From 9b980e2691afa3a7a967011fc004d352750fe618 Mon Sep 17 00:00:00 2001
From: Eric Abrahamsen <eric@ericabrahamsen.net>
Date: Tue, 12 Sep 2017 16:06:12 -0700
Subject: [PATCH] Allow write-contents-functions to short-circuit buffer save
Bug#28412
* lisp/files.el (basic-save-buffer): Re-arrange function so that
write-contents-functions are run earlier. If they return non-nil,
consider the buffer saved without requiring the buffer to be
visiting a file.
(save-some-buffers): This function should consider any buffer with a
buffer-local value for write-contents-functions eligible for
saving.
* test/lisp/files-tests.el (files-test-no-file-write-contents): New
test.
* doc/lispref/files.texi (Saving Buffers): Mention in docs.
* etc/NEWS: And in NEWS.
---
doc/lispref/files.texi | 18 ++++--
etc/NEWS | 8 +++
lisp/files.el | 136 +++++++++++++++++++++------------------
test/lisp/files-tests.el | 27 ++++++++
4 files changed, 122 insertions(+), 67 deletions(-)
diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index 901382fe9bd..6be998f0b2e 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -457,15 +457,23 @@ Even though this is not a normal hook, you can use @code{add-hook} and
@defvar write-contents-functions
This works just like @code{write-file-functions}, but it is intended
for hooks that pertain to the buffer's contents, not to the particular
-visited file or its location. Such hooks are usually set up by major
-modes, as buffer-local bindings for this variable. This variable
-automatically becomes buffer-local whenever it is set; switching to a
-new major mode always resets this variable, but calling
-@code{set-visited-file-name} does not.
+visited file or its location, and can be used to create arbitrary save
+processes for buffers that aren't visiting files at all. Such hooks
+are usually set up by major modes, as buffer-local bindings for this
+variable. This variable automatically becomes buffer-local whenever
+it is set; switching to a new major mode always resets this variable,
+but calling @code{set-visited-file-name} does not.
If any of the functions in this hook returns non-@code{nil}, the file
is considered already written and the rest are not called and neither
are the functions in @code{write-file-functions}.
+
+When using this hook to save buffers that are not visiting files (for
+instance, special-mode buffers), keep in mind that, if the function
+fails to save correctly and returns a @code{nil} value,
+@code{save-buffer} will go on to prompt the user for a file to save
+the buffer in. If this is undesirable, consider having the function
+fail by raising an error.
@end defvar
@defopt before-save-hook
diff --git a/etc/NEWS b/etc/NEWS
index 03ef05b2a30..94673697090 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -108,6 +108,14 @@ The effect is similar to that of "toolBar" resource on the tool bar.
* Changes in Emacs 26.1
++++
+** Functions in 'write-contents-functions' can fully short-circuit the
+'save-buffer' process. Previously, saving a buffer that was not
+visiting a file would always prompt for a file name. Now it only does
+so if 'write-contents-functions' is nil (or all its functions return
+nil). A non-nil buffer-local value for this variable is sufficient
+for 'save-some-buffers' to consider the buffer for saving.
+
---
** New variable 'executable-prefix-env' for inserting magic signatures.
This variable affects the format of the interpreter magic number
diff --git a/lisp/files.el b/lisp/files.el
index de9fab8d32e..72ace246445 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -517,10 +517,12 @@ updates before the buffer is saved, use `before-save-hook'.")
'write-contents-functions "22.1")
(defvar write-contents-functions nil
"List of functions to be called before writing out a buffer to a file.
-Only used by `save-buffer'.
-If one of them returns non-nil, the file is considered already written
-and the rest are not called and neither are the functions in
-`write-file-functions'.
+
+Only used by `save-buffer'. If one of them returns non-nil, the
+file is considered already written and the rest are not called
+and neither are the functions in `write-file-functions'. This
+hook can thus be used to create save behavior for buffers that
+are not visiting a file at all.
This variable is meant to be used for hooks that pertain to the
buffer's contents, not to the particular visited file; thus,
@@ -4875,9 +4877,12 @@ in such cases.")
(defun basic-save-buffer (&optional called-interactively)
"Save the current buffer in its visited file, if it has been modified.
