Fix Bug#26127

* lisp/filenotify.el (file-notify--rm-descriptor): Check, that
there is a function which could be called.  (Bug#26127)

* test/lisp/filenotify-tests.el (file-notify--test-cleanup):
Clear also `file-notify-descriptors'.
(file-notify--test-make-temp-name): Move up.
(file-notify-test02-rm-watch): New test.
(file-notify-test03-events, file-notify-test04-autorevert)
(file-notify-test05-file-validity)
(file-notify-test06-dir-validity)
(file-notify-test07-many-events, file-notify-test08-backup)
(file-notify-test09-watched-file-in-watched-dir)
(file-notify-test10-sufficient-resources): Rename.

2 files changed, 77 insertions, 26 deletions

diff --git a/lisp/filenotify.el b/lisp/filenotify.el
index 1de5420f1e7..7eb6229976a 100644
--- a/lisp/filenotify.el
+++ b/lisp/filenotify.el
@@ -62,9 +62,10 @@ If it is registered in `file-notify-descriptors', a stopped event is sent."
 
     (when (consp registered)
       ;; Send `stopped' event.
-      (funcall
-       (cdr (assoc file (cdr registered)))
-       `(,descriptor stopped ,(if file (expand-file-name file dir) dir)))
+      (when (consp (assoc file (cdr registered)))
+        (funcall
+         (cdr (assoc file (cdr registered)))
+         `(,descriptor stopped ,(if file (expand-file-name file dir) dir))))
 
       ;; Modify `file-notify-descriptors'.
       (if (not file)
diff --git a/test/lisp/filenotify-tests.el b/test/lisp/filenotify-tests.el
index dcd83a3ef3b..72080322379 100644
--- a/test/lisp/filenotify-tests.el
+++ b/test/lisp/filenotify-tests.el
@@ -150,6 +150,9 @@ Return nil when any other file notification watch is still active."
       (tramp-cleanup-connection
        (tramp-dissect-file-name temporary-file-directory) nil 'keep-password)))
 
+  (when (hash-table-p file-notify-descriptors)
+    (clrhash file-notify-descriptors))
+
   (setq file-notify--test-tmpfile nil
         file-notify--test-tmpfile1 nil
         file-notify--test-desc nil
@@ -332,6 +335,58 @@ This returns only for the local case and gfilenotify; otherwise it is nil.
 (file-notify--deftest-remote file-notify-test01-add-watch
   "Check `file-notify-add-watch' for remote files.")
 
+(defun file-notify--test-make-temp-name ()
+  "Create a temporary file name for test."
+  (expand-file-name
+   (make-temp-name "file-notify-test") temporary-file-directory))
+
+;; This test is inspired by Bug#26127.
+(ert-deftest file-notify-test02-rm-watch ()
+  "Check `file-notify-rm-watch'."
+  (skip-unless (file-notify--test-local-enabled))
+
+  (unwind-protect
+      (progn
+        ;; Check, that `file-notify-rm-watch' works.
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                temporary-file-directory '(change) #'ignore)))
+        (file-notify-rm-watch file-notify--test-desc)
+
+        ;; Check, that any parameter is accepted.
+        (condition-case err
+            (progn
+              (file-notify-rm-watch nil)
+              (file-notify-rm-watch 0)
+              (file-notify-rm-watch "foo")
+              (file-notify-rm-watch 'foo))
+          (error (ert-fail err)))
+
+        ;; Check, that no error is returned removing a watch descriptor twice.
+        (setq file-notify--test-tmpfile (file-notify--test-make-temp-name)
+              file-notify--test-tmpfile1 (file-notify--test-make-temp-name))
+        (should
+         (setq file-notify--test-desc
+               (file-notify-add-watch
+                file-notify--test-tmpfile '(change) #'ignore)))
+        (should
+         (setq file-notify--test-desc1
+               (file-notify-add-watch
+                file-notify--test-tmpfile1 '(change) #'ignore)))
+        (file-notify-rm-watch file-notify--test-desc)
+        (file-notify-rm-watch file-notify--test-desc)
+        (file-notify-rm-watch file-notify--test-desc1)
+
+        ;; The environment shall be cleaned up.
+        (file-notify--test-cleanup-p))
+
+    ;; Cleanup.
+    (file-notify--test-cleanup)))
+
+(file-notify--deftest-remote file-notify-test02-rm-watch
+  "Check `file-notify-rm-watch' for remote files.")
+
 (defun file-notify--test-event-test ()
   "Ert test function to be called by `file-notify--test-event-handler'.
 We cannot pass arguments, so we assume that `file-notify--test-event'
@@ -368,11 +423,6 @@ and the event to `file-notify--test-events'."
             file-notify--test-results
             (append file-notify--test-results `(,result))))))
 
