Backport kqueue integration from master

* configure.ac (--with-file-notification): Add kqueue.
(top): Remove special test for "${HAVE_NS}" and
${with_file_notification}, this is handled inside gfilenotify
tests.  Add kqueue tests.  Use NOTIFY_CFLAGS and NOTIFY_LIBS
instead of library specific variables.  Add error message for
gfile on Nextstep.

* doc/lispref/os.texi (File Notifications): Add kqueue as backend.
Fix some glitches in the example.

* etc/NEWS: Mention kqueue.

* lisp/filenotify.el (file-notify--library)
(file-notify-descriptors, file-notify-callback)
(file-notify-add-watch, file-notify-rm-watch)
(file-notify-valid-p): Add kqueue support.
(file-notify--rm-descriptor): Remove WHAT arg.

* src/Makefile.in: Use NOTIFY_CFLAGS and NOTIFY_LIBS.

* src/emacs.c (main): Call globals_of_kqueue and syms_of_kqueue.

* src/inotify.c (inotifyevent_to_event): Extract file name from
watch_object if the event doesn't provide it.
(Finotify_add_watch): Add file name to watch_object.

* src/keyboard.c (make_lispy_event): Check also for HAVE_KQUEUE.

* src/kqueue.c: New file.

* src/lisp.h: Declare extern globals_of_kqueue and syms_of_kqueue.

* test/automated/file-notify-tests.el
(file-notify--test-expected-events): Remove.
(file-notify--test-cleanup): Do not set that variable.
(file-notify--test-timeout) Use different timeouts for
different libraries.
(file-notify--test-library): New defun.
(file-notify--test-event-test): Make stronger checks.
(file-notify--test-with-events): EVENTS can also be a list of
lists.  Flush outstanding events before running the body.
Make timeout heuristically depend on the number of events.
(file-notify-test01-add-watch, file-notify-test02-events)
(file-notify-test04-file-validity, file-notify-test05-dir-validity):
Rewrite in order to call file monitors but directory monitors.
(file-notify-test02-events, file-notify-test04-file-validity): Do
not skip cygwin tests.  Add additional test for file creation.
Adapt expected result for different backends.
(file-notify-test03-autorevert): Some of the tests don't work for
w32notify.
(file-notify-test06-many-events): New test.

1 files changed, 405 insertions, 180 deletions

diff --git a/test/automated/file-notify-tests.el b/test/automated/file-notify-tests.el
index 7bf7b0b3d15..de64f5086d2 100644
--- a/test/automated/file-notify-tests.el
+++ b/test/automated/file-notify-tests.el
@@ -61,11 +61,14 @@
 (defvar file-notify--test-results nil)
 (defvar file-notify--test-event nil)
 (defvar file-notify--test-events nil)
-(defvar file-notify--test-expected-events nil)
 
 (defun file-notify--test-timeout ()
   "Timeout to wait for arriving events, in seconds."
-  (if (file-remote-p temporary-file-directory) 6 3))
+  (cond
+   ((file-remote-p temporary-file-directory) 6)
+   ((string-equal (file-notify--test-library) "w32notify") 20)
+   ((eq system-type 'cygwin) 10)
+   (t 3)))
 
 (defun file-notify--test-cleanup ()
   "Cleanup after a test."
@@ -89,8 +92,7 @@
         file-notify--test-tmpfile1 nil
         file-notify--test-desc nil
         file-notify--test-results nil
-        file-notify--test-events nil
-        file-notify--test-expected-events nil)
+        file-notify--test-events nil)
   (when file-notify--test-event
     (error "file-notify--test-event should not be set but bound dynamically")))
 
@@ -133,6 +135,18 @@ being the result.")
   ;; Return result.
   (cdr file-notify--test-remote-enabled-checked))
 
