bug#62732: 29.0.60; uniquify-trailing-separator-p affects any buffer whose name matches a dir in CWD

[sbaugh]

This patch takes the approach of pulling uniquify-trailing-separator-p
out of uniquify and putting it into dired; now the trailing separator is
specified when the dired buffer is created.  This is incidentally also
vastly more efficient: The old way did n² filesystem accesses which is
not something we should be doing on every buffer creation/rename.

Also, this approach is in line with other simplifications of uniquify
that I'd like to make (as part of implementing bug#62621).

Also, now there are tests for uniquify.

diff --git a/lisp/dired.el b/lisp/dired.el
index 4a4ecc901c4..12629dbbd87 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -490,6 +490,17 @@ dired-guess-shell-znew-switches
                  (string :tag "Switches"))
   :version "29.1")
 
+(defcustom dired-trailing-separator nil
+  "If non-nil, add a file name separator to dired buffer names.
+For example, \"dir/\" instead of \"dir\".
+
+Normally the separator is added at the end and matches the
+platform convention for path separators.  If
+`uniquify-buffer-name-style' is `reverse', add the separator at
+the beginning, and use `uniquify-separator' for the separator."
+  :type 'boolean
+  :group 'dired)
+
 
 ;;; Internal variables
 
@@ -1285,6 +1296,19 @@ dired--align-all-files
               (insert-char ?\s distance 'inherit))
             (forward-line)))))))
 
+(defun dired--create-buffer (dirname)
+  "Create a buffer with an appropriate name for visiting this directory.
+
+Obeys `dired-trailing-separator'."
+  (let* ((filename (directory-file-name dirname))
+         (base (file-name-nondirectory filename)))
+    (create-file-buffer filename
+                        (if dired-trailing-separator
+                            (cond ((eq uniquify-buffer-name-style 'forward)
+                                  (file-name-as-directory base))
+                                 ((eq uniquify-buffer-name-style 'reverse)
+                                  (concat (or uniquify-separator "\\") 
base)))))))
+
 (defun dired-internal-noselect (dir-or-list &optional switches mode)
   ;; If DIR-OR-LIST is a string and there is an existing dired buffer
   ;; for it, just leave buffer as it is (don't even call dired-revert).
@@ -1306,7 +1330,7 @@ dired-internal-noselect
         ;; Note that buffer already is in dired-mode, if found.
         (new-buffer-p (null buffer)))
     (or buffer
-        (setq buffer (create-file-buffer (directory-file-name dirname))))
+        (setq buffer (dired--create-buffer dirname)))
     (set-buffer buffer)
     (if (not new-buffer-p)             ; existing buffer ...
        (cond (switches                 ; ... but new switches
diff --git a/lisp/files.el b/lisp/files.el
index d325729bf4d..75495ab608e 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -2062,22 +2062,27 @@ find-alternate-file
          (kill-buffer obuf))))))
 
 ;; FIXME we really need to fold the uniquify stuff in here by default,
-;; not using advice, and add it to the doc string.
-(defun create-file-buffer (filename)
+(defun create-file-buffer (filename &optional basename)
   "Create a suitably named buffer for visiting FILENAME, and return it.
 FILENAME (sans directory) is used unchanged if that name is free;
-otherwise a string <2> or <3> or ... is appended to get an unused name.
+otherwise the buffer is renamed according to
+`uniquify-buffer-name-style' to get an unused name.
 
 Emacs treats buffers whose names begin with a space as internal buffers.
 To avoid confusion when visiting a file whose name begins with a space,
-this function prepends a \"|\" to the final result if necessary."
+this function prepends a \"|\" to the final result if necessary.
+
+If BASENAME is non-nil, it will be used as the buffer name.
+FILENAME will only be used to rename the buffer according to
+`uniquify-buffer-name-style' to get an unused name.
+"
   (let* ((lastname (file-name-nondirectory filename))
         (lastname (if (string= lastname "")
                       filename lastname))
-        (buf (generate-new-buffer (if (string-prefix-p " " lastname)
+        (buf (generate-new-buffer (or basename (if (string-prefix-p " " 
lastname)
                                       (concat "|" lastname)
-                                    lastname))))
-    (uniquify--create-file-buffer-advice buf filename)
+                                    lastname)))))
+    (uniquify--create-file-buffer-advice buf filename basename)
     buf))
 
 (defvar abbreviated-home-dir nil
diff --git a/lisp/uniquify.el b/lisp/uniquify.el
index dee9ecba2ea..6c0f5468faa 100644
--- a/lisp/uniquify.el
+++ b/lisp/uniquify.el
@@ -147,12 +147,14 @@ uniquify-separator
 file name components (default \"\\\")."
   :type '(choice (const nil) string))
 