-The hooks `write-contents-functions' and `write-file-functions' get a chance
-to do the job of saving; if they do not, then the buffer is saved in
-the visited file in the usual way.
+
+The hooks `write-contents-functions', `local-write-file-hooks'
+and `write-file-functions' get a chance to do the job of saving;
+if they do not, then the buffer is saved in the visited file in
+the usual way.
+
Before and after saving the buffer, this function runs
`before-save-hook' and `after-save-hook', respectively."
(interactive '(called-interactively))
@@ -4886,29 +4891,14 @@ Before and after saving the buffer, this function runs
(if (buffer-base-buffer)
(set-buffer (buffer-base-buffer)))
(if (or (buffer-modified-p)
- ;; handle the case when no modification has been made but
- ;; the file disappeared since visited
+ ;; Handle the case when no modification has been made but
+ ;; the file disappeared since visited.
(and buffer-file-name
(not (file-exists-p buffer-file-name))))
(let ((recent-save (recent-auto-save-p))
setmodes)
- ;; If buffer has no file name, ask user for one.
- (or buffer-file-name
- (let ((filename
- (expand-file-name
- (read-file-name "File to save in: "
- nil (expand-file-name (buffer-name))))))
- (if (file-exists-p filename)
- (if (file-directory-p filename)
- ;; Signal an error if the user specified the name of an
- ;; existing directory.
- (error "%s is a directory" filename)
- (unless (y-or-n-p (format-message
- "File `%s' exists; overwrite? "
- filename))
- (error "Canceled"))))
- (set-visited-file-name filename)))
- (or (verify-visited-file-modtime (current-buffer))
+ (or (null buffer-file-name)
+ (verify-visited-file-modtime (current-buffer))
(not (file-exists-p buffer-file-name))
(yes-or-no-p
(format
@@ -4920,6 +4910,7 @@ Before and after saving the buffer, this function runs
(save-excursion
(and (> (point-max) (point-min))
(not find-file-literally)
+ (null buffer-read-only)
(/= (char-after (1- (point-max))) ?\n)
(not (and (eq selective-display t)
(= (char-after (1- (point-max))) ?\r)))
@@ -4932,46 +4923,65 @@ Before and after saving the buffer, this function runs
(save-excursion
(goto-char (point-max))
(insert ?\n))))
- ;; Support VC version backups.
- (vc-before-save)
;; Don't let errors prevent saving the buffer.
(with-demoted-errors (run-hooks 'before-save-hook))
- (or (run-hook-with-args-until-success 'write-contents-functions)
- (run-hook-with-args-until-success 'local-write-file-hooks)
- (run-hook-with-args-until-success 'write-file-functions)
- ;; If a hook returned t, file is already "written".
- ;; Otherwise, write it the usual way now.
- (let ((dir (file-name-directory
- (expand-file-name buffer-file-name))))
- (unless (file-exists-p dir)
- (if (y-or-n-p
- (format-message
- "Directory `%s' does not exist; create? " dir))
- (make-directory dir t)
- (error "Canceled")))
- (setq setmodes (basic-save-buffer-1))))
+ ;; Give `write-contents-functions' a chance to
+ ;; short-circuit the whole process.
+ (unless (run-hook-with-args-until-success 'write-contents-functions)
+ ;; If buffer has no file name, ask user for one.
+ (or buffer-file-name
+ (let ((filename
+ (expand-file-name
+ (read-file-name "File to save in: "
+ nil (expand-file-name (buffer-name))))))
+ (if (file-exists-p filename)
+ (if (file-directory-p filename)
+ ;; Signal an error if the user specified the name of an
+ ;; existing directory.
+ (error "%s is a directory" filename)
+ (unless (y-or-n-p (format-message
+ "File `%s' exists; overwrite? "
+ filename))
+ (error "Canceled"))))
+ (set-visited-file-name filename)))
+ ;; Support VC version backups.
+ (vc-before-save)
+ (or (run-hook-with-args-until-success 'local-write-file-hooks)
+ (run-hook-with-args-until-success 'write-file-functions)
+ ;; If a hook returned t, file is already "written".
+ ;; Otherwise, write it the usual way now.