+(defun file-notify--test-library ()
+  "The used library for the test, as a string.
+In the remote case, it is the process name which runs on the
+remote host, or nil."
+  (if (null (file-remote-p temporary-file-directory))
+      (symbol-name file-notify--library)
+    (and (consp file-notify--test-remote-enabled-checked)
+         (processp (cdr file-notify--test-remote-enabled-checked))
+         (replace-regexp-in-string
+          "<[[:digit:]]+>\\'" ""
+          (process-name (cdr file-notify--test-remote-enabled-checked))))))
+
 (defmacro file-notify--deftest-remote (test docstring)
   "Define ert `TEST-remote' for remote files."
   (declare (indent 1))
@@ -151,12 +165,7 @@ being the result.")
   "Test availability of `file-notify'."
   (skip-unless (file-notify--test-local-enabled))
   ;; Report the native library which has been used.
-  (if (null (file-remote-p temporary-file-directory))
-      (message "Local library: `%s'" file-notify--library)
-    (message "Remote command: `%s'"
-             (replace-regexp-in-string
-              "<[[:digit:]]+>\\'" ""
-              (process-name (cdr file-notify--test-remote-enabled-checked)))))
+  (message "Library: `%s'" (file-notify--test-library))
   (should
    (setq file-notify--test-desc
          (file-notify-add-watch temporary-file-directory '(change) 'ignore)))
@@ -190,12 +199,13 @@ being the result.")
          (file-notify-add-watch
           temporary-file-directory '(change attribute-change) 'ignore)))
   (file-notify-rm-watch file-notify--test-desc)
-  ;; The file does not need to exist, just the upper directory.
+  (write-region "any text" nil file-notify--test-tmpfile nil 'no-message)
   (should
    (setq file-notify--test-desc
          (file-notify-add-watch
           file-notify--test-tmpfile '(change attribute-change) 'ignore)))
   (file-notify-rm-watch file-notify--test-desc)
+  (delete-file file-notify--test-tmpfile)
 
   ;; Check error handling.
   (should-error (file-notify-add-watch 1 2 3 4)
@@ -236,16 +246,17 @@ is bound somewhere."
   (should
    (or (string-equal (file-notify--event-file-name file-notify--test-event)
                      file-notify--test-tmpfile)
-       (string-equal (directory-file-name
-                      (file-name-directory
-                       (file-notify--event-file-name file-notify--test-event)))
-                     file-notify--test-tmpfile)))
+       (string-equal (file-notify--event-file-name file-notify--test-event)
+                     file-notify--test-tmpfile1)
+       (string-equal (file-notify--event-file-name file-notify--test-event)
+                     temporary-file-directory)))
   ;; Check the second file name if exists.
   (when (eq (nth 1 file-notify--test-event) 'renamed)
     (should
-     (string-equal
-      (file-notify--event-file1-name file-notify--test-event)
-      file-notify--test-tmpfile1))))
+     (or (string-equal (file-notify--event-file1-name file-notify--test-event)
+                       file-notify--test-tmpfile1)
+         (string-equal (file-notify--event-file1-name file-notify--test-event)
+                       temporary-file-directory)))))
 
 (defun file-notify--test-event-handler (event)
   "Run a test over FILE-NOTIFY--TEST-EVENT.
@@ -254,7 +265,7 @@ and the event to `file-notify--test-events'."
   (let* ((file-notify--test-event event)
          (result
           (ert-run-test (make-ert-test :body 'file-notify--test-event-test))))
-    ;; Do not add temporary files, this would confuse the checks.
+    ;; Do not add lock files, this would confuse the checks.
     (unless (string-match
              (regexp-quote ".#")
              (file-notify--event-file-name file-notify--test-event))
@@ -278,137 +289,246 @@ TIMEOUT is the maximum time to wait for, in seconds."
 
 (defmacro file-notify--test-with-events (events &rest body)
   "Run BODY collecting events and then compare with EVENTS.
-Don't wait longer than timeout seconds for the events to be delivered."
+EVENTS is either a simple list of events, or a list of lists of
+events, which represent different possible results.  Don't wait
+longer than timeout seconds for the events to be delivered."
   (declare (indent 1))
   (let ((outer (make-symbol "outer")))
-    `(let ((,outer file-notify--test-events))
-       (setq file-notify--test-expected-events
-             (append file-notify--test-expected-events ,events))
+    `(let* ((,outer file-notify--test-events)
+            (events (if (consp (car ,events)) ,events (list ,events)))
+            (max-length (apply 'max (mapcar 'length events)))
+            create-lockfiles result)
+       ;; Flush pending events.
+       (file-notify--wait-for-events
+        (file-notify--test-timeout)
+        (input-pending-p))
        (let (file-notify--test-events)
          ,@body
          (file-notify--wait-for-events
-          (file-notify--test-timeout)
-          (= (length ,events) (length file-notify--test-events)))
-         (should (equal ,events (mapcar #'cadr file-notify--test-events)))
+          ;; More events need more time.  Use some fudge factor.
+          (* (ceiling max-length 100) (file-notify--test-timeout))
+          (= max-length (length file-notify--test-events)))
+         ;; One of the possible results shall match.
+         (should
+          (dolist (elt events result)
+            (setq result
+                  (or result
+                      (equal elt (mapcar #'cadr file-notify--test-events))))))
          (setq ,outer (append ,outer file-notify--test-events)))
        (setq file-notify--test-events ,outer))))
 