-(defcustom uniquify-trailing-separator-p nil
-  "If non-nil, add a file name separator to dired buffer names.
-If `uniquify-buffer-name-style' is `forward', add the separator at the end;
-if it is `reverse', add the separator at the beginning; otherwise, this
-variable is ignored."
-  :type 'boolean)
+(defvaralias
+ 'uniquify-trailing-separator-p
+ 'dired-trailing-separator)
+
+(make-obsolete-variable
+ 'uniquify-trailing-separator-p
+ 'dired-trailing-separator
+ "30.1")
 
 (defcustom uniquify-strip-common-suffix
   ;; Using it when uniquify-min-dir-content>0 doesn't make much sense.
@@ -174,8 +176,8 @@ uniquify-list-buffers-directory-modes
 (cl-defstruct (uniquify-item
            (:constructor nil) (:copier nil)
            (:constructor uniquify-make-item
-            (base dirname buffer &optional proposed original-dirname)))
-  base dirname buffer proposed original-dirname)
+            (base dirname buffer &optional proposed)))
+  base dirname buffer proposed)
 
 ;; Internal variables used free
 (defvar uniquify-possibly-resolvable nil)
@@ -211,7 +213,7 @@ uniquify-rationalize-file-buffer-names
   (when dirname
     (setq dirname (expand-file-name (directory-file-name dirname)))
     (let ((fix-list (list (uniquify-make-item base dirname newbuf
-                                              nil dirname)))
+                                              nil)))
          items)
       (dolist (buffer (buffer-list))
        (when (and (not (and uniquify-ignore-buffers-re
@@ -292,8 +294,7 @@ uniquify-rationalize
       (setf (uniquify-item-proposed item)
            (uniquify-get-proposed-name (uniquify-item-base item)
                                        (uniquify-item-dirname item)
-                                        nil
-                                        (uniquify-item-original-dirname item)))
+                                        nil))
       (setq uniquify-managed fix-list)))
   ;; Strip any shared last directory names of the dirname.
   (when (and (cdr fix-list) uniquify-strip-common-suffix)
@@ -316,8 +317,7 @@ uniquify-rationalize
                                              (uniquify-item-dirname item))))
                                      (and f (directory-file-name f)))
                                    (uniquify-item-buffer item)
-                                   (uniquify-item-proposed item)
-                                    (uniquify-item-original-dirname item))
+                                   (uniquify-item-proposed item))
                fix-list)))))
   ;; If uniquify-min-dir-content is 0, this will end up just
   ;; passing fix-list to uniquify-rationalize-conflicting-sublist.
@@ -345,21 +345,10 @@ uniquify-rationalize-a-list
     (uniquify-rationalize-conflicting-sublist conflicting-sublist
                                              old-proposed depth)))
 
-(defun uniquify-get-proposed-name (base dirname &optional depth
-                                        original-dirname)
+(defun uniquify-get-proposed-name (base dirname &optional depth)
   (unless depth (setq depth uniquify-min-dir-content))
   (cl-assert (equal (directory-file-name dirname) dirname)) ;No trailing slash.
 
-  ;; Distinguish directories by adding extra separator.
-  (if (and uniquify-trailing-separator-p
-          (file-directory-p (expand-file-name base original-dirname))
-          (not (string-equal base "")))
-      (cond ((eq uniquify-buffer-name-style 'forward)
-            (setq base (file-name-as-directory base)))
-           ;; (setq base (concat base "/")))
-           ((eq uniquify-buffer-name-style 'reverse)
-            (setq base (concat (or uniquify-separator "\\") base)))))
-
   (let ((extra-string nil)
        (n depth))
     (while (and (> n 0) dirname)
@@ -421,8 +410,7 @@ uniquify-rationalize-conflicting-sublist
                  (uniquify-get-proposed-name
                   (uniquify-item-base item)
                   (uniquify-item-dirname item)
-                  depth
-                   (uniquify-item-original-dirname item))))
+                  depth)))
          (uniquify-rationalize-a-list conf-list depth))
       (unless (string= old-name "")
        (uniquify-rename-buffer (car conf-list) old-name)))))
@@ -492,15 +480,14 @@ uniquify--rename-buffer-advice
 
 
 ;; (advice-add 'create-file-buffer :around 
#'uniquify--create-file-buffer-advice)
-(defun uniquify--create-file-buffer-advice (buf filename)
+(defun uniquify--create-file-buffer-advice (buf filename basename)
   ;; BEWARE: This is called directly from `files.el'!
   "Uniquify buffer names with parts of directory name."
   (when uniquify-buffer-name-style
-    (let ((filename (expand-file-name (directory-file-name filename))))
-      (uniquify-rationalize-file-buffer-names
-       (file-name-nondirectory filename)
-       (file-name-directory filename)
-       buf))))
+    (uniquify-rationalize-file-buffer-names
+     (or basename (file-name-nondirectory filename))
+     (file-name-directory (expand-file-name (directory-file-name filename)))
+     buf)))
 