+ (let ((dir (file-name-directory
+ (expand-file-name buffer-file-name))))
+ (unless (file-exists-p dir)
+ (if (y-or-n-p
+ (format-message
+ "Directory `%s' does not exist; create? " dir))
+ (make-directory dir t)
+ (error "Canceled")))
+ (setq setmodes (basic-save-buffer-1)))))
;; Now we have saved the current buffer. Let's make sure
;; that buffer-file-coding-system is fixed to what
;; actually used for saving by binding it locally.
- (if save-buffer-coding-system
- (setq save-buffer-coding-system last-coding-system-used)
- (setq buffer-file-coding-system last-coding-system-used))
- (setq buffer-file-number
- (nthcdr 10 (file-attributes buffer-file-name)))
- (if setmodes
- (condition-case ()
- (progn
- (unless
- (with-demoted-errors
- (set-file-modes buffer-file-name (car setmodes)))
- (set-file-extended-attributes buffer-file-name
- (nth 1 setmodes))))
- (error nil))))
- ;; If the auto-save file was recent before this command,
- ;; delete it now.
- (delete-auto-save-file-if-necessary recent-save)
- ;; Support VC `implicit' locking.
- (vc-after-save)
+ (when buffer-file-name
+ (if save-buffer-coding-system
+ (setq save-buffer-coding-system last-coding-system-used)
+ (setq buffer-file-coding-system last-coding-system-used))
+ (setq buffer-file-number
+ (nthcdr 10 (file-attributes buffer-file-name)))
+ (if setmodes
+ (condition-case ()
+ (progn
+ (unless
+ (with-demoted-errors
+ (set-file-modes buffer-file-name (car setmodes)))
+ (set-file-extended-attributes buffer-file-name
+ (nth 1 setmodes))))
+ (error nil)))
+ ;; Support VC `implicit' locking.
+ (vc-after-save))
+ ;; If the auto-save file was recent before this command,
+ ;; delete it now.
+ (delete-auto-save-file-if-necessary recent-save))
(run-hooks 'after-save-hook))
(or noninteractive
(not called-interactively)
@@ -5183,7 +5193,9 @@ change the additional actions you can take on files."
(and pred
(progn
(set-buffer buffer)
- (and buffer-offer-save (> (buffer-size) 0)))))
+ (and buffer-offer-save (> (buffer-size) 0))))
+ (buffer-local-value
+ 'write-contents-functions buffer))
(or (not (functionp pred))
(with-current-buffer buffer (funcall pred)))
(if arg
diff --git a/test/lisp/files-tests.el b/test/lisp/files-tests.el
index b52965a02b4..c6806cdb58e 100644
--- a/test/lisp/files-tests.el
+++ b/test/lisp/files-tests.el
@@ -365,6 +365,33 @@ be invoked with the right arguments."
(should-error (make-directory a/b))
(should-not (make-directory a/b t))))
+(ert-deftest files-test-no-file-write-contents ()
+ "Test that `write-contents-functions' permits saving a file.
+Usually `basic-save-buffer' will prompt for a file name if the
+current buffer has none. It should first call the functions in
+`write-contents-functions', and if one of them returns non-nil,
+consider the buffer saved, without prompting for a file
+name (Bug#28412)."
+ (let ((read-file-name-function
+ (lambda (&rest _ignore)
+ (error "Prompting for file name"))))
+ ;; With contents function, and no file.
+ (with-temp-buffer
+ (setq write-contents-functions (lambda () t))
+ (set-buffer-modified-p t)
+ (should (null (save-buffer))))
+ ;; With no contents function and no file. This should reach the
+ ;; `read-file-name' prompt.
+ (with-temp-buffer
+ (set-buffer-modified-p t)
+ (should-error (save-buffer) :type 'error))
+ ;; Then a buffer visiting a file: should save normally.
+ (files-tests--with-temp-file temp-file-name
+ (with-current-buffer (find-file-noselect temp-file-name)
+ (setq write-contents-functions nil)
+ (insert "p")
+ (should (null (save-buffer)))
+ (should (eq (buffer-size) 1))))))
(provide 'files-tests)
;;; files-tests.el ends here
--
2.39.5