 (ert-deftest file-notify-test02-events ()
   "Check file creation/change/removal notifications."
   (skip-unless (file-notify--test-local-enabled))
-  ;; Under cygwin there are so bad timings that it doesn't make sense to test.
-  (skip-unless (not (eq system-type 'cygwin)))
-
-  (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
-        file-notify--test-tmpfile1 (file-notify--test-make-temp-name))
 
   (unwind-protect
       (progn
-        ;; Check creation, change and deletion.
-        (setq file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) 'file-notify--test-event-handler))
-        (file-notify--test-with-events '(created changed deleted)
+        ;; Check file creation, change and deletion.  It doesn't work
+        ;; for cygwin and kqueue, because we don't use an implicit
+        ;; directory monitor (kqueue), or the timings are too bad (cygwin).
+        (unless (or (eq system-type 'cygwin)
+                    (string-equal (file-notify--test-library) "kqueue"))
+          (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+          (should
+           (setq file-notify--test-desc
+                 (file-notify-add-watch
+                  file-notify--test-tmpfile
+                  '(change) 'file-notify--test-event-handler)))
+          (file-notify--test-with-events
+              (cond
+               ;; cygwin recognizes only `deleted' and `stopped' events.
+               ((eq system-type 'cygwin)
+                '(deleted stopped))
+               (t '(created changed deleted stopped)))
+            (write-region
+             "another text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
+            (delete-file file-notify--test-tmpfile))
+          ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
+          (let (file-notify--test-events)
+            (file-notify-rm-watch file-notify--test-desc)))
+
+        ;; Check file change and deletion.
+        (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+        (write-region "any text" nil file-notify--test-tmpfile nil 'no-message)
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile
+                '(change) 'file-notify--test-event-handler)))
+        (file-notify--test-with-events
+            (cond
+             ;; cygwin recognizes only `deleted' and `stopped' events.
+             ((eq system-type 'cygwin)
+              '(deleted stopped))
+             ;; inotify and kqueue raise just one `changed' event.
+             ((or (string-equal "inotify" (file-notify--test-library))
+                  (string-equal "kqueue" (file-notify--test-library)))
+              '(changed deleted stopped))
+             ;; gfilenotify raises one or two `changed' events
+             ;; randomly, no chance to test.  So we accept both cases.
+             ((string-equal "gfilenotify" (file-notify--test-library))
+              '((changed deleted stopped)
+                (changed changed deleted stopped)))
+             (t '(changed changed deleted stopped)))
+          (read-event nil nil 0.1)
           (write-region
-           "any text" nil file-notify--test-tmpfile nil 'no-message)
+           "another text" nil file-notify--test-tmpfile nil 'no-message)
+          (read-event nil nil 0.1)
           (delete-file file-notify--test-tmpfile))
         ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
         (let (file-notify--test-events)
           (file-notify-rm-watch file-notify--test-desc))
 
