;;; filelock-tests.el --- test file locking -*- lexical-binding: t; -*-

;; Copyright (C) 2021  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.

;;; Code:

(require 'ert)

(defun filelock-tests--call-with-fixture (body)
  (let ((test-dir (make-temp-file "filelock-tests-" t)))
    (unwind-protect
        (let ((file-name (concat (file-name-as-directory test-dir))))
          (with-temp-buffer
            (setq-local buffer-file-name file-name)
            (setq-local buffer-file-truename file-name)
            (unwind-protect
                (save-current-buffer
                  (let ((create-lockfiles t))
                    (funcall body)))
              (set-buffer-modified-p nil))))
      (delete-directory test-dir t nil))))

(defmacro filelock-tests--with-fixture (&rest body)
  "Create a test fixture and evaluate BODY there like `progn'.
Create a temporary directory, then create a temporary buffer and
set it the variable `buffer-file-name' and `buffer-file-truename'
to it, let bind `create-lockfiles' to 't' and evaluate BODY."
  (declare (indent 0))
  `(filelock-tests--call-with-fixture
    (lambda () ,@body)))

(defun filelock-tests--call-with-directory-modes (modes body)
  (let* ((dir (file-name-directory (buffer-file-name)))
         (original-modes (file-modes dir)))
    (set-file-modes dir modes)
    (unwind-protect
        (funcall body)
      (set-file-modes dir original-modes))))

(defmacro filelock-tests--with-directory-modes (modes &rest body)
  "Evaluate BODY forms with directory MODES set.
The directory is taken from the buffer local variable
`buffer-file-name'.  Afterwards, restore the modes to what they
were."
  (declare (indent 1))
  `(filelock-tests--call-with-directory-modes
    ,modes (lambda () ,@body)))

(ert-deftest filelock-tests-lock-buffer-permission-denied ()
  "Check that locking a buffer in a directory with no write
permissions does not work."
  (filelock-tests--with-fixture
      (should (not (file-locked-p (buffer-file-name))))
     (filelock-tests--with-directory-modes #o500
       ;; FIXME: (lock-buffer) should raise some sort of
       ;; error/warning here that we should verify in test.
       ;; Currently lock_file() ignores errors from lock_if_free().
       ;; See the related FIXME in filelock.c.
       (lock-buffer)
       (should (not (file-locked-p (buffer-file-name)))))))

(ert-deftest filelock-tests-file-locked-p-permission-denied ()
  "Check that `file-locked-p' fails if the directory is inaccesible."
  (filelock-tests--with-fixture
    (filelock-tests--with-directory-modes #o000
      (set-buffer-modified-p t)
      ;; FIXME: Bug#46397: `file-locked-p' currently signals errors,
      ;; but this prevents the user from killing the buffer.  It also
      ;; prevents Emacs shutdown.
      (should
       (equal
        (butlast (should-error (file-locked-p (buffer-file-name)))
                 2)
        '(file-error "Testing file lock"))))))

(ert-deftest filelock-tests-unlock-permission-denied ()
  "Check that `unlock-buffer' fails in directories that cannot be
modified."
  (filelock-tests--with-fixture
    (set-buffer-modified-p t)
    (lock-buffer)
    (should (file-locked-p (buffer-file-name)))
    (filelock-tests--with-directory-modes #o500
      ;; FIXME: Bug#46397: `unlock-buffer' currently signals errors,
      ;; but this prevents the user from killing the buffer.  It also
      ;; prevents Emacs shutdown.
      (should
       (equal
        (butlast (should-error (unlock-buffer))
                 2)
        '(file-error "Unlocking file"))))))

(provide 'filelock-tests)

;;; filelock-tests.el ends here