 (defun uniquify-unload-function ()
   "Unload the uniquify library."
diff --git a/test/lisp/uniquify-tests.el b/test/lisp/uniquify-tests.el
new file mode 100644
index 00000000000..70f7125cbe9
--- /dev/null
+++ b/test/lisp/uniquify-tests.el
@@ -0,0 +1,111 @@
+;;; uniquify-tests.el --- Tests for uniquify         -*- lexical-binding: t; 
-*-
+
+;; Copyright (C) 2023 Free Software Foundation, Inc.
+
+;; Author: Spencer Baugh <sbaugh@janestreet.com>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'ert)
+
+(ert-deftest uniquify-basic ()
+  (let (bufs old-names)
+    (cl-flet ((names-are (current-names &optional nosave)
+                (should (equal (mapcar #'buffer-name bufs) current-names))
+                (unless nosave (push current-names old-names))))
+      (should (eq (get-buffer "z") nil))
+      (push (find-file-noselect "a/b/z") bufs)
+      (names-are '("z"))
+      (push (find-file-noselect "a/b/c/z") bufs)
+      (names-are '("z<c>" "z<b>"))
+      (push (find-file-noselect "a/b/d/z") bufs)
+      (names-are '("z<d>" "z<c>" "z<b>"))
+      (push (find-file-noselect "e/b/z") bufs)
+      (names-are '("z<e/b>" "z<d>" "z<c>" "z<a/b>"))
+      ;; buffers without a buffer-file-name don't get uniquified by uniquify
+      (push (generate-new-buffer "z") bufs)
+      (names-are '("z" "z<e/b>" "z<d>" "z<c>" "z<a/b>"))
+      ;; but they do get uniquified by the C code which uses <n>
+      (push (generate-new-buffer "z") bufs)
+      (names-are '("z<2>" "z" "z<e/b>" "z<d>" "z<c>" "z<a/b>"))
+      (save-excursion
+        ;; uniquify will happily work with file-visiting buffers whose names 
don't match buffer-file-name
+        (find-file "f/y")
+        (push (current-buffer) bufs)
+        (rename-buffer "z" t)
+        (names-are '("z<f>" "z<2>" "z" "z<e/b>" "z<d>" "z<c>" "z<a/b>") 
'nosave)
+        ;; somewhat confusing behavior results if a buffer is renamed to match 
an already-uniquified buffer
+        (rename-buffer "z<a/b>" t)
+        (names-are '("z<a/b><f>" "z<2>" "z" "z<e/b>" "z<d>" "z<c>" "z<a/b>") 
'nosave))
+      (while bufs
+        (kill-buffer (pop bufs))
+        (names-are (pop old-names) 'nosave)))))
+
+(ert-deftest uniquify-dirs ()
+  "Check strip-common-suffix and trailing-separator-p work together; bug#47132"
+  (let* ((root (make-temp-file "emacs-uniquify-tests" 'dir))
+         (a-path (file-name-concat root "a/x/y/dir"))
+         (b-path (file-name-concat root "b/x/y/dir")))
+    (make-directory a-path 'parents)
+    (make-directory b-path 'parents)
+    (let ((uniquify-buffer-name-style 'forward)
+          (uniquify-strip-common-suffix t)
+          (uniquify-trailing-separator-p nil))
+      (let ((bufs (list (find-file-noselect a-path)
+                       (find-file-noselect b-path))))
+        (should (equal (mapcar #'buffer-name bufs)
+                       '("a/dir" "b/dir")))
+        (mapc #'kill-buffer bufs)))
+    (let ((uniquify-buffer-name-style 'forward)
+          (uniquify-strip-common-suffix nil)
+          (uniquify-trailing-separator-p t))
+      (let ((bufs (list (find-file-noselect a-path)
+                       (find-file-noselect b-path))))
+        (should (equal (mapcar #'buffer-name bufs)
+                       '("a/x/y/dir/" "b/x/y/dir/")))
+        (mapc #'kill-buffer bufs)))
+    (let ((uniquify-buffer-name-style 'forward)
+          (uniquify-strip-common-suffix t)
+          (uniquify-trailing-separator-p t))
+      (let ((bufs (list (find-file-noselect a-path)
+                       (find-file-noselect b-path))))
+        (should (equal (mapcar #'buffer-name bufs)
+                       '("a/dir/" "b/dir/")))
+        (mapc #'kill-buffer bufs)))))
+
+(ert-deftest uniquify-rename-to-dir ()
+  "Giving a buffer a name which matches a directory doesn't rename the buffer"
+  (let ((uniquify-buffer-name-style 'forward)
+        (uniquify-trailing-separator-p t))
+      (save-excursion
+        (find-file "../README")
+        (rename-buffer "lisp" t)
+        (should (equal (buffer-name) "lisp"))
+        (kill-buffer))))
+
+(ert-deftest uniquify-separator-style-reverse ()
+  (let ((uniquify-buffer-name-style 'reverse)
+        (uniquify-trailing-separator-p t))
+    (save-excursion
+      (should (file-directory-p "../lib-src"))
+      (find-file "../lib-src")
+      (should (equal (buffer-name) "\\lib-src"))
+      (kill-buffer))))
+
+(provide 'uniquify-tests)
+;;; uniquify-tests.el ends here