-        ;; Check creation, change and deletion.  There must be a
-        ;; `stopped' event when deleting the directory.  It doesn't
-        ;; work for w32notify.
-        (unless (eq file-notify--library 'w32notify)
-          (make-directory file-notify--test-tmpfile)
-          (setq file-notify--test-desc
-                (file-notify-add-watch
-                 file-notify--test-tmpfile
-                 '(change) 'file-notify--test-event-handler))
+        ;; Check file creation, change and deletion when watching a
+        ;; directory.  There must be a `stopped' event when deleting
+        ;; the directory.
+        (let ((temporary-file-directory
+               (make-temp-file "file-notify-test-parent" t)))
+          (should
+           (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
+                 file-notify--test-desc
+                 (file-notify-add-watch
+                  temporary-file-directory
+                  '(change) 'file-notify--test-event-handler)))
           (file-notify--test-with-events
-              ;; There are two `deleted' events, for the file and for
-              ;; the directory.
-              '(created changed deleted deleted stopped)
+              (cond
+               ;; w32notify does raise a `stopped' event when a
+               ;; watched directory is deleted.
+               ((string-equal (file-notify--test-library) "w32notify")
+                '(created changed deleted))
+               ;; cygwin recognizes only `deleted' and `stopped' events.
+               ((eq system-type 'cygwin)
+                '(deleted stopped))
+               ;; There are two `deleted' events, for the file and for
+               ;; the directory.  Except for kqueue.
+               ((string-equal (file-notify--test-library) "kqueue")
+                '(created changed deleted stopped))
+               (t '(created changed deleted deleted stopped)))
+            (read-event nil nil 0.1)
             (write-region
-             "any text" nil (expand-file-name "foo" file-notify--test-tmpfile)
-             nil 'no-message)
-            (delete-directory file-notify--test-tmpfile 'recursive))
+             "any text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
+            (delete-directory temporary-file-directory 'recursive))
           ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
           (let (file-notify--test-events)
             (file-notify-rm-watch file-notify--test-desc)))
 
-        ;; Check copy.
-        (setq file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) 'file-notify--test-event-handler))
-        (should file-notify--test-desc)
-        (file-notify--test-with-events
-            ;; w32notify does not distinguish between `changed' and
-            ;; `attribute-changed'.
-            (if (eq file-notify--library 'w32notify)
-                '(created changed changed deleted)
-              '(created changed deleted))
-          (write-region
-           "any text" nil file-notify--test-tmpfile nil 'no-message)
-          (copy-file file-notify--test-tmpfile file-notify--test-tmpfile1)
-          ;; The next two events shall not be visible.
-          (set-file-modes file-notify--test-tmpfile 000)
-          (read-event nil nil 0.1) ; In order to distinguish the events.
-          (set-file-times file-notify--test-tmpfile '(0 0))
-          (delete-file file-notify--test-tmpfile)
-          (delete-file file-notify--test-tmpfile1))
-        ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
-        (let (file-notify--test-events)
-          (file-notify-rm-watch file-notify--test-desc))
+        ;; Check copy of files inside a directory.
+        (let ((temporary-file-directory
+               (make-temp-file "file-notify-test-parent" t)))
+          (should
+           (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
+                 file-notify--test-tmpfile1 (file-notify--test-make-temp-name)
+                 file-notify--test-desc
+                 (file-notify-add-watch
+                  temporary-file-directory
+                  '(change) 'file-notify--test-event-handler)))
+          (file-notify--test-with-events
+              (cond
+               ;; w32notify does not distinguish between `changed' and
+               ;; `attribute-changed'.
+               ((string-equal (file-notify--test-library) "w32notify")
+                '(created changed created changed changed changed changed
+                  deleted deleted))
+               ;; cygwin recognizes only `deleted' and `stopped' events.
+               ((eq system-type 'cygwin)
+                '(deleted stopped))
+               ;; There are three `deleted' events, for two files and
+               ;; for the directory.  Except for kqueue.
+               ((string-equal (file-notify--test-library) "kqueue")
+                '(created changed created changed deleted stopped))
+               (t '(created changed created changed
+                    deleted deleted deleted stopped)))
+            (read-event nil nil 0.1)
+            (write-region
+             "any text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
+            (copy-file file-notify--test-tmpfile file-notify--test-tmpfile1)
+            ;; The next two events shall not be visible.
+            (read-event nil nil 0.1)
+            (set-file-modes file-notify--test-tmpfile 000)
+            (read-event nil nil 0.1)
+            (set-file-times file-notify--test-tmpfile '(0 0))
+            (read-event nil nil 0.1)
+            (delete-directory temporary-file-directory 'recursive))
+          ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
+          (let (file-notify--test-events)
+            (file-notify-rm-watch file-notify--test-desc)))
 
