Fix some make-directory bugs

* lisp/files.el (files--ensure-directory): New function.
(make-directory): Use it to avoid bugs when (make-directory FOO t)
is invoked on a non-directory, or on a directory hierarchy that
is being built by some other process while Emacs is running.
* test/lisp/files-tests.el (files-tests--make-directory): New test.

1 files changed, 20 insertions, 11 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 43aec8173d9..85e649fbb59 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -5320,6 +5320,14 @@ instance of such commands."
       (rename-buffer (generate-new-buffer-name base-name))
       (force-mode-line-update))))
 
+(defun files--ensure-directory (dir)
+  "Make directory DIR if it is not already a directory.  Return nil."
+  (condition-case err
+      (make-directory-internal dir)
+    (file-already-exists
+     (unless (file-directory-p dir)
+       (signal (car err) (cdr err))))))
+
 (defun make-directory (dir &optional parents)
   "Create the directory DIR and optionally any nonexistent parent dirs.
 If DIR already exists as a directory, signal an error, unless
@@ -5348,18 +5356,19 @@ raised."
       (if (not parents)
           (make-directory-internal dir)
         (let ((dir (directory-file-name (expand-file-name dir)))
-              create-list)
-          (while (and (not (file-exists-p dir))
-                      ;; If directory is its own parent, then we can't
-                      ;; keep looping forever
-                      (not (equal dir
-                                  (directory-file-name
-                                   (file-name-directory dir)))))
+              create-list parent)
+          (while (progn
+                   (setq parent (directory-file-name
+                                 (file-name-directory dir)))
+                   (condition-case err
+                       (files--ensure-directory dir)
+                     (file-missing
+                      ;; Do not loop if root does not exist (Bug#2309).
+                      (not (string= dir parent)))))
             (setq create-list (cons dir create-list)
-                  dir (directory-file-name (file-name-directory dir))))
-          (while create-list
-            (make-directory-internal (car create-list))
-            (setq create-list (cdr create-list))))))))
+                  dir parent))
+          (dolist (dir create-list)
+            (files--ensure-directory dir)))))))
 
 (defconst directory-files-no-dot-files-regexp
   "^\\([^.]\\|\\.\\([^.]\\|\\..\\)\\).*"