if (eq var 'eval)
@ -3440,8 +3450,8 @@ local variables, but directory-local variables may still be applied."
val) result))))))
(forward-line 1))))))))
;; Now we've read all the local variables.
;; If MODE-ONLY is non-nil, return whether the mode was specified.
(if mode-only result
;; If HANDLE-MODE is t, return whether the mode was specified.
(if (eq handle-mode t) result
;; Otherwise, set the variables.
(hack-local-variables-filter result nil)
(hack-local-variables-apply)))))

11
lisp/subr.el
View file

@ -1737,10 +1737,14 @@ if it is empty or a duplicate."
(defun run-mode-hooks (&rest hooks)
"Run mode hooks `delayed-mode-hooks' and HOOKS, or delay HOOKS.
If the variable `delay-mode-hooks' is non-nil, does not run any hooks,
Call `hack-local-variables' to set up file local and directory local
variables.
If the variable `delay-mode-hooks' is non-nil, does not do anything,
just adds the HOOKS to the list `delayed-mode-hooks'.
Otherwise, runs hooks in the sequence: `change-major-mode-after-body-hook',
`delayed-mode-hooks' (in reverse order), HOOKS, and finally
`delayed-mode-hooks' (in reverse order), HOOKS, then runs
`hack-local-variables' and finally runs the hook
`after-change-major-mode-hook'. Major mode functions should use
this instead of `run-hooks' when running their FOO-mode-hook."
(if delay-mode-hooks
@ -1751,6 +1755,9 @@ this instead of `run-hooks' when running their FOO-mode-hook."
(setq hooks (nconc (nreverse delayed-mode-hooks) hooks))
(setq delayed-mode-hooks nil)
(apply 'run-hooks (cons 'change-major-mode-after-body-hook hooks))
(if (buffer-file-name)
(with-demoted-errors "File local-variables error: %s"
(hack-local-variables 'no-mode)))
(run-hooks 'after-change-major-mode-hook)))
(defmacro delay-mode-hooks (&rest body)