-        ;; Check rename.
-        (setq file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) 'file-notify--test-event-handler))
-        (should file-notify--test-desc)
-        (file-notify--test-with-events '(created changed renamed)
-          (write-region
-           "any text" nil file-notify--test-tmpfile nil 'no-message)
-          (rename-file file-notify--test-tmpfile file-notify--test-tmpfile1)
-          ;; After the rename, we won't get events anymore.
-          (delete-file file-notify--test-tmpfile1))
-        ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
-        (let (file-notify--test-events)
-          (file-notify-rm-watch file-notify--test-desc))
+        ;; Check rename of files inside a directory.
+        (let ((temporary-file-directory
+               (make-temp-file "file-notify-test-parent" t)))
+          (should
+           (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
+                 file-notify--test-tmpfile1 (file-notify--test-make-temp-name)
+                 file-notify--test-desc
+                 (file-notify-add-watch
+                  temporary-file-directory
+                  '(change) 'file-notify--test-event-handler)))
+          (file-notify--test-with-events
+              (cond
+               ;; w32notify does not distinguish between `changed' and
+               ;; `attribute-changed'.
+               ((string-equal (file-notify--test-library) "w32notify")
+                '(created changed renamed deleted))
+               ;; cygwin recognizes only `deleted' and `stopped' events.
+               ((eq system-type 'cygwin)
+                '(deleted stopped))
+               ;; There are two `deleted' events, for the file and for
+               ;; the directory.  Except for kqueue.
+               ((string-equal (file-notify--test-library) "kqueue")
+                '(created changed renamed deleted stopped))
+               (t '(created changed renamed deleted deleted stopped)))
+            (read-event nil nil 0.1)
+            (write-region
+             "any text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
+            (rename-file file-notify--test-tmpfile file-notify--test-tmpfile1)
+            ;; After the rename, we won't get events anymore.
+            (read-event nil nil 0.1)
+            (delete-directory temporary-file-directory 'recursive))
+          ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
+          (let (file-notify--test-events)
+            (file-notify-rm-watch file-notify--test-desc)))
 
-        ;; Check attribute change.  It doesn't work for w32notify.
-        (unless (eq file-notify--library 'w32notify)
-          (setq file-notify--test-desc
-                (file-notify-add-watch
-                 file-notify--test-tmpfile
-                 '(attribute-change) 'file-notify--test-event-handler))
-          (file-notify--test-with-events
-              (if (file-remote-p temporary-file-directory)
-                  ;; In the remote case, `write-region' raises also an
-                  ;; `attribute-changed' event.
-                  '(attribute-changed attribute-changed attribute-changed)
-                '(attribute-changed attribute-changed))
-            ;; We must use short delays between the operations.
-            ;; Otherwise, not all events arrive us in the remote case.
-            (write-region
-             "any text" nil file-notify--test-tmpfile nil 'no-message)
-            (read-event nil nil 0.1)
-            (set-file-modes file-notify--test-tmpfile 000)
-            (read-event nil nil 0.1)
-            (set-file-times file-notify--test-tmpfile '(0 0))
-            (read-event nil nil 0.1)
-            (delete-file file-notify--test-tmpfile))
+        ;; Check attribute change.  Does not work for cygwin.
+        (unless (eq system-type 'cygwin)
+          (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+          (write-region
+           "any text" nil file-notify--test-tmpfile nil 'no-message)
+          (should
+           (setq file-notify--test-desc
+                 (file-notify-add-watch
+                  file-notify--test-tmpfile
+                  '(attribute-change) 'file-notify--test-event-handler)))
+          (file-notify--test-with-events
+              (cond
+               ;; w32notify does not distinguish between `changed' and
+               ;; `attribute-changed'.
+               ((string-equal (file-notify--test-library) "w32notify")
+                '(changed changed changed changed))
+               ;; For kqueue and in the remote case, `write-region'
+               ;; raises also an `attribute-changed' event.
+               ((or (string-equal (file-notify--test-library) "kqueue")
+                    (file-remote-p temporary-file-directory))
+                '(attribute-changed attribute-changed attribute-changed))
+               (t '(attribute-changed attribute-changed)))
+            (read-event nil nil 0.1)
+            (write-region
+             "any text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
+            (set-file-modes file-notify--test-tmpfile 000)
+            (read-event nil nil 0.1)
+            (set-file-times file-notify--test-tmpfile '(0 0))
+            (read-event nil nil 0.1)
+            (delete-file file-notify--test-tmpfile))
           ;; `file-notify-rm-watch' fires the `stopped' event.  Suppress it.
           (let (file-notify--test-events)
             (file-notify-rm-watch file-notify--test-desc)))
 
