;;; filelock-tests.el --- test file locking -*- lexical-binding: t; -*-
;; Copyright (C) 2021-2024 Free Software Foundation, Inc.
;; This file is part of GNU Emacs.
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This file tests code in src/filelock.c and, to some extent, the
;; related code in src/fileio.c.
;;
;; See also (info "(emacs)Interlocking") and (info "(elisp)File Locks")
;;; Code:
(require 'cl-macs)
(require 'ert)
(require 'ert-x)
(require 'seq)
(defmacro filelock-tests--fixture (&rest body)
"Call BODY under a test fixture.
Create a test directory and a buffer whose `buffer-file-name' and
`buffer-file-truename' are a file within it, then call BODY.
Finally, delete the buffer and the test directory."
(declare (debug (body)))
`(ert-with-temp-directory temp-dir
(let ((name (concat (file-name-as-directory temp-dir)
"userfile"))
(create-lockfiles t))
(with-temp-buffer
(setq buffer-file-name name
buffer-file-truename name)
(unwind-protect
(save-current-buffer
,@body)
;; Set `buffer-file-truename' nil to prevent unlocking,
;; which might prompt the user and/or signal errors.
(setq buffer-file-name nil
buffer-file-truename nil))))))
(defun filelock-tests--make-lock-name (file-name)
"Return the lock file name for FILE-NAME.
Equivalent logic in Emacs proper is implemented in C and
unavailable to Lisp."
(concat (file-name-directory (expand-file-name file-name))
".#"
(file-name-nondirectory file-name)))
(defun filelock-tests--spoil-lock-file (file-name)
"Spoil the lock file for FILE-NAME.
Cause Emacs to report errors for various file locking operations
on FILE-NAME going forward. Create a file that is incompatible
with Emacs' file locking protocol, but uses the same name as
FILE-NAME's lock file. A directory file is used, which is
portable in practice."
(make-directory (filelock-tests--make-lock-name file-name)))
(defun filelock-tests--unspoil-lock-file (file-name)
"Remove the lock file spoiler for FILE-NAME.
See `filelock-tests--spoil-lock-file'."
(delete-directory (filelock-tests--make-lock-name file-name) t))
(defun filelock-tests--should-be-locked ()
"Abort the current test if the current buffer is not locked.
Exception: on systems without lock file support, aborts the
current test if the current file is locked (which should never
the case)."
(if (eq system-type 'ms-dos)
(should-not (file-locked-p buffer-file-truename))
(should (file-locked-p buffer-file-truename))))
(ert-deftest filelock-tests-lock-unlock-no-errors ()
"Check that locking and unlocking works without error."
(filelock-tests--fixture
(should-not (file-locked-p (buffer-file-name)))
;; Inserting text should lock the buffer's file.
(insert "this locks the buffer's file")
(filelock-tests--should-be-locked)
(unlock-buffer)
(set-buffer-modified-p nil)
(should-not (file-locked-p (buffer-file-name)))
;; `set-buffer-modified-p' should lock the buffer's file.
(set-buffer-modified-p t)
(filelock-tests--should-be-locked)
(unlock-buffer)
(should-not (file-locked-p (buffer-file-name)))
(should-not (file-locked-p (buffer-file-name)))))
(ert-deftest filelock-tests-lock-spoiled ()
"Check `lock-buffer'."
(skip-unless (not (eq system-type 'ms-dos))) ; no filelock support
(filelock-tests--fixture
(filelock-tests--spoil-lock-file buffer-file-truename)
;; FIXME: errors when locking a file are ignored; should they be?
(set-buffer-modified-p t)
(filelock-tests--unspoil-lock-file buffer-file-truename)
(should-not (file-locked-p buffer-file-truename))))
(ert-deftest filelock-tests-file-locked-p-spoiled ()
"Check that `file-locked-p' fails if the lockfile is \"spoiled\"."
(skip-unless (not (eq system-type 'ms-dos))) ; no filelock support
(filelock-tests--fixture
(filelock-tests--spoil-lock-file buffer-file-truename)
(let ((err (should-error (file-locked-p (buffer-file-name)))))
(should (equal (seq-subseq err 0 2)
(if (eq system-type 'windows-nt)
'(permission-denied "Testing file lock")
'(file-error "Testing file lock")))))))
(ert-deftest filelock-tests-unlock-spoiled ()
"Check that `unlock-buffer' fails if the lockfile is \"spoiled\"."
