bug#64088: [PATCH] Make project-root for vc projects return an absolute path

[sbaugh]

sbaugh@catern.com writes:
> Dmitry Gutov <dmitry@gutov.dev> writes:
>> On 11/07/2023 02:45, Spencer Baugh wrote:
>>> Dmitry Gutov <dmitry@gutov.dev> writes:
>>>> On 27/06/2023 23:01, Spencer Baugh wrote:
>>>>> OK, how about this?
>>>>
>>>> Maybe we should go in the other direction? And call
>>>> abbreviate-file-name on them?
>>>>
>>>> Because otherwise in project-prompt-project-dir we'll always show the
>>>> expanded directory names, taking up extra space and usually repeating
>>>> the full name of the user's home directory for no good reason.
>>> That seems reasonable if we let-bind directory-abbrev-alist to nil
>>> around it; otherwise we'll be dependent on the user's configuration and
>>> we might add a directory in one way, and then they add a new value to
>>> directory-abbrev-alist and we add it again a second way.
>>
>> That's also fair.
>>
>>> Although maybe that's fine?  And probably users of
>>> directory-abbrev-alist would like to have those abbreviations show up in
>>> project-prompt-project-dir.
>>
>> They probably would. But indeed if the list was saved with one
>> configuration, and read with another, it could lead to a mistake.
>>
>>> Also we could always call abbreviate-file-name at
>>> project-prompt-project-dir time.
>>
>> Meaning it will be called N times (for the number of projects) every
>> time the list is displayed, instead of just once, when the project is
>> saved/visited. But maybe it's fine too? How slow could that be?
>
> I was sad about this but I think I've got the solution now: We just
> maintain project--list in abbreviated form and project-list-file in
> expanded form.
>
> I think that solves all the problems: the persistent file is independent
> of user configuration, so if the user changes their abbreviations
> they'll get new ones the next time the file is read (presumably the next
> time they run Emacs).  But project--list is abbreviated, so
> project-prompt-project-dir gets abbreviated dirs.
>
> It does mean that if they change their directory-abbrev-alist while
> Emacs is running they could get duplicate entries, but that already
> could happen before this patch, and it's not a big problem IMO.
>
> See patch below.

Oops, this patch needed a few tweaks.  Especially, skipping the
expansion and abbreviation for remote files, to avoid making unnecesary
remote connections.

>From 9523b4dea1234083e65b141a281c1108f52b046b Mon Sep 17 00:00:00 2001
From: Spencer Baugh <sbaugh@catern.com>
Date: Sat, 19 Aug 2023 08:24:45 -0400
Subject: [PATCH] Expand project file names before storing them

Before, whatever project-root returned, we stored as the root
directory of the project in project-list and project-list-file.  This
could lead to duplicate entries or bad behavior if projects were
accessed by different file names, e.g. both /home/user/src/emacs and
~/src/emacs.

Now project-list-file contains only expanded paths and project--list
contains only abbreviated paths.  We abbreviate filenames before
setting project--list, and expand filenames before writing to
project-list-file.  We only do this for local files, though, to avoid
making remote connections; the situation will still be bad for remote
projects, but at least this is an improvement.

* lisp/progmodes/project.el (project--write-project-list): Call
expand-file-name.
(project--read-project-list, project-remember-project)
(project--remove-from-project-list): Call abbreviate-file-name.
---
 lisp/progmodes/project.el | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 11fa93fb70d..21d5df8f0cc 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1586,7 +1586,12 @@ project--read-project-list
           (when (file-exists-p filename)
             (with-temp-buffer
               (insert-file-contents filename)
-              (read (current-buffer)))))
+              (mapcar
+               (lambda (elem)
+                 (let ((name (car elem)))
+                   (list (if (file-remote-p name) name
+                           (abbreviate-file-name name)))))
+               (read (current-buffer))))))
     (unless (seq-every-p
              (lambda (elt) (stringp (car-safe elt)))
              project--list)
@@ -1606,7 +1611,12 @@ project--write-project-list
       (insert ";;; -*- lisp-data -*-\n")
       (let ((print-length nil)
             (print-level nil))
-        (pp project--list (current-buffer)))
+        (pp (mapcar (lambda (elem)
+                      (let ((name (car elem)))
+                        (list (if (file-remote-p name) name
+                                (expand-file-name name)))))
+                    project--list)
+            (current-buffer)))
       (write-region nil nil filename nil 'silent))))
 
 ;;;###autoload
@@ -1615,7 +1625,7 @@ project-remember-project
 Save the result in `project-list-file' if the list of projects
 has changed, and NO-WRITE is nil."
   (project--ensure-read-project-list)
-  (let ((dir (project-root pr)))
+  (let ((dir (abbreviate-file-name (project-root pr))))
     (unless (equal (caar project--list) dir)
       (dolist (ent project--list)
         (when (equal dir (car ent))
@@ -1631,7 +1641,7 @@ project--remove-from-project-list
 from the list using REPORT-MESSAGE, which is a format string
 passed to `message' as its first argument."
   (project--ensure-read-project-list)
-  (when-let ((ent (assoc project-root project--list)))
+  (when-let ((ent (assoc (abbreviate-file-name project-root) project--list)))
     (setq project--list (delq ent project--list))
     (message report-message project-root)
     (project--write-project-list)))
-- 
2.41.0