emacs-31 a94a33827b4: Avoid an unusual error when visiting a directory in Dired

branch: emacs-31
commit a94a33827b4048accf43b93d3cd7958b1832559f
Author: Stephen Berman <[email protected]>
Commit: Stephen Berman <[email protected]>

    Avoid an unusual error when visiting a directory in Dired
    
    * lisp/dired.el (dired-internal-noselect): Unset
    'dired--ls-error-buffer' before calling 'dired-readin'.  This is a
    safeguard to prevent an error when visiting a directory in Dired,
    which apparently happens when the variable somehow gets set even
    though 'ls' has not emitted an error message (bug#80499, Message #218).
    
    * test/lisp/dired-tests.el (dired-test-set-dired--ls-error-buffer): New test.
---
 lisp/dired.el            | 18 ++++++++++++++----
 test/lisp/dired-tests.el | 10 ++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/lisp/dired.el b/lisp/dired.el
index 9ce3f042f6b..26e698341d8 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -1459,10 +1459,20 @@ The return value is the target column for the file names."
       ;; (buffer-local), so we can call dired-readin:
       (let ((failed t))
 	(unwind-protect
-	    (progn (dired-readin)
-                   (unless (and dired--ls-error-buffer
-                                (get-buffer "*ls error*"))
-		     (setq failed nil)))
+            (progn
+              ;; `dired--ls-error-buffer' should only be set in
+              ;; `insert-directory', and if `ls' errors and the buffer
+              ;; displaying the error message pops ups,
+              ;; `dired--ls-error-buffer' is then unset.  But if for
+              ;; some reason it gets set before the next Dired
+              ;; buffer-display command is invoked, this can raise an
+              ;; error, so ensure the variable is unset before reading
+              ;; the directory contents into a Dired buffer.
+              (setq dired--ls-error-buffer nil)
+              (dired-readin)
+              (unless (and dired--ls-error-buffer
+                           (get-buffer "*ls error*"))
+                (setq failed nil)))
 	  ;; If either `dired-readin' failed (e.g. if parent directories
 	  ;; are inaccessible) or `ls' errored, don't leave the Dired
 	  ;; buffer around.
diff --git a/test/lisp/dired-tests.el b/test/lisp/dired-tests.el
index f77d56637fd..65ca58cc705 100644
--- a/test/lisp/dired-tests.el
+++ b/test/lisp/dired-tests.el
@@ -820,5 +820,15 @@ of the value of `dired-auto-toggle-b-switch'."
   (let ((dired-auto-toggle-b-switch nil))
     (dired-test--filename-with-backslash-n)))
 
+(ert-deftest dired-test-set-dired--ls-error-buffer () ; bug#80499, Message #218
+  "Test visiting a directory after setting `dired--ls-error-buffer'."
+  (let ((dir (ert-resource-file (file-name-as-directory "test-dir"))))
+    (make-directory dir t)
+    (setq dired--ls-error-buffer (get-buffer-create "*ls error*"))
+    (find-file dir)
+    (should (equal list-buffers-directory dir))
+    (kill-buffer (current-buffer))
+    (delete-directory dir)))
+
 (provide 'dired-tests)
 ;;; dired-tests.el ends here