(skip-unless (not (eq system-type 'ms-dos))) ; no filelock support
(filelock-tests--fixture
;; Set the buffer modified with file locking temporarily disabled.
(let ((create-lockfiles nil))
(set-buffer-modified-p t))
(should-not (file-locked-p buffer-file-truename))
(filelock-tests--spoil-lock-file buffer-file-truename)
;; Errors from `unlock-buffer' should call
;; `userlock--handle-unlock-error' (bug#46397).
(cl-letf (((symbol-function 'userlock--handle-unlock-error)
(lambda (err) (signal (car err) (cdr err)))))
(should (equal
(if (eq system-type 'windows-nt)
'(permission-denied "Unlocking file")
'(file-error "Unlocking file"))
(seq-subseq (should-error (unlock-buffer)) 0 2))))))
(ert-deftest filelock-tests-kill-buffer-spoiled ()
"Check that `kill-buffer' fails if a lockfile is \"spoiled\"."
(skip-unless (not (eq system-type 'ms-dos))) ; no filelock support
(filelock-tests--fixture
;; Set the buffer modified with file locking temporarily disabled.
(let ((create-lockfiles nil))
(set-buffer-modified-p t))
(should-not (file-locked-p buffer-file-truename))
(filelock-tests--spoil-lock-file buffer-file-truename)
;; Kill the current buffer. Because the buffer is modified Emacs
;; will attempt to unlock it. Temporarily bind `yes-or-no-p' to a
;; function that fakes a "yes" answer for the "Buffer modified;
;; kill anyway?" prompt.
;;
;; File errors from unlocking files should call
;; `userlock--handle-unlock-error' (bug#46397).
(cl-letf (((symbol-function 'yes-or-no-p) #'always)
((symbol-function 'userlock--handle-unlock-error)
(lambda (err) (signal (car err) (cdr err)))))
(should (equal
(if (eq system-type 'windows-nt)
'(permission-denied "Unlocking file")
'(file-error "Unlocking file"))
(seq-subseq (should-error (kill-buffer)) 0 2))))))
(ert-deftest filelock-tests-detect-external-change ()
"Check that an external file modification is reported."
(skip-unless (not (eq system-type 'ms-dos))) ; no filelock support
(skip-unless (executable-find "touch"))
(skip-unless (executable-find "echo"))
(dolist (cl '(t nil))
(filelock-tests--fixture
(let ((create-lockfiles cl))
(write-region "foo" nil (buffer-file-name))
(revert-buffer nil 'noconfirm)
(should-not (file-locked-p (buffer-file-name)))
;; Just changing the file modification on disk doesn't hurt,
;; because file contents in buffer and on disk look equal.
(shell-command (format "touch %s" (buffer-file-name)))
(insert "bar")
(when cl (filelock-tests--should-be-locked))
;; Bug#53207: with `create-lockfiles' nil, saving the buffer
;; results in a prompt.
(cl-letf (((symbol-function 'yes-or-no-p)
(lambda (_) (ert-fail "Test failed unexpectedly"))))
(save-buffer))
(should-not (file-locked-p (buffer-file-name)))
;; Changing the file contents on disk hurts when buffer is
;; modified. There shall be a query, which we answer.
;; *Messages* buffer is checked for prompt.
(shell-command (format "echo bar >>%s" (buffer-file-name)))
(cl-letf (((symbol-function 'read-char-choice)
(lambda (prompt &rest _) (message "%s" prompt) ?y)))
(ert-with-message-capture captured-messages
;; `ask-user-about-supersession-threat' does not work in
;; batch mode, let's simulate interactiveness.
(let (noninteractive)
(insert "baz"))
(should (string-match-p
(format
"^%s changed on disk; really edit the buffer\\?"
(file-name-nondirectory (buffer-file-name)))
captured-messages))))
(when cl (filelock-tests--should-be-locked))))))
(provide 'filelock-tests)
;;; filelock-tests.el ends here