-(defun file-notify--test-make-temp-name ()
-  "Create a temporary file name for test."
-  (expand-file-name
-   (make-temp-name "file-notify-test") temporary-file-directory))
-
 (defun file-notify--test-with-events-check (events)
   "Check whether received events match one of the EVENTS alternatives."
   (let (result)
@@ -436,7 +486,7 @@ delivered."
      ;; One of the possible event sequences shall match.
      (should (file-notify--test-with-events-check events))))
 
-(ert-deftest file-notify-test02-events ()
+(ert-deftest file-notify-test03-events ()
   "Check file creation/change/removal notifications."
   (skip-unless (file-notify--test-local-enabled))
 
@@ -658,7 +708,7 @@ delivered."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test02-events
+(file-notify--deftest-remote file-notify-test03-events
   "Check file creation/change/removal notifications for remote files.")
 
 (require 'autorevert)
@@ -666,7 +716,7 @@ delivered."
       auto-revert-remote-files t
       auto-revert-stop-on-user-input nil)
 
-(ert-deftest file-notify-test03-autorevert ()
+(ert-deftest file-notify-test04-autorevert ()
   "Check autorevert via file notification."
   (skip-unless (file-notify--test-local-enabled))
 
@@ -752,10 +802,10 @@ delivered."
       (ignore-errors (kill-buffer buf))
       (file-notify--test-cleanup))))
 
-(file-notify--deftest-remote file-notify-test03-autorevert
+(file-notify--deftest-remote file-notify-test04-autorevert
   "Check autorevert via file notification for remote files.")
 
-(ert-deftest file-notify-test04-file-validity ()
+(ert-deftest file-notify-test05-file-validity ()
   "Check `file-notify-valid-p' for files."
   (skip-unless (file-notify--test-local-enabled))
 
@@ -864,10 +914,10 @@ delivered."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test04-file-validity
+(file-notify--deftest-remote file-notify-test05-file-validity
   "Check `file-notify-valid-p' via file notification for remote files.")
 
-(ert-deftest file-notify-test05-dir-validity ()
+(ert-deftest file-notify-test06-dir-validity ()
   "Check `file-notify-valid-p' for directories."
   (skip-unless (file-notify--test-local-enabled))
 
@@ -922,10 +972,10 @@ delivered."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test05-dir-validity
+(file-notify--deftest-remote file-notify-test06-dir-validity
   "Check `file-notify-valid-p' via file notification for remote directories.")
 
-(ert-deftest file-notify-test06-many-events ()
+(ert-deftest file-notify-test07-many-events ()
   "Check that events are not dropped."
   :tags '(:expensive-test)
   (skip-unless (file-notify--test-local-enabled))
@@ -993,10 +1043,10 @@ delivered."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test06-many-events
+(file-notify--deftest-remote file-notify-test07-many-events
    "Check that events are not dropped for remote directories.")
 
-(ert-deftest file-notify-test07-backup ()
+(ert-deftest file-notify-test08-backup ()
   "Check that backup keeps file notification."
   (skip-unless (file-notify--test-local-enabled))
 
@@ -1072,10 +1122,10 @@ delivered."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test07-backup
+(file-notify--deftest-remote file-notify-test08-backup
   "Check that backup keeps file notification for remote files.")
 
-(ert-deftest file-notify-test08-watched-file-in-watched-dir ()
+(ert-deftest file-notify-test09-watched-file-in-watched-dir ()
   "Watches a directory and a file in that directory separately.
 Checks that the callbacks are only called with events with
 descriptors that were issued when registering the watches.  This
@@ -1205,10 +1255,10 @@ the file watch."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test08-watched-file-in-watched-dir
-  "Check `file-notify-test08-watched-file-in-watched-dir' for remote files.")
+(file-notify--deftest-remote file-notify-test09-watched-file-in-watched-dir
+  "Check `file-notify-test09-watched-file-in-watched-dir' for remote files.")
 
-(ert-deftest file-notify-test09-sufficient-resources ()
+(ert-deftest file-notify-test10-sufficient-resources ()
   "Check that file notification does not use too many resources."
   :tags '(:expensive-test)
   (skip-unless (file-notify--test-local-enabled))
@@ -1249,8 +1299,8 @@ the file watch."
     ;; Cleanup.
     (file-notify--test-cleanup)))
 
-(file-notify--deftest-remote file-notify-test09-sufficient-resources
-  "Check `file-notify-test09-sufficient-resources' for remote files.")
+(file-notify--deftest-remote file-notify-test10-sufficient-resources
+  "Check `file-notify-test10-sufficient-resources' for remote files.")
 
 (defun file-notify-test-all (&optional interactive)
   "Run all tests for \\[file-notify]."