         ;; Check the global sequence again just to make sure that
         ;; `file-notify--test-events' has been set correctly.
-        (should (equal (mapcar #'cadr file-notify--test-events)
-                       file-notify--test-expected-events))
         (should file-notify--test-results)
         (dolist (result file-notify--test-results)
           (when (ert-test-failed-p result)
@@ -476,28 +596,31 @@ Don't wait longer than timeout seconds for the events to be delivered."
             (should (string-match "another text" (buffer-string)))
 
             ;; Stop file notification.  Autorevert shall still work via polling.
-            (file-notify-rm-watch auto-revert-notify-watch-descriptor)
-            (file-notify--wait-for-events
-             timeout (null auto-revert-use-notify))
-            (should-not auto-revert-use-notify)
-            (should-not auto-revert-notify-watch-descriptor)
-
-            ;; Modify file.  We wait for two seconds, in order to have
-            ;; another timestamp.  One second seems to be too short.
-            (with-current-buffer (get-buffer-create "*Messages*")
-              (narrow-to-region (point-max) (point-max)))
-            (sleep-for 2)
-            (write-region
-             "foo bla" nil file-notify--test-tmpfile nil 'no-message)
-
-            ;; Check, that the buffer has been reverted.
-            (with-current-buffer (get-buffer-create "*Messages*")
+            ;; It doesn't work for `w32notify'.
+            (unless (string-equal (file-notify--test-library) "w32notify")
+              (file-notify-rm-watch auto-revert-notify-watch-descriptor)
               (file-notify--wait-for-events
-               timeout
-               (string-match
-                (format-message "Reverting buffer `%s'." (buffer-name buf))
-                (buffer-string))))
-            (should (string-match "foo bla" (buffer-string)))))
+               timeout (null auto-revert-use-notify))
+              (should-not auto-revert-use-notify)
+              (should-not auto-revert-notify-watch-descriptor)
+
+              ;; Modify file.  We wait for two seconds, in order to
+              ;; have another timestamp.  One second seems to be too
+              ;; short.
+              (with-current-buffer (get-buffer-create "*Messages*")
+                (narrow-to-region (point-max) (point-max)))
+              (sleep-for 2)
+              (write-region
+               "foo bla" nil file-notify--test-tmpfile nil 'no-message)
+
+              ;; Check, that the buffer has been reverted.
+              (with-current-buffer (get-buffer-create "*Messages*")
+                (file-notify--wait-for-events
+                 timeout
+                 (string-match
+                  (format-message "Reverting buffer `%s'." (buffer-name buf))
+                  (buffer-string))))
+              (should (string-match "foo bla" (buffer-string))))))
 
       ;; Cleanup.
       (with-current-buffer "*Messages*" (widen))
@@ -510,51 +633,94 @@ Don't wait longer than timeout seconds for the events to be delivered."
 (ert-deftest file-notify-test04-file-validity ()
   "Check `file-notify-valid-p' for files."
   (skip-unless (file-notify--test-local-enabled))
-  ;; Under cygwin there are so bad timings that it doesn't make sense to test.
-  (skip-unless (not (eq system-type 'cygwin)))
 
   (unwind-protect
       (progn
-        (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
-              file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) #'file-notify--test-event-handler))
-        (file-notify--test-with-events '(created changed deleted)
+        (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+        (write-region "any text" nil file-notify--test-tmpfile nil 'no-message)
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile
+                '(change) #'file-notify--test-event-handler)))
+        (should (file-notify-valid-p file-notify--test-desc))
+        ;; After calling `file-notify-rm-watch', the descriptor is not
+        ;; valid anymore.
+        (file-notify-rm-watch file-notify--test-desc)
+        (should-not (file-notify-valid-p file-notify--test-desc))
+        (delete-file file-notify--test-tmpfile))
+
+    ;; Cleanup.
+    (file-notify--test-cleanup))
+
+  (unwind-protect
+      (progn
+        (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+        (write-region "any text" nil file-notify--test-tmpfile nil 'no-message)
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile
+                '(change) #'file-notify--test-event-handler)))
+        (file-notify--test-with-events
+            (cond
+             ;; cygwin recognizes only `deleted' and `stopped' events.
+             ((eq system-type 'cygwin)
+              '(deleted stopped))
+             ;; inotify and kqueue raise just one `changed' event.
+             ((or (string-equal "inotify" (file-notify--test-library))
+                  (string-equal "kqueue" (file-notify--test-library)))
+              '(changed deleted stopped))
+             ;; gfilenotify raises one or two `changed' events
+             ;; randomly, no chance to test.  So we accept both cases.
+             ((string-equal "gfilenotify" (file-notify--test-library))
+              '((changed deleted stopped)
+                (changed changed deleted stopped)))
+             (t '(changed changed deleted stopped)))
           (should (file-notify-valid-p file-notify--test-desc))
+          (read-event nil nil 0.1)
           (write-region
-           "any text" nil file-notify--test-tmpfile nil 'no-message)
+           "another text" nil file-notify--test-tmpfile nil 'no-message)
+          (read-event nil nil 0.1)
           (delete-file file-notify--test-tmpfile))
-        ;; After deleting the file, the descriptor is still valid.
-        (should (file-notify-valid-p file-notify--test-desc))
-        ;; After removing the watch, the descriptor must not be valid
-        ;; anymore.
-        (file-notify-rm-watch file-notify--test-desc)
-        (should-not (file-notify-valid-p file-notify--test-desc)))
+        ;; After deleting the file, the descriptor is not valid anymore.
+        (should-not (file-notify-valid-p file-notify--test-desc))
+        (file-notify-rm-watch file-notify--test-desc))
 
     ;; Cleanup.
     (file-notify--test-cleanup))
 
   (unwind-protect
-      ;; The batch-mode operation of w32notify is fragile (there's no
-      ;; input threads to send the message to).
-      ;(unless (and noninteractive (eq file-notify--library 'w32notify))
-      (unless (eq file-notify--library 'w32notify)
-        (let ((temporary-file-directory
+      ;; w32notify does not send a `stopped' event when deleting a
+      ;; directory.  The test does not work, therefore.
+      (unless (string-equal (file-notify--test-library) "w32notify")
+        (let ((temporary-file-directory
                (make-temp-file "file-notify-test-parent" t)))
-          (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
-                file-notify--test-desc
-                (file-notify-add-watch
-                 file-notify--test-tmpfile
-                 '(change) #'file-notify--test-event-handler))
-          (file-notify--test-with-events '(created changed deleted stopped)
-            (should (file-notify-valid-p file-notify--test-desc))
-            (write-region
-             "any text" nil file-notify--test-tmpfile nil 'no-message)
+          (should
+           (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
+                 file-notify--test-desc
+                 (file-notify-add-watch
+                  temporary-file-directory
+                  '(change) #'file-notify--test-event-handler)))
+          (file-notify--test-with-events
+              (cond
+               ;; cygwin recognizes only `deleted' and `stopped' events.
+               ((eq system-type 'cygwin)
+                '(deleted stopped))
+               ;; There are two `deleted' events, for the file and for
+               ;; the directory.  Except for kqueue.
+               ((string-equal (file-notify--test-library) "kqueue")
+                '(created changed deleted stopped))
+               (t '(created changed deleted deleted stopped)))
+            (should (file-notify-valid-p file-notify--test-desc))
+            (read-event nil nil 0.1)
+            (write-region
+             "any text" nil file-notify--test-tmpfile nil 'no-message)
+            (read-event nil nil 0.1)
             (delete-directory temporary-file-directory t))
-          ;; After deleting the parent directory, the descriptor must
-          ;; not be valid anymore.
-          (should-not (file-notify-valid-p file-notify--test-desc))))
+          ;; After deleting the parent directory, the descriptor must
+          ;; not be valid anymore.
+          (should-not (file-notify-valid-p file-notify--test-desc))))
 
