bug#62621: 29.0.60; uniquify can't make buffers unique based on things other than filename

[sbaugh]

OK, after resolving bug#62732, now at last my nice and short patch for
this feature.

I've thought quite a bit about how to make this configurable, and I
think just letting people write their own arbitrary transformation
functions, as I do in this patch, is what we should provide.  Making
things any more modular is fairly difficult.  Packages can come along
and provide other fancy functions if they like.

>From 5e6260951b31fbd9da826cc2ff56bfbecdbbe7eb Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@catern.com>
Date: Sun, 9 Jul 2023 22:21:03 -0400
Subject: [PATCH] Support transforming the dirname used by uniquify

By transforming the dirname, we can add additional information to use
during uniquifying.  A basic one: uniquifying buffer names based on
the project name.

* lisp/progmodes/project.el (project-uniquify-dirname-transform): Add.
* lisp/uniquify.el (uniquify-dirname-transform-default)
(uniquify-dirname-transform): Add. (bug#62621)
(uniquify-rationalize-file-buffer-names, uniquify-buffer-file-name):
Use uniquify-dirname-transform.
* test/lisp/uniquify-tests.el (uniquify-home,
uniquify-project-transform): Add tests.
---
 lisp/progmodes/project.el   | 12 ++++++++++++
 lisp/uniquify.el            | 22 +++++++++++++++++-----
 test/lisp/uniquify-tests.el | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 03ed966cc45..11fa93fb70d 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1887,5 +1887,17 @@ project-switch-project
     (let ((project-current-directory-override dir))
       (call-interactively command))))
 
+;;;###autoload
+(defun project-uniquify-dirname-transform (dirname)
+  "Include `project-name' in DIRNAME if in a project."
+  (if-let (proj (project-current nil dirname))
+      (let ((root (project-root proj)))
+        (expand-file-name
+         (file-name-concat
+          (file-name-directory root)
+          (project-name proj)
+          (file-relative-name dirname root))))
+    dirname))
+
 (provide 'project)
 ;;; project.el ends here
diff --git a/lisp/uniquify.el b/lisp/uniquify.el
index d1ca455b673..bd49346da45 100644
--- a/lisp/uniquify.el
+++ b/lisp/uniquify.el
@@ -168,6 +168,16 @@ uniquify-list-buffers-directory-modes
 That means that when `buffer-file-name' is set to nil, `list-buffers-directory'
 contains the name of the directory which the buffer is visiting.")
 
+(defcustom uniquify-dirname-transform #'identity
+  "A function to transform the dirname used to uniquify a buffer.
+
+It takes a single argument: the directory of the buffer.  It
+should return a string filename (which does not need to actually
+exist in the filesystem) to use for uniquifying the buffer name."
+  :type '(choice (function-item :tag "Don't change the dirname" identity)
+                 function)
+  :group 'uniquify)
+
 ;;; Utilities
 
 ;; uniquify-fix-list data structure
@@ -209,7 +219,8 @@ uniquify-rationalize-file-buffer-names
   ;; this buffer.
   (with-current-buffer newbuf (setq uniquify-managed nil))
   (when dirname
-    (setq dirname (expand-file-name (directory-file-name dirname)))
+    (setq dirname (funcall uniquify-dirname-transform
+                           (expand-file-name (directory-file-name dirname))))
     (let ((fix-list (list (uniquify-make-item base dirname newbuf
                                               nil)))
          items)
@@ -268,10 +279,11 @@ uniquify-buffer-file-name
               (if (memq major-mode uniquify-list-buffers-directory-modes)
                   list-buffers-directory))))
       (when filename
-       (directory-file-name
-        (file-name-directory
-         (expand-file-name
-          (directory-file-name filename))))))))
+        (funcall uniquify-dirname-transform
+                 (directory-file-name
+                 (file-name-directory
+                  (expand-file-name
+                   (directory-file-name filename)))))))))
 
 (defun uniquify-rerationalize-w/o-cb (fix-list)
   "Re-rationalize the buffers in FIX-LIST, but ignoring `current-buffer'."
diff --git a/test/lisp/uniquify-tests.el b/test/lisp/uniquify-tests.el
index abd61fa3504..e533c4b644c 100644
--- a/test/lisp/uniquify-tests.el
+++ b/test/lisp/uniquify-tests.el
@@ -88,6 +88,21 @@ uniquify-dirs
                        '("a/dir/" "b/dir/")))
         (mapc #'kill-buffer bufs)))))
 
+(ert-deftest uniquify-home ()
+  "uniquify works, albeit confusingly, in the presence of directories named 
\"~\""
+  (let (bufs)
+    (save-excursion
+      (push (find-file-noselect "~") bufs)
+      (push (find-file-noselect "./~") bufs)
+      (should (equal (mapcar #'buffer-name bufs)
+                     '("~<test>" "~<>")))
+      (push (find-file-noselect "~/foo") bufs)
+      (push (find-file-noselect "./~/foo") bufs)
+      (should (equal (mapcar #'buffer-name bufs)
+                     '("foo<~>" "foo</nonexistent>" "~<test>" "~<>")))
+      (while bufs
+        (kill-buffer (pop 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)
@@ -125,5 +140,23 @@ uniquify-space-prefix
     (should (equal (buffer-name) "| foo"))
     (kill-buffer)))
 
+(require 'project)
+(ert-deftest uniquify-project-transform ()
+  "`project-uniquify-dirname-transform' works"
+  (let ((uniquify-dirname-transform #'project-uniquify-dirname-transform)
+        (project-vc-name "foo1/bar")
+        bufs)
+    (save-excursion
+      (should (file-exists-p "../README"))
+      (push (find-file-noselect "../README") bufs)
+      (push (find-file-noselect "other/README") bufs)
+      (should (equal (mapcar #'buffer-name bufs)
+                     '("README<other>" "README<bar>")))
+      (push (find-file-noselect "foo2/bar/README") bufs)
+      (should (equal (mapcar #'buffer-name bufs)
+                     '("README<foo2/bar>" "README<other>" "README<foo1/bar>")))
+      (while bufs
+        (kill-buffer (pop bufs))))))
+
 (provide 'uniquify-tests)
 ;;; uniquify-tests.el ends here
-- 
2.41.0