Use file notification in autorevert also for recreated files

* lisp/autorevert.el (auto-revert-mode)
(global-auto-revert-mode, auto-revert-notify-add-watch)
(auto-revert-notify-handler, auto-revert-handler): Do not use
buffer local `auto-revert-use-notify' anymore.

* test/lisp/autorevert-tests.el
(auto-revert-test02-auto-revert-deleted-file): Adapt test in
order to check, that file notification is reenabled when possible.

lisp/autorevert.el

@@ -373,7 +373,7 @@ without being changed in the part that is already in the buffer."
          'kill-buffer-hook
          #'auto-revert-remove-current-buffer
          nil t))
-    (when auto-revert-use-notify (auto-revert-notify-rm-watch))
+    (when auto-revert-notify-watch-descriptor (auto-revert-notify-rm-watch))
     (auto-revert-remove-current-buffer))
   (auto-revert-set-timer)
   (when auto-revert-mode
@@ -486,7 +486,7 @@ specifies in the mode line."
       (auto-revert-buffers)
     (dolist (buf (buffer-list))
       (with-current-buffer buf
-	(when auto-revert-use-notify
+	(when auto-revert-notify-watch-descriptor
 	  (auto-revert-notify-rm-watch))))))
 
 (defun auto-revert-set-timer ()
@@ -524,38 +524,31 @@ will use an up-to-date value of `auto-revert-interval'"
 (defun auto-revert-notify-add-watch ()
   "Enable file notification for current buffer's associated file."
   ;; We can assume that `buffer-file-name' and
-  ;; `auto-revert-use-notify' are non-nil.
-  (if (or (string-match auto-revert-notify-exclude-dir-regexp
-			(expand-file-name default-directory))
-	  (file-symlink-p (or buffer-file-name default-directory)))
-
-      ;; Fallback to file checks.
-      (setq-local auto-revert-use-notify nil)
-
-    (when (not auto-revert-notify-watch-descriptor)
-      (setq auto-revert-notify-watch-descriptor
-	    (ignore-errors
-	      (if buffer-file-name
-		  (file-notify-add-watch
-		   (expand-file-name buffer-file-name default-directory)
-		   '(change attribute-change)
-		   'auto-revert-notify-handler)
+  ;; `auto-revert-notify-watch-descriptor' are non-nil.
+  (unless (or auto-revert-notify-watch-descriptor
+              (string-match auto-revert-notify-exclude-dir-regexp
+			    (expand-file-name default-directory))
+	      (file-symlink-p (or buffer-file-name default-directory)))
+    (setq auto-revert-notify-watch-descriptor
+	  (ignore-errors
+	    (if buffer-file-name
 		(file-notify-add-watch
-		 (expand-file-name default-directory)
-		 '(change)
-		 'auto-revert-notify-handler))))
-      (if auto-revert-notify-watch-descriptor
-	  (progn
-	    (puthash
-	     auto-revert-notify-watch-descriptor
-	     (cons (current-buffer)
-		   (gethash auto-revert-notify-watch-descriptor
-			    auto-revert-notify-watch-descriptor-hash-list))
-	     auto-revert-notify-watch-descriptor-hash-list)
-	    (add-hook 'kill-buffer-hook
-		      #'auto-revert-notify-rm-watch nil t))
-	;; Fallback to file checks.
-	(setq-local auto-revert-use-notify nil)))))
+		 (expand-file-name buffer-file-name default-directory)
+		 '(change attribute-change)
+		 'auto-revert-notify-handler)
+	      (file-notify-add-watch
+	       (expand-file-name default-directory)
+	       '(change)
+	       'auto-revert-notify-handler))))
+    (when auto-revert-notify-watch-descriptor
+      (setq auto-revert-notify-modified-p t)
+      (puthash
+      auto-revert-notify-watch-descriptor
+       (cons (current-buffer)
+	     (gethash auto-revert-notify-watch-descriptor
+		      auto-revert-notify-watch-descriptor-hash-list))
+       auto-revert-notify-watch-descriptor-hash-list)
+      (add-hook 'kill-buffer-hook #'auto-revert-notify-rm-watch nil t))))
 
 ;; If we have file notifications, we want to update the auto-revert buffers
 ;; immediately when a notification occurs. Since file updates can happen very
@@ -611,8 +604,7 @@ no more reverts are possible until the next call of
                                 (file-name-nondirectory buffer-file-name)))
                           ;; A buffer w/o a file, like dired.
                           (null buffer-file-name)))
-                (auto-revert-notify-rm-watch)
-                (setq-local auto-revert-use-notify nil))))
+                (auto-revert-notify-rm-watch))))
 
         ;; Loop over all buffers, in order to find the intended one.
         (cl-dolist (buffer buffers)
@@ -651,11 +643,9 @@ no more reverts are possible until the next call of
   "Check if auto-revert is active (in current buffer or globally)."
   (or auto-revert-mode
       auto-revert-tail-mode
-      (and
-       global-auto-revert-mode
-       (not global-auto-revert-ignore-buffer)
-       (not (memq major-mode
-		  global-auto-revert-ignore-modes)))))
+      (and global-auto-revert-mode
+           (not global-auto-revert-ignore-buffer)
+           (not (memq major-mode global-auto-revert-ignore-modes)))))
 
 (defun auto-revert-handler ()
   "Revert current buffer, if appropriate.
@@ -669,7 +659,7 @@ This is an internal function used by Auto-Revert Mode."
           (if buffer-file-name
               (and (or auto-revert-remote-files
                        (not (file-remote-p buffer-file-name)))
-                   (or (not auto-revert-use-notify)
+                   (or (not auto-revert-notify-watch-descriptor)
                        auto-revert-notify-modified-p)
                    (if auto-revert-tail-mode
                        (and (file-readable-p buffer-file-name)

test/lisp/autorevert-tests.el

@@ -161,7 +161,7 @@ This expects `auto-revert--messages' to be bound by
   :tags '(:expensive-test)
 
   (let ((tmpfile (make-temp-file "auto-revert-test"))
-        buf)
+        buf desc)
     (unwind-protect
 	(progn
           (write-region "any text" nil tmpfile nil 'no-message)
@@ -174,6 +174,7 @@ This expects `auto-revert--messages' to be bound by
             (sleep-for 1)
             (auto-revert-mode 1)
             (should auto-revert-mode)
+            (setq desc auto-revert-notify-watch-descriptor)
 
             ;; Remove file while reverting.  We simulate this by
             ;; modifying `before-revert-hook'.
@@ -192,7 +193,7 @@ This expects `auto-revert--messages' to be bound by
             (should (string-match "any text" (buffer-string)))
             ;; With w32notify, the 'stopped' events are not sent.
             (or (eq file-notify--library 'w32notify)
-                (should-not auto-revert-use-notify))
+                (should-not auto-revert-notify-watch-descriptor))
 
             ;; Once the file has been recreated, the buffer shall be
             ;; reverted.
@@ -203,6 +204,11 @@ This expects `auto-revert--messages' to be bound by
               (auto-revert--wait-for-revert buf))
             ;; Check, that the buffer has been reverted.
             (should (string-match "another text" (buffer-string)))
+            ;; When file notification is used, it must be reenabled
+            ;; after recreation of the file.  We cannot expect that
+            ;; the descriptor is the same, so we just check the
+            ;; existence.
+            (should (eq (null desc) (null auto-revert-notify-watch-descriptor)))
 
             ;; An empty file shall still be reverted.
             (ert-with-message-capture auto-revert--messages