     ;; Cleanup.
     (file-notify--test-cleanup)))
@@ -571,10 +737,11 @@ Don't wait longer than timeout seconds for the events to be delivered."
         (setq file-notify--test-tmpfile
               (file-name-as-directory (file-notify--test-make-temp-name)))
         (make-directory file-notify--test-tmpfile)
-        (setq file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) #'file-notify--test-event-handler))
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile
+                '(change) #'file-notify--test-event-handler)))
         (should (file-notify-valid-p file-notify--test-desc))
         ;; After removing the watch, the descriptor must not be valid
         ;; anymore.
@@ -590,20 +757,22 @@ Don't wait longer than timeout seconds for the events to be delivered."
   (unwind-protect
       ;; The batch-mode operation of w32notify is fragile (there's no
       ;; input threads to send the message to).
-      (unless (and noninteractive (eq file-notify--library 'w32notify))
+      (unless (and noninteractive
+                   (string-equal (file-notify--test-library) "w32notify"))
         (setq file-notify--test-tmpfile
               (file-name-as-directory (file-notify--test-make-temp-name)))
         (make-directory file-notify--test-tmpfile)
-        (setq file-notify--test-desc
-              (file-notify-add-watch
-               file-notify--test-tmpfile
-               '(change) #'file-notify--test-event-handler))
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile
+                '(change) #'file-notify--test-event-handler)))
         (should (file-notify-valid-p file-notify--test-desc))
         ;; After deleting the directory, the descriptor must not be
         ;; valid anymore.
         (delete-directory file-notify--test-tmpfile t)
         (file-notify--wait-for-events
-         (file-notify--test-timeout)
+         (file-notify--test-timeout)
          (not (file-notify-valid-p file-notify--test-desc)))
         (should-not (file-notify-valid-p file-notify--test-desc)))
 
@@ -613,6 +782,62 @@ Don't wait longer than timeout seconds for the events to be delivered."
 (file-notify--deftest-remote file-notify-test05-dir-validity
   "Check `file-notify-valid-p' via file notification for remote directories.")
 
+(ert-deftest file-notify-test06-many-events ()
+  "Check that events are not dropped."
+  :tags '(:expensive-test)
+  (skip-unless (file-notify--test-local-enabled))
+  ;; Under cygwin events arrive in random order.  Impossible to define a test.
+  (skip-unless (not (eq system-type 'cygwin)))
+
+  (setq file-notify--test-tmpfile (file-notify--test-make-temp-name))
+  (make-directory file-notify--test-tmpfile)
+  (should
+   (setq file-notify--test-desc
+         (file-notify-add-watch
+          file-notify--test-tmpfile
+          '(change) 'file-notify--test-event-handler)))
+  (unwind-protect
+      (let ((n 1000)
+            source-file-list target-file-list
+            (default-directory file-notify--test-tmpfile))
+        (dotimes (i n)
+          ;; It matters which direction we rename, at least for
+          ;; kqueue.  This backend parses directories in alphabetic
+          ;; order (x%d before y%d).  So we rename both directions.
+          (if (zerop (mod i 2))
+              (progn
+                (push (expand-file-name (format "x%d" i)) source-file-list)
+                (push (expand-file-name (format "y%d" i)) target-file-list))
+            (push (expand-file-name (format "y%d" i)) source-file-list)
+            (push (expand-file-name (format "x%d" i)) target-file-list)))
+        (file-notify--test-with-events (make-list (+ n n) 'created)
+          (let ((source-file-list source-file-list)
+                (target-file-list target-file-list))
+            (while (and source-file-list target-file-list)
+              (read-event nil nil 0.1)
+              (write-region "" nil (pop source-file-list) nil 'no-message)
+              (read-event nil nil 0.1)
+              (write-region "" nil (pop target-file-list) nil 'no-message))))
+        (file-notify--test-with-events
+            (cond
+             ;; w32notify fires both `deleted' and `renamed' events.
+             ((string-equal (file-notify--test-library) "w32notify")
+              (let (r)
+                (dotimes (_i n r)
+                  (setq r (append '(deleted renamed) r)))))
+             (t (make-list n 'renamed)))
+          (let ((source-file-list source-file-list)
+                (target-file-list target-file-list))
+            (while (and source-file-list target-file-list)
+              (rename-file (pop source-file-list) (pop target-file-list) t))))
+        (file-notify--test-with-events (make-list n 'deleted)
+          (dolist (file target-file-list)
+            (delete-file file))))
+    (file-notify--test-cleanup)))
+
+(file-notify--deftest-remote file-notify-test06-many-events
+   "Check that events are not dropped for remote directories.")
+
 (defun file-notify-test-all (&optional interactive)
   "Run all tests for \\[file-notify]."
   (interactive "p")
@@ -623,7 +848,7 @@ Don't wait longer than timeout seconds for the events to be delivered."
 ;; TODO:
 
 ;; * For w32notify, no stopped events arrive when a directory is removed.
-;; * Try to handle arriving events under cygwin reliably.
+;; * Check, why cygwin recognizes only `deleted' and `stopped' events.
 
 (provide 'file-notify-tests)
 ;;; file-notify